[RTL] Add support for shaping in background thread.

2 files changed, 594 insertions, 285 deletions

diff --git a/scene/gui/rich_text_label.cpp b/scene/gui/rich_text_label.cpp
index fa0c2ce12c..78fd682c35 100644
--- a/scene/gui/rich_text_label.cpp
+++ b/scene/gui/rich_text_label.cpp
@@ -209,9 +209,10 @@ String RichTextLabel::_letters(int p_num, bool p_capitalize) const {
 
 void RichTextLabel::_update_line_font(ItemFrame *p_frame, int p_line, const Ref<Font> &p_base_font, int p_base_font_size) {
 	ERR_FAIL_COND(p_frame == nullptr);
-	ERR_FAIL_COND(p_line < 0 || p_line >= p_frame->lines.size());
+	ERR_FAIL_COND(p_line < 0 || p_line >= (int)p_frame->lines.size());
 
-	Line &l = p_frame->lines.write[p_line];
+	Line &l = p_frame->lines[p_line];
+	MutexLock lock(l.text_buf->get_mutex());
 
 	RID t = l.text_buf->get_rid();
 	int spans = TS->shaped_get_span_count(t);
@@ -231,7 +232,7 @@ void RichTextLabel::_update_line_font(ItemFrame *p_frame, int p_line, const Ref<
 		}
 	}
 
-	Item *it_to = (p_line + 1 < p_frame->lines.size()) ? p_frame->lines[p_line + 1].from : nullptr;
+	Item *it_to = (p_line + 1 < (int)p_frame->lines.size()) ? p_frame->lines[p_line + 1].from : nullptr;
 	for (Item *it = l.from; it && it != it_to; it = _get_next_item(it)) {
 		switch (it->type) {
 			case ITEM_TABLE: {
@@ -239,7 +240,7 @@ void RichTextLabel::_update_line_font(ItemFrame *p_frame, int p_line, const Ref<
 				for (Item *E : table->subitems) {
 					ERR_CONTINUE(E->type != ITEM_FRAME); // Children should all be frames.
 					ItemFrame *frame = static_cast<ItemFrame *>(E);
-					for (int i = 0; i < frame->lines.size(); i++) {
+					for (int i = 0; i < (int)frame->lines.size(); i++) {
 						_update_line_font(frame, i, p_base_font, p_base_font_size);
 					}
 				}
@@ -250,11 +251,12 @@ void RichTextLabel::_update_line_font(ItemFrame *p_frame, int p_line, const Ref<
 	}
 }
 
-void RichTextLabel::_resize_line(ItemFrame *p_frame, int p_line, const Ref<Font> &p_base_font, int p_base_font_size, int p_width) {
-	ERR_FAIL_COND(p_frame == nullptr);
-	ERR_FAIL_COND(p_line < 0 || p_line >= p_frame->lines.size());
+float RichTextLabel::_resize_line(ItemFrame *p_frame, int p_line, const Ref<Font> &p_base_font, int p_base_font_size, int p_width, float p_h) {
+	ERR_FAIL_COND_V(p_frame == nullptr, p_h);
+	ERR_FAIL_COND_V(p_line < 0 || p_line >= (int)p_frame->lines.size(), p_h);
 
-	Line &l = p_frame->lines.write[p_line];
+	Line &l = p_frame->lines[p_line];
+	MutexLock lock(l.text_buf->get_mutex());
 
 	l.offset.x = _find_margin(l.from, p_base_font, p_base_font_size);
 	l.text_buf->set_width(p_width - l.offset.x);
@@ -265,7 +267,7 @@ void RichTextLabel::_resize_line(ItemFrame *p_frame, int p_line, const Ref<Font>
 		l.text_buf->tab_align(tabs);
 	}
 
-	Item *it_to = (p_line + 1 < p_frame->lines.size()) ? p_frame->lines[p_line + 1].from : nullptr;
+	Item *it_to = (p_line + 1 < (int)p_frame->lines.size()) ? p_frame->lines[p_line + 1].from : nullptr;
 	for (Item *it = l.from; it && it != it_to; it = _get_next_item(it)) {
 		switch (it->type) {
 			case ITEM_TABLE: {
@@ -275,16 +277,18 @@ void RichTextLabel::_resize_line(ItemFrame *p_frame, int p_line, const Ref<Font>
 				int col_count = table->columns.size();
 
 				for (int i = 0; i < col_count; i++) {
-					table->columns.write[i].width = 0;
+					table->columns[i].width = 0;
 				}
 
 				int idx = 0;
 				for (Item *E : table->subitems) {
 					ERR_CONTINUE(E->type != ITEM_FRAME); // Children should all be frames.
 					ItemFrame *frame = static_cast<ItemFrame *>(E);
-					for (int i = 0; i < frame->lines.size(); i++) {
+					float prev_h = 0;
+					for (int i = 0; i < (int)frame->lines.size(); i++) {
+						MutexLock sub_lock(frame->lines[i].text_buf->get_mutex());
 						int w = _find_margin(frame->lines[i].from, p_base_font, p_base_font_size) + 1;
-						_resize_line(frame, i, p_base_font, p_base_font_size, w);
+						prev_h = _resize_line(frame, i, p_base_font, p_base_font_size, w, prev_h);
 					}
 					idx++;
 				}
@@ -300,7 +304,7 @@ void RichTextLabel::_resize_line(ItemFrame *p_frame, int p_line, const Ref<Font>
 				for (int i = 0; i < col_count; i++) {
 					remaining_width -= table->columns[i].min_width;
 					if (table->columns[i].max_width > table->columns[i].min_width) {
-						table->columns.write[i].expand = true;
+						table->columns[i].expand = true;
 					}
 					if (table->columns[i].expand) {
 						total_ratio += table->columns[i].expand_ratio;
@@ -309,9 +313,9 @@ void RichTextLabel::_resize_line(ItemFrame *p_frame, int p_line, const Ref<Font>
 
 				// Assign actual widths.
 				for (int i = 0; i < col_count; i++) {
-					table->columns.write[i].width = table->columns[i].min_width;
+					table->columns[i].width = table->columns[i].min_width;
 					if (table->columns[i].expand && total_ratio > 0 && remaining_width > 0) {
-						table->columns.write[i].width += table->columns[i].expand_ratio * remaining_width / total_ratio;
+						table->columns[i].width += table->columns[i].expand_ratio * remaining_width / total_ratio;
 					}
 					table->total_width += table->columns[i].width + hseparation;
 				}
@@ -328,7 +332,7 @@ void RichTextLabel::_resize_line(ItemFrame *p_frame, int p_line, const Ref<Font>
 						int dif = table->columns[i].width - table->columns[i].max_width;
 						if (dif > 0) {
 							table_need_fit = true;
-							table->columns.write[i].width = table->columns[i].max_width;
+							table->columns[i].width = table->columns[i].max_width;
 							table->total_width -= dif;
 							total_ratio -= table->columns[i].expand_ratio;
 						}
@@ -342,7 +346,7 @@ void RichTextLabel::_resize_line(ItemFrame *p_frame, int p_line, const Ref<Font>
 								if (dif > 0) {
 									int slice = table->columns[i].expand_ratio * remaining_width / total_ratio;
 									int incr = MIN(dif, slice);
-									table->columns.write[i].width += incr;
+									table->columns[i].width += incr;
 									table->total_width += incr;
 								}
 							}
@@ -366,16 +370,14 @@ void RichTextLabel::_resize_line(ItemFrame *p_frame, int p_line, const Ref<Font>
 
 					offset.x += frame->padding.position.x;
 					float yofs = frame->padding.position.y;
-					for (int i = 0; i < frame->lines.size(); i++) {
-						frame->lines.write[i].text_buf->set_width(table->columns[column].width);
-						table->columns.write[column].width = MAX(table->columns.write[column].width, ceil(frame->lines[i].text_buf->get_size().x));
+					float prev_h = 0;
+					for (int i = 0; i < (int)frame->lines.size(); i++) {
+						MutexLock sub_lock(frame->lines[i].text_buf->get_mutex());
+						frame->lines[i].text_buf->set_width(table->columns[column].width);
+						table->columns[column].width = MAX(table->columns[column].width, ceil(frame->lines[i].text_buf->get_size().x));
 
-						if (i > 0) {
-							frame->lines.write[i].offset.y = frame->lines[i - 1].offset.y + frame->lines[i - 1].text_buf->get_size().y + frame->lines[i - 1].text_buf->get_line_count() * get_theme_constant(SNAME("line_separation"));
-						} else {
-							frame->lines.write[i].offset.y = 0;
-						}
-						frame->lines.write[i].offset += offset;
+						frame->lines[i].offset.y = prev_h;
+						frame->lines[i].offset += offset;
 
 						float h = frame->lines[i].text_buf->get_size().y + (frame->lines[i].text_buf->get_line_count() - 1) * get_theme_constant(SNAME("line_separation"));
 						if (i > 0) {
@@ -388,6 +390,7 @@ void RichTextLabel::_resize_line(ItemFrame *p_frame, int p_line, const Ref<Font>
 							h = MIN(h, frame->max_size_over.y);
 						}
 						yofs += h;
+						prev_h = frame->lines[i].offset.y + frame->lines[i].text_buf->get_size().y + frame->lines[i].text_buf->get_line_count() * get_theme_constant(SNAME("line_separation"));
 					}
 					yofs += frame->padding.size.y;
 					offset.x += table->columns[column].width + hseparation + frame->padding.size.x;
@@ -410,18 +413,16 @@ void RichTextLabel::_resize_line(ItemFrame *p_frame, int p_line, const Ref<Font>
 		}
 	}
 
-	if (p_line > 0) {
-		l.offset.y = p_frame->lines[p_line - 1].offset.y + p_frame->lines[p_line - 1].text_buf->get_size().y + p_frame->lines[p_line - 1].text_buf->get_line_count() * get_theme_constant(SNAME("line_separation"));
-	} else {
-		l.offset.y = 0;
-	}
+	l.offset.y = p_h;
+	return l.offset.y + l.text_buf->get_size().y + l.text_buf->get_line_count() * get_theme_constant(SNAME("line_separation"));
 }
 
-void RichTextLabel::_shape_line(ItemFrame *p_frame, int p_line, const Ref<Font> &p_base_font, int p_base_font_size, int p_width, int *r_char_offset) {
-	ERR_FAIL_COND(p_frame == nullptr);
-	ERR_FAIL_COND(p_line < 0 || p_line >= p_frame->lines.size());
+float RichTextLabel::_shape_line(ItemFrame *p_frame, int p_line, const Ref<Font> &p_base_font, int p_base_font_size, int p_width, float p_h, int *r_char_offset) {
+	ERR_FAIL_COND_V(p_frame == nullptr, p_h);
+	ERR_FAIL_COND_V(p_line < 0 || p_line >= (int)p_frame->lines.size(), p_h);
 
-	Line &l = p_frame->lines.write[p_line];
+	Line &l = p_frame->lines[p_line];
+	MutexLock lock(l.text_buf->get_mutex());
 
 	uint16_t autowrap_flags = TextServer::BREAK_MANDATORY;
 	switch (autowrap_mode) {
@@ -458,7 +459,7 @@ void RichTextLabel::_shape_line(ItemFrame *p_frame, int p_line, const Ref<Font>
 
 	// Shape current paragraph.
 	String text;
-	Item *it_to = (p_line + 1 < p_frame->lines.size()) ? p_frame->lines[p_line + 1].from : nullptr;
+	Item *it_to = (p_line + 1 < (int)p_frame->lines.size()) ? p_frame->lines[p_line + 1].from : nullptr;
 	int remaining_characters = visible_characters - l.char_offset;
 	for (Item *it = l.from; it && it != it_to; it = _get_next_item(it)) {
 		if (visible_chars_behavior == VC_CHARS_BEFORE_SHAPING && visible_characters >= 0 && remaining_characters <= 0) {
@@ -524,9 +525,9 @@ void RichTextLabel::_shape_line(ItemFrame *p_frame, int p_line, const Ref<Font>
 				int t_char_count = 0;
 				// Set minimums to zero.
 				for (int i = 0; i < col_count; i++) {
-					table->columns.write[i].min_width = 0;
-					table->columns.write[i].max_width = 0;
-					table->columns.write[i].width = 0;
+					table->columns[i].min_width = 0;
+					table->columns[i].max_width = 0;
+					table->columns[i].width = 0;
 				}
 				// Compute minimum width for each cell.
 				const int available_width = p_width - hseparation * (col_count - 1);
@@ -537,17 +538,20 @@ void RichTextLabel::_shape_line(ItemFrame *p_frame, int p_line, const Ref<Font>
 					ItemFrame *frame = static_cast<ItemFrame *>(E);
 
 					int column = idx % col_count;
-					for (int i = 0; i < frame->lines.size(); i++) {
+					float prev_h = 0;
+					for (int i = 0; i < (int)frame->lines.size(); i++) {
+						MutexLock sub_lock(frame->lines[i].text_buf->get_mutex());
+
 						int char_offset = l.char_offset + l.char_count;
 						int w = _find_margin(frame->lines[i].from, p_base_font, p_base_font_size) + 1;
-						_shape_line(frame, i, p_base_font, p_base_font_size, w, &char_offset);
+						prev_h = _shape_line(frame, i, p_base_font, p_base_font_size, w, prev_h, &char_offset);
 						int cell_ch = (char_offset - (l.char_offset + l.char_count));
 						l.char_count += cell_ch;
 						t_char_count += cell_ch;
 						remaining_characters -= cell_ch;
 
-						table->columns.write[column].min_width = MAX(table->columns[column].min_width, ceil(frame->lines[i].text_buf->get_size().x));
-						table->columns.write[column].max_width = MAX(table->columns[column].max_width, ceil(frame->lines[i].text_buf->get_non_wrapped_size().x));
+						table->columns[column].min_width = MAX(table->columns[column].min_width, ceil(frame->lines[i].text_buf->get_size().x));
+						table->columns[column].max_width = MAX(table->columns[column].max_width, ceil(frame->lines[i].text_buf->get_non_wrapped_size().x));
 					}
 					idx++;
 				}
@@ -560,7 +564,7 @@ void RichTextLabel::_shape_line(ItemFrame *p_frame, int p_line, const Ref<Font>
 				for (int i = 0; i < col_count; i++) {
 					remaining_width -= table->columns[i].min_width;
 					if (table->columns[i].max_width > table->columns[i].min_width) {
-						table->columns.write[i].expand = true;
+						table->columns[i].expand = true;
 					}
 					if (table->columns[i].expand) {
 						total_ratio += table->columns[i].expand_ratio;
@@ -569,9 +573,9 @@ void RichTextLabel::_shape_line(ItemFrame *p_frame, int p_line, const Ref<Font>
 
 				// Assign actual widths.
 				for (int i = 0; i < col_count; i++) {
-					table->columns.write[i].width = table->columns[i].min_width;
+					table->columns[i].width = table->columns[i].min_width;
 					if (table->columns[i].expand && total_ratio > 0 && remaining_width > 0) {
-						table->columns.write[i].width += table->columns[i].expand_ratio * remaining_width / total_ratio;
+						table->columns[i].width += table->columns[i].expand_ratio * remaining_width / total_ratio;
 					}
 					table->total_width += table->columns[i].width + hseparation;
 				}
@@ -588,7 +592,7 @@ void RichTextLabel::_shape_line(ItemFrame *p_frame, int p_line, const Ref<Font>
 						int dif = table->columns[i].width - table->columns[i].max_width;
 						if (dif > 0) {
 							table_need_fit = true;
-							table->columns.write[i].width = table->columns[i].max_width;
+							table->columns[i].width = table->columns[i].max_width;
 							table->total_width -= dif;
 							total_ratio -= table->columns[i].expand_ratio;
 						}
@@ -602,7 +606,7 @@ void RichTextLabel::_shape_line(ItemFrame *p_frame, int p_line, const Ref<Font>
 								if (dif > 0) {
 									int slice = table->columns[i].expand_ratio * remaining_width / total_ratio;
 									int incr = MIN(dif, slice);
-									table->columns.write[i].width += incr;
+									table->columns[i].width += incr;
 									table->total_width += incr;
 								}
 							}
@@ -626,16 +630,15 @@ void RichTextLabel::_shape_line(ItemFrame *p_frame, int p_line, const Ref<Font>
 
 					offset.x += frame->padding.position.x;
 					float yofs = frame->padding.position.y;
-					for (int i = 0; i < frame->lines.size(); i++) {
-						frame->lines.write[i].text_buf->set_width(table->columns[column].width);
-						table->columns.write[column].width = MAX(table->columns.write[column].width, ceil(frame->lines[i].text_buf->get_size().x));
+					float prev_h = 0;
+					for (int i = 0; i < (int)frame->lines.size(); i++) {
+						MutexLock sub_lock(frame->lines[i].text_buf->get_mutex());
 
-						if (i > 0) {
-							frame->lines.write[i].offset.y = frame->lines[i - 1].offset.y + frame->lines[i - 1].text_buf->get_size().y + frame->lines[i - 1].text_buf->get_line_count() * get_theme_constant(SNAME("line_separation"));
-						} else {
-							frame->lines.write[i].offset.y = 0;
-						}
-						frame->lines.write[i].offset += offset;
+						frame->lines[i].text_buf->set_width(table->columns[column].width);
+						table->columns[column].width = MAX(table->columns[column].width, ceil(frame->lines[i].text_buf->get_size().x));
+
+						frame->lines[i].offset.y = prev_h;
+						frame->lines[i].offset += offset;
 
 						float h = frame->lines[i].text_buf->get_size().y + (frame->lines[i].text_buf->get_line_count() - 1) * get_theme_constant(SNAME("line_separation"));
 						if (i > 0) {
@@ -648,6 +651,7 @@ void RichTextLabel::_shape_line(ItemFrame *p_frame, int p_line, const Ref<Font>
 							h = MIN(h, frame->max_size_over.y);
 						}
 						yofs += h;
+						prev_h = frame->lines[i].offset.y + frame->lines[i].text_buf->get_size().y + frame->lines[i].text_buf->get_line_count() * get_theme_constant(SNAME("line_separation"));
 					}
 					yofs += frame->padding.size.y;
 					offset.x += table->columns[column].width + hseparation + frame->padding.size.x;
@@ -678,24 +682,22 @@ void RichTextLabel::_shape_line(ItemFrame *p_frame, int p_line, const Ref<Font>
 
 	*r_char_offset = l.char_offset + l.char_count;
 
-	if (p_line > 0) {
-		l.offset.y = p_frame->lines[p_line - 1].offset.y + p_frame->lines[p_line - 1].text_buf->get_size().y + p_frame->lines[p_line - 1].text_buf->get_line_count() * get_theme_constant(SNAME("line_separation"));
-	} else {
-		l.offset.y = 0;
-	}
+	l.offset.y = p_h;
+	return l.offset.y + l.text_buf->get_size().y + l.text_buf->get_line_count() * get_theme_constant(SNAME("line_separation"));
 }
 
 int RichTextLabel::_draw_line(ItemFrame *p_frame, int p_line, const Vector2 &p_ofs, int p_width, const Color &p_base_color, int p_outline_size, const Color &p_outline_color, const Color &p_font_shadow_color, int p_shadow_outline_size, const Point2 &p_shadow_ofs, int &r_processed_glyphs) {
 	ERR_FAIL_COND_V(p_frame == nullptr, 0);
-	ERR_FAIL_COND_V(p_line < 0 || p_line >= p_frame->lines.size(), 0);
+	ERR_FAIL_COND_V(p_line < 0 || p_line >= (int)p_frame->lines.size(), 0);
 
 	Vector2 off;
 	int line_spacing = get_theme_constant(SNAME("line_separation"));
 
-	Line &l = p_frame->lines.write[p_line];
+	Line &l = p_frame->lines[p_line];
+	MutexLock lock(l.text_buf->get_mutex());
 
 	Item *it_from = l.from;
-	Item *it_to = (p_line + 1 < p_frame->lines.size()) ? p_frame->lines[p_line + 1].from : nullptr;
+	Item *it_to = (p_line + 1 < (int)p_frame->lines.size()) ? p_frame->lines[p_line + 1].from : nullptr;
 
 	if (it_from == nullptr) {
 		return 0;
@@ -877,7 +879,7 @@ int RichTextLabel::_draw_line(ItemFrame *p_frame, int p_line, const Vector2 &p_o
 								draw_rect(Rect2(p_ofs + rect.position + off + coff - frame->padding.position, Size2(table->columns[col].width + hseparation + frame->padding.position.x + frame->padding.size.x, table->rows[row])), (frame->border != Color(0, 0, 0, 0) ? frame->border : border), false);
 							}
 
-							for (int j = 0; j < frame->lines.size(); j++) {
+							for (int j = 0; j < (int)frame->lines.size(); j++) {
 								_draw_line(frame, j, p_ofs + rect.position + off + Vector2(0, frame->lines[j].offset.y), rect.size.x, p_base_color, p_outline_size, p_outline_color, p_font_shadow_color, p_shadow_outline_size, p_shadow_ofs, r_processed_glyphs);
 							}
 							idx++;
@@ -1299,22 +1301,12 @@ void RichTextLabel::_find_click(ItemFrame *p_frame, const Point2i &p_click, Item
 	int vofs = vscroll->get_value();
 
 	// Search for the first line.
-	int from_line = 0;
-
-	//TODO, change to binary search ?
-	while (from_line < main->lines.size()) {
-		if (main->lines[from_line].offset.y + main->lines[from_line].text_buf->get_size().y + main->lines[from_line].text_buf->get_line_count() * get_theme_constant(SNAME("line_separation")) >= vofs) {
-			break;
-		}
-		from_line++;
-	}
-
-	if (from_line >= main->lines.size()) {
-		return;
-	}
+	int to_line = main->first_invalid_line.load();
+	int from_line = _find_first_line(0, to_line, vofs);
 
 	Point2 ofs = text_rect.get_position() + Vector2(0, main->lines[from_line].offset.y - vofs);
-	while (ofs.y < size.height && from_line < main->lines.size()) {
+	while (ofs.y < size.height && from_line < to_line) {
+		MutexLock lock(main->lines[from_line].text_buf->get_mutex());
 		_find_click_in_line(p_frame, from_line, ofs, text_rect.size.x, p_click, r_click_frame, r_click_line, r_click_item, r_click_char);
 		ofs.y += main->lines[from_line].text_buf->get_size().y + main->lines[from_line].text_buf->get_line_count() * get_theme_constant(SNAME("line_separation"));
 		if (((r_click_item != nullptr) && ((*r_click_item) != nullptr)) || ((r_click_frame != nullptr) && ((*r_click_frame) != nullptr))) {
@@ -1331,7 +1323,9 @@ float RichTextLabel::_find_click_in_line(ItemFrame *p_frame, int p_line, const V
 	Vector2 off;
 
 	int char_pos = -1;
-	Line &l = p_frame->lines.write[p_line];
+	Line &l = p_frame->lines[p_line];
+	MutexLock lock(l.text_buf->get_mutex());
+
 	bool rtl = (l.text_buf->get_direction() == TextServer::DIRECTION_RTL);
 	bool lrtl = is_layout_rtl();
 
@@ -1420,14 +1414,14 @@ float RichTextLabel::_find_click_in_line(ItemFrame *p_frame, int p_line, const V
 										}
 									}
 									if (crect.has_point(p_click)) {
-										for (int j = 0; j < frame->lines.size(); j++) {
+										for (int j = 0; j < (int)frame->lines.size(); j++) {
 											_find_click_in_line(frame, j, rect.position + Vector2(0, frame->lines[j].offset.y), rect.size.x, p_click, &table_click_frame, &table_click_line, &table_click_item, &table_click_char, true);
 											if (table_click_frame && table_click_item) {
 												// Save cell detected cell hit data.
 												table_range = Vector2i(INT32_MAX, 0);
 												for (Item *F : table->subitems) {
 													ItemFrame *sub_frame = static_cast<ItemFrame *>(F);
-													for (int k = 0; k < sub_frame->lines.size(); k++) {
+													for (int k = 0; k < (int)sub_frame->lines.size(); k++) {
 														table_range.x = MIN(table_range.x, sub_frame->lines[k].char_offset);
 														table_range.y = MAX(table_range.y, sub_frame->lines[k].char_offset + sub_frame->lines[k].char_count);
 													}
@@ -1484,7 +1478,7 @@ float RichTextLabel::_find_click_in_line(ItemFrame *p_frame, int p_line, const V
 		// Find item.
 		if (r_click_item != nullptr) {
 			Item *it = p_frame->lines[p_line].from;
-			Item *it_to = (p_line + 1 < p_frame->lines.size()) ? p_frame->lines[p_line + 1].from : nullptr;
+			Item *it_to = (p_line + 1 < (int)p_frame->lines.size()) ? p_frame->lines[p_line + 1].from : nullptr;
 			if (char_pos == p_frame->lines[p_line].char_count) {
 				// Selection after the end of line, select last item.
 				if (it_to != nullptr) {
@@ -1532,28 +1526,6 @@ void RichTextLabel::_scroll_changed(double) {
 	update();
 }
 
-void RichTextLabel::_update_scroll() {
-	int total_height = get_content_height();
-
-	bool exceeds = total_height > get_size().height && scroll_active;
-
-	if (exceeds != scroll_visible) {
-		if (exceeds) {
-			scroll_visible = true;
-			scroll_w = vscroll->get_combined_minimum_size().width;
-			vscroll->show();
-			vscroll->set_anchor_and_offset(SIDE_LEFT, ANCHOR_END, -scroll_w);
-		} else {
-			scroll_visible = false;
-			scroll_w = 0;
-			vscroll->hide();
-		}
-
-		main->first_resized_line = 0; //invalidate ALL
-		_validate_line_caches(main);
-	}
-}
-
 void RichTextLabel::_update_fx(RichTextLabel::ItemFrame *p_frame, double p_delta_time) {
 	Item *it = p_frame;
 	while (it) {
@@ -1588,6 +1560,22 @@ void RichTextLabel::_update_fx(RichTextLabel::ItemFrame *p_frame, double p_delta
 	}
 }
 
+int RichTextLabel::_find_first_line(int p_from, int p_to, int p_vofs) const {
+	int l = p_from;
+	int r = p_to;
+	while (l < r) {
+		int m = Math::floor(double(l + r) / 2.0);
+		MutexLock lock(main->lines[m].text_buf->get_mutex());
+		int ofs = main->lines[m].offset.y + main->lines[m].text_buf->get_size().y + main->lines[m].text_buf->get_line_count() * get_theme_constant(SNAME("line_separation"));
+		if (ofs < p_vofs) {
+			l = m + 1;
+		} else {
+			r = m;
+		}
+	}
+	return l;
+}
+
 void RichTextLabel::_notification(int p_what) {
 	switch (p_what) {
 		case NOTIFICATION_MOUSE_EXIT: {
@@ -1600,38 +1588,45 @@ void RichTextLabel::_notification(int p_what) {
 		} break;
 
 		case NOTIFICATION_RESIZED: {
-			main->first_resized_line = 0; //invalidate ALL
+			_stop_thread();
+			main->first_resized_line.store(0); //invalidate ALL
 			update();
 		} break;
 
 		case NOTIFICATION_THEME_CHANGED: {
-			main->first_invalid_font_line = 0; //invalidate ALL
+			_stop_thread();
+			main->first_invalid_font_line.store(0); //invalidate ALL
 			update();
 		} break;
 
 		case NOTIFICATION_ENTER_TREE: {
+			_stop_thread();
 			if (!text.is_empty()) {
 				set_text(text);
 			}
 
-			main->first_invalid_line = 0; //invalidate ALL
+			main->first_invalid_line.store(0); //invalidate ALL
 			update();
 		} break;
 
+		case NOTIFICATION_EXIT_TREE: {
+			_stop_thread();
+		} break;
+
 		case NOTIFICATION_LAYOUT_DIRECTION_CHANGED:
 		case NOTIFICATION_TRANSLATION_CHANGED: {
-			main->first_invalid_line = 0; //invalidate ALL
+			_stop_thread();
+			main->first_invalid_line.store(0); //invalidate ALL
 			update();
 		} break;
 
-		case NOTIFICATION_DRAW: {
-			_validate_line_caches(main);
-			_update_scroll();
+		case NOTIFICATION_INTERNAL_PHYSICS_PROCESS: {
+			update();
+		} break;
 
+		case NOTIFICATION_DRAW: {
 			RID ci = get_canvas_item();
-
 			Size2 size = get_size();
-			Rect2 text_rect = _get_text_rect();
 
 			draw_style_box(get_theme_stylebox(SNAME("normal")), Rect2(Point2(), size));
 
@@ -1641,22 +1636,42 @@ void RichTextLabel::_notification(int p_what) {
 				RenderingServer::get_singleton()->canvas_item_add_clip_ignore(ci, false);
 			}
 
+			// Start text shaping.
+			if (_validate_line_caches()) {
+				set_physics_process_internal(false); // Disable auto refresh, if text is fully processed.
+			} else {
+				// Draw loading progress bar.
+				if ((progress_delay > 0) && (OS::get_singleton()->get_ticks_msec() - loading_started >= (uint64_t)progress_delay)) {
+					Ref<StyleBox> bg = get_theme_stylebox(SNAME("bg"), SNAME("ProgressBar"));
+					Ref<StyleBox> fg = get_theme_stylebox(SNAME("fg"), SNAME("ProgressBar"));
+					Ref<StyleBox> style = get_theme_stylebox(SNAME("normal"));
+
+					Vector2 p_size = Vector2(size.width - (style->get_offset().x + vscroll->get_combined_minimum_size().width) * 2, vscroll->get_combined_minimum_size().width);
+					Vector2 p_pos = Vector2(style->get_offset().x, size.height - style->get_offset().y - vscroll->get_combined_minimum_size().width);
+
+					draw_style_box(bg, Rect2(p_pos, p_size));
+
+					bool right_to_left = is_layout_rtl();
+					double r = loaded.load();
+					int mp = fg->get_minimum_size().width;
+					int p = round(r * (p_size.width - mp));
+					if (right_to_left) {
+						int p_remaining = round((1.0 - r) * (p_size.width - mp));
+						draw_style_box(fg, Rect2(p_pos + Point2(p_remaining, 0), Size2(p + fg->get_minimum_size().width, p_size.height)));
+					} else {
+						draw_style_box(fg, Rect2(p_pos, Size2(p + fg->get_minimum_size().width, p_size.height)));
+					}
+				}
+			}
+
+			// Draw main text.
+			Rect2 text_rect = _get_text_rect();
 			float vofs = vscroll->get_value();
 
 			// Search for the first line.
-			int from_line = 0;
-
-			//TODO, change to binary search ?
-			while (from_line < main->lines.size()) {
-				if (main->lines[from_line].offset.y + main->lines[from_line].text_buf->get_size().y + main->lines[from_line].text_buf->get_line_count() * get_theme_constant(SNAME("line_separation")) >= vofs) {
-					break;
-				}
-				from_line++;
-			}
+			int to_line = main->first_invalid_line.load();
+			int from_line = _find_first_line(0, to_line, vofs);
 
-			if (from_line >= main->lines.size()) {
-				break; //nothing to draw
-			}
 			Ref<Font> base_font = get_theme_font(SNAME("normal_font"));
 			Color base_color = get_theme_color(SNAME("default_color"));
 			Color outline_color = get_theme_color(SNAME("font_outline_color"));
@@ -1671,7 +1686,9 @@ void RichTextLabel::_notification(int p_what) {
 			// New cache draw.
 			Point2 ofs = text_rect.get_position() + Vector2(0, main->lines[from_line].offset.y - vofs);
 			int processed_glyphs = 0;
-			while (ofs.y < size.height && from_line < main->lines.size()) {
+			while (ofs.y < size.height && from_line < to_line) {
+				MutexLock lock(main->lines[from_line].text_buf->get_mutex());
+
 				visible_paragraph_count++;
 				visible_line_count += _draw_line(main, from_line, ofs, text_rect.size.x, base_color, outline_size, outline_color, font_shadow_color, shadow_outline_size, shadow_ofs, processed_glyphs);
 				ofs.y += main->lines[from_line].text_buf->get_size().y + main->lines[from_line].text_buf->get_line_count() * get_theme_constant(SNAME("line_separation"));
@@ -1681,6 +1698,9 @@ void RichTextLabel::_notification(int p_what) {
 
 		case NOTIFICATION_INTERNAL_PROCESS: {
 			if (is_visible_in_tree()) {
+				if (!is_ready()) {
+					return;
+				}
 				double dt = get_process_delta_time();
 				_update_fx(main, dt);
 				update();
@@ -1708,18 +1728,6 @@ Control::CursorShape RichTextLabel::get_cursor_shape(const Point2 &p_pos) const
 		return CURSOR_IBEAM;
 	}
 
-	if (main->first_invalid_line < main->lines.size()) {
-		return get_default_cursor_shape(); //invalid
-	}
-
-	if (main->first_invalid_font_line < main->lines.size()) {
-		return get_default_cursor_shape(); //invalid
-	}
-
-	if (main->first_resized_line < main->lines.size()) {
-		return get_default_cursor_shape(); //invalid
-	}
-
 	Item *item = nullptr;
 	bool outside = true;
 	const_cast<RichTextLabel *>(this)->_find_click(main, p_pos, nullptr, nullptr, &item, nullptr, &outside);
@@ -1727,7 +1735,6 @@ Control::CursorShape RichTextLabel::get_cursor_shape(const Point2 &p_pos) const
 	if (item && !outside && const_cast<RichTextLabel *>(this)->_find_meta(item, nullptr)) {
 		return CURSOR_POINTING_HAND;
 	}
-
 	return get_default_cursor_shape();
 }
 
@@ -1737,16 +1744,6 @@ void RichTextLabel::gui_input(const Ref<InputEvent> &p_event) {
 	Ref<InputEventMouseButton> b = p_event;
 
 	if (b.is_valid()) {
-		if (main->first_invalid_line < main->lines.size()) {
-			return;
-		}
-		if (main->first_invalid_font_line < main->lines.size()) {
-			return;
-		}
-		if (main->first_resized_line < main->lines.size()) {
-			return;
-		}
-
 		if (b->get_button_index() == MouseButton::LEFT) {
 			if (b->is_pressed() && !b->is_double_click()) {
 				scroll_updated = false;
@@ -1800,6 +1797,7 @@ void RichTextLabel::gui_input(const Ref<InputEvent> &p_event) {
 
 				if (c_frame) {
 					const Line &l = c_frame->lines[c_line];
+					MutexLock lock(l.text_buf->get_mutex());
 					PackedInt32Array words = TS->shaped_text_get_word_breaks(l.text_buf->get_rid());
 					for (int i = 0; i < words.size(); i = i + 2) {
 						if (c_index >= words[i] && c_index < words[i + 1]) {
@@ -1945,18 +1943,7 @@ void RichTextLabel::gui_input(const Ref<InputEvent> &p_event) {
 	}
 
 	Ref<InputEventMouseMotion> m = p_event;
-
 	if (m.is_valid()) {
-		if (main->first_invalid_line < main->lines.size()) {
-			return;
-		}
-		if (main->first_invalid_font_line < main->lines.size()) {
-			return;
-		}
-		if (main->first_resized_line < main->lines.size()) {
-			return;
-		}
-
 		ItemFrame *c_frame = nullptr;
 		int c_line = 0;
 		Item *c_item = nullptr;
@@ -2434,93 +2421,215 @@ bool RichTextLabel::_find_layout_subitem(Item *from, Item *to) {
 	return false;
 }
 
-void RichTextLabel::_validate_line_caches(ItemFrame *p_frame) {
-	if (p_frame->first_invalid_line == p_frame->lines.size()) {
+void RichTextLabel::_thread_function(void *self) {
+	RichTextLabel *rtl = reinterpret_cast<RichTextLabel *>(self);
+	rtl->_process_line_caches();
+	rtl->updating.store(false);
+	rtl->call_deferred(SNAME("update"));
+}
+
+void RichTextLabel::_stop_thread() {
+	if (threaded) {
+		stop_thread.store(true);
+		thread.wait_to_finish();
+	}
+}
+
+bool RichTextLabel::is_ready() const {
+	if (updating.load()) {
+		return false;
+	}
+	return (main->first_invalid_line.load() == (int)main->lines.size() && main->first_resized_line.load() == (int)main->lines.size() && main->first_invalid_font_line.load() == (int)main->lines.size());
+}
+
+void RichTextLabel::set_threaded(bool p_threaded) {
+	if (threaded != p_threaded) {
+		_stop_thread();
+		threaded = p_threaded;
+		update();
+	}
+}
+
+bool RichTextLabel::is_threaded() const {
+	return threaded;
+}
+
+void RichTextLabel::set_progress_bar_delay(int p_delay_ms) {
+	progress_delay = p_delay_ms;
+}
+
+int RichTextLabel::get_progress_bar_delay() const {
+	return progress_delay;
+}
+
+bool RichTextLabel::_validate_line_caches() {
+	if (updating.load()) {
+		return false;
+	}
+	if (main->first_invalid_line.load() == (int)main->lines.size()) {
+		MutexLock data_lock(data_mutex);
+		Rect2 text_rect = _get_text_rect();
+
 		Ref<Font> base_font = get_theme_font(SNAME("normal_font"));
 		int base_font_size = get_theme_font_size(SNAME("normal_font_size"));
+		int ctrl_height = get_size().height;
 
 		// Update fonts.
-		if (p_frame->first_invalid_font_line != p_frame->lines.size()) {
-			for (int i = p_frame->first_invalid_font_line; i < p_frame->lines.size(); i++) {
-				_update_line_font(p_frame, i, base_font, base_font_size);
+		if (main->first_invalid_font_line.load() != (int)main->lines.size()) {
+			for (int i = main->first_invalid_font_line.load(); i < (int)main->lines.size(); i++) {
+				_update_line_font(main, i, base_font, base_font_size);
 			}
-			p_frame->first_resized_line = p_frame->first_invalid_font_line;
-			p_frame->first_invalid_font_line = p_frame->lines.size();
+			main->first_resized_line.store(main->first_invalid_font_line.load());
+			main->first_invalid_font_line.store(main->lines.size());
 		}
 
-		if (p_frame->first_resized_line == p_frame->lines.size()) {
-			return;
+		if (main->first_resized_line.load() == (int)main->lines.size()) {
+			return true;
 		}
 
 		// Resize lines without reshaping.
-		Rect2 text_rect = _get_text_rect();
+		int fi = main->first_resized_line.load();
+
+		float total_height = 0;
+		for (int i = fi; i < (int)main->lines.size(); i++) {
+			total_height = _resize_line(main, i, base_font, base_font_size, text_rect.get_size().width - scroll_w, total_height);
+
+			updating_scroll = true;
+			bool exceeds = total_height > ctrl_height && scroll_active;
+			if (exceeds != scroll_visible) {
+				if (exceeds) {
+					scroll_visible = true;
+					scroll_w = vscroll->get_combined_minimum_size().width;
+					vscroll->show();
+					vscroll->set_anchor_and_offset(SIDE_LEFT, ANCHOR_END, -scroll_w);
+				} else {
+					scroll_visible = false;
+					scroll_w = 0;
+					vscroll->hide();
+				}
 
-		for (int i = p_frame->first_resized_line; i < p_frame->lines.size(); i++) {
-			_resize_line(p_frame, i, base_font, base_font_size, text_rect.get_size().width - scroll_w);
-		}
+				main->first_resized_line.store(0);
 
-		int total_height = 0;
-		if (p_frame->lines.size()) {
-			total_height = p_frame->lines[p_frame->lines.size() - 1].offset.y + p_frame->lines[p_frame->lines.size() - 1].text_buf->get_size().y + p_frame->lines[p_frame->lines.size() - 1].text_buf->get_line_count() * get_theme_constant(SNAME("line_separation"));
-		}
+				total_height = 0;
+				for (int j = 0; j <= i; j++) {
+					total_height = _resize_line(main, j, base_font, base_font_size, text_rect.get_size().width - scroll_w, total_height);
+
+					main->first_resized_line.store(j);
+				}
+			}
 
-		p_frame->first_resized_line = p_frame->lines.size();
+			vscroll->set_max(total_height);
+			vscroll->set_page(text_rect.size.height);
+			if (scroll_follow && scroll_following) {
+				vscroll->set_value(total_height);
+			}
+			updating_scroll = false;
 
-		updating_scroll = true;
-		vscroll->set_max(total_height);
-		vscroll->set_page(text_rect.size.height);
-		if (scroll_follow && scroll_following) {
-			vscroll->set_value(total_height);
+			main->first_resized_line.store(i);
 		}
-		updating_scroll = false;
+
+		main->first_resized_line.store(main->lines.size());
 
 		if (fit_content_height) {
 			update_minimum_size();
 		}
-		return;
+		return true;
 	}
+	stop_thread.store(false);
+	if (threaded) {
+		updating.store(true);
+		loaded.store(true);
+		thread.start(RichTextLabel::_thread_function, reinterpret_cast<void *>(this));
+		loading_started = OS::get_singleton()->get_ticks_msec();
+		set_physics_process_internal(true);
+		return false;
+	} else {
+		_process_line_caches();
+		update();
+		return true;
+	}
+}
 
+void RichTextLabel::_process_line_caches() {
 	// Shape invalid lines.
+	MutexLock data_lock(data_mutex);
 	Rect2 text_rect = _get_text_rect();
 
 	Ref<Font> base_font = get_theme_font(SNAME("normal_font"));
 	int base_font_size = get_theme_font_size(SNAME("normal_font_size"));
+	int ctrl_height = get_size().height;
+	int fi = main->first_invalid_line.load();
+	int total_chars = (fi == 0) ? 0 : (main->lines[fi].char_offset + main->lines[fi].char_count);
 
-	int total_chars = (p_frame->first_invalid_line == 0) ? 0 : (p_frame->lines[p_frame->first_invalid_line].char_offset + p_frame->lines[p_frame->first_invalid_line].char_count);
-	for (int i = p_frame->first_invalid_line; i < p_frame->lines.size(); i++) {
-		_shape_line(p_frame, i, base_font, base_font_size, text_rect.get_size().width - scroll_w, &total_chars);
-	}
+	float total_height = 0;
+	for (int i = fi; i < (int)main->lines.size(); i++) {
+		total_height = _shape_line(main, i, base_font, base_font_size, text_rect.get_size().width - scroll_w, total_height, &total_chars);
 
-	int total_height = 0;
-	if (p_frame->lines.size()) {
-		total_height = p_frame->lines[p_frame->lines.size() - 1].offset.y + p_frame->lines[p_frame->lines.size() - 1].text_buf->get_size().y + p_frame->lines[p_frame->lines.size() - 1].text_buf->get_line_count() * get_theme_constant(SNAME("line_separation"));
-	}
+		updating_scroll = true;
+		bool exceeds = total_height > ctrl_height && scroll_active;
+		if (exceeds != scroll_visible) {
+			if (exceeds) {
+				scroll_visible = true;
+				scroll_w = vscroll->get_combined_minimum_size().width;
+				vscroll->show();
+				vscroll->set_anchor_and_offset(SIDE_LEFT, ANCHOR_END, -scroll_w);
+			} else {
+				scroll_visible = false;
+				scroll_w = 0;
+				vscroll->hide();
+			}
 
-	p_frame->first_invalid_line = p_frame->lines.size();
-	p_frame->first_resized_line = p_frame->lines.size();
-	p_frame->first_invalid_font_line = p_frame->lines.size();
+			main->first_invalid_line.store(0);
+			main->first_resized_line.store(0);
+			main->first_invalid_font_line.store(0);
 
-	updating_scroll = true;
-	vscroll->set_max(total_height);
-	vscroll->set_page(text_rect.size.height);
-	if (scroll_follow && scroll_following) {
-		vscroll->set_value(total_height);
+			total_height = 0;
+			for (int j = 0; j <= i; j++) {
+				total_height = _resize_line(main, j, base_font, base_font_size, text_rect.get_size().width - scroll_w, total_height);
+
+				main->first_invalid_line.store(j);
+				main->first_resized_line.store(j);
+				main->first_invalid_font_line.store(j);
+			}
+		}
+
+		vscroll->set_max(total_height);
+		vscroll->set_page(text_rect.size.height);
+		if (scroll_follow && scroll_following) {
+			vscroll->set_value(total_height);
+		}
+		updating_scroll = false;
+
+		main->first_invalid_line.store(i);
+		main->first_resized_line.store(i);
+		main->first_invalid_font_line.store(i);
+
+		if (stop_thread.load()) {
+			return;
+		}
+		loaded.store(double(i) / double(main->lines.size()));
 	}
-	updating_scroll = false;
+
+	main->first_invalid_line.store(main->lines.size());
+	main->first_resized_line.store(main->lines.size());
+	main->first_invalid_font_line.store(main->lines.size());
 
 	if (fit_content_height) {
 		update_minimum_size();
 	}
+	emit_signal(SNAME("finished"));
 }
 
 void RichTextLabel::_invalidate_current_line(ItemFrame *p_frame) {
-	if (p_frame->lines.size() - 1 <= p_frame->first_invalid_line) {
-		p_frame->first_invalid_line = p_frame->lines.size() - 1;
-		update();
+	if ((int)p_frame->lines.size() - 1 <= p_frame->first_invalid_line) {
+		p_frame->first_invalid_line = (int)p_frame->lines.size() - 1;
 	}
 }
 
 void RichTextLabel::add_text(const String &p_text) {
+	_stop_thread();
+	MutexLock data_lock(data_mutex);
+
 	if (current->type == ITEM_TABLE) {
 		return; //can't add anything here
 	}
@@ -2564,13 +2673,14 @@ void RichTextLabel::add_text(const String &p_text) {
 			_add_item(item, false);
 			current_frame->lines.resize(current_frame->lines.size() + 1);
 			if (item->type != ITEM_NEWLINE) {
-				current_frame->lines.write[current_frame->lines.size() - 1].from = item;
+				current_frame->lines[current_frame->lines.size() - 1].from = item;
 			}
 			_invalidate_current_line(current_frame);
 		}
 
 		pos = end + 1;
 	}
+	update();
 }
 
 void RichTextLabel::_add_item(Item *p_item, bool p_enter, bool p_ensure_newline) {
@@ -2599,7 +2709,7 @@ void RichTextLabel::_add_item(Item *p_item, bool p_enter, bool p_ensure_newline)
 	}
 
 	if (current_frame->lines[current_frame->lines.size() - 1].from == nullptr) {
-		current_frame->lines.write[current_frame->lines.size() - 1].from = p_item;
+		current_frame->lines[current_frame->lines.size() - 1].from = p_item;
 	}
 	p_item->line = current_frame->lines.size() - 1;
 
@@ -2608,6 +2718,7 @@ void RichTextLabel::_add_item(Item *p_item, bool p_enter, bool p_ensure_newline)
 	if (fixed_width != -1) {
 		update_minimum_size();
 	}
+	update();
 }
 
 void RichTextLabel::_remove_item(Item *p_item, const int p_line, const int p_subitem_line) {
@@ -2635,6 +2746,9 @@ void RichTextLabel::_remove_item(Item *p_item, const int p_line, const int p_sub
 }
 
 void RichTextLabel::add_image(const Ref<Texture2D> &p_image, const int p_width, const int p_height, const Color &p_color, InlineAlignment p_alignment) {
+	_stop_thread();
+	MutexLock data_lock(data_mutex);
+
 	if (current->type == ITEM_TABLE) {
 		return;
 	}
@@ -2674,6 +2788,9 @@ void RichTextLabel::add_image(const Ref<Texture2D> &p_image, const int p_width,
 }
 
 void RichTextLabel::add_newline() {
+	_stop_thread();
+	MutexLock data_lock(data_mutex);
+
 	if (current->type == ITEM_TABLE) {
 		return;
 	}
@@ -2682,10 +2799,14 @@ void RichTextLabel::add_newline() {
 	_add_item(item, false);
 	current_frame->lines.resize(current_frame->lines.size() + 1);
 	_invalidate_current_line(current_frame);
+	update();
 }
 
 bool RichTextLabel::remove_line(const int p_line) {
-	if (p_line >= current_frame->lines.size() || p_line < 0) {
+	_stop_thread();
+	MutexLock data_lock(data_mutex);
+
+	if (p_line >= (int)current_frame->lines.size() || p_line < 0) {
 		return false;
 	}
 
@@ -2713,16 +2834,19 @@ bool RichTextLabel::remove_line(const int p_line) {
 	}
 
 	if (p_line == 0 && current->subitems.size() > 0) {
-		main->lines.write[0].from = main;
+		main->lines[0].from = main;
 	}
 
-	main->first_invalid_line = 0; // p_line ???
+	main->first_invalid_line.store(0);
 	update();
 
 	return true;
 }
 
 void RichTextLabel::push_dropcap(const String &p_string, const Ref<Font> &p_font, int p_size, const Rect2 &p_dropcap_margins, const Color &p_color, int p_ol_size, const Color &p_ol_color) {
+	_stop_thread();
+	MutexLock data_lock(data_mutex);
+
 	ERR_FAIL_COND(current->type == ITEM_TABLE);
 	ERR_FAIL_COND(p_string.is_empty());
 	ERR_FAIL_COND(p_font.is_null());
@@ -2741,6 +2865,9 @@ void RichTextLabel::push_dropcap(const String &p_string, const Ref<Font> &p_font
 }
 
 void RichTextLabel::push_font(const Ref<Font> &p_font) {
+	_stop_thread();
+	MutexLock data_lock(data_mutex);
+
 	ERR_FAIL_COND(current->type == ITEM_TABLE);
 	ERR_FAIL_COND(p_font.is_null());
 	ItemFont *item = memnew(ItemFont);
@@ -2785,6 +2912,9 @@ void RichTextLabel::push_mono() {
 }
 
 void RichTextLabel::push_font_size(int p_font_size) {
+	_stop_thread();
+	MutexLock data_lock(data_mutex);
+
 	ERR_FAIL_COND(current->type == ITEM_TABLE);
 	ItemFontSize *item = memnew(ItemFontSize);
 
@@ -2793,6 +2923,9 @@ void RichTextLabel::push_font_size(int p_font_size) {
 }
 
 void RichTextLabel::push_font_features(const Dictionary &p_features) {
+	_stop_thread();
+	MutexLock data_lock(data_mutex);
+
 	ERR_FAIL_COND(current->type == ITEM_TABLE);
 	ItemFontFeatures *item = memnew(ItemFontFeatures);
 
@@ -2801,6 +2934,9 @@ void RichTextLabel::push_font_features(const Dictionary &p_features) {
 }
 
 void RichTextLabel::push_outline_size(int p_font_size) {
+	_stop_thread();
+	MutexLock data_lock(data_mutex);
+
 	ERR_FAIL_COND(current->type == ITEM_TABLE);
 	ItemOutlineSize *item = memnew(ItemOutlineSize);
 
@@ -2809,6 +2945,9 @@ void RichTextLabel::push_outline_size(int p_font_size) {
 }
 
 void RichTextLabel::push_color(const Color &p_color) {
+	_stop_thread();
+	MutexLock data_lock(data_mutex);
+
 	ERR_FAIL_COND(current->type == ITEM_TABLE);
 	ItemColor *item = memnew(ItemColor);
 
@@ -2817,6 +2956,9 @@ void RichTextLabel::push_color(const Color &p_color) {
 }
 
 void RichTextLabel::push_outline_color(const Color &p_color) {
+	_stop_thread();
+	MutexLock data_lock(data_mutex);
+
 	ERR_FAIL_COND(current->type == ITEM_TABLE);
 	ItemOutlineColor *item = memnew(ItemOutlineColor);
 
@@ -2825,6 +2967,9 @@ void RichTextLabel::push_outline_color(const Color &p_color) {
 }
 
 void RichTextLabel::push_underline() {
+	_stop_thread();
+	MutexLock data_lock(data_mutex);
+
 	ERR_FAIL_COND(current->type == ITEM_TABLE);
 	ItemUnderline *item = memnew(ItemUnderline);
 
@@ -2832,6 +2977,9 @@ void RichTextLabel::push_underline() {
 }
 
 void RichTextLabel::push_strikethrough() {
+	_stop_thread();
+	MutexLock data_lock(data_mutex);
+
 	ERR_FAIL_COND(current->type == ITEM_TABLE);
 	ItemStrikethrough *item = memnew(ItemStrikethrough);
 
@@ -2839,6 +2987,9 @@ void RichTextLabel::push_strikethrough() {
 }
 
 void RichTextLabel::push_paragraph(HorizontalAlignment p_alignment, Control::TextDirection p_direction, const String &p_language, TextServer::StructuredTextParser p_st_parser) {
+	_stop_thread();
+	MutexLock data_lock(data_mutex);
+
 	ERR_FAIL_COND(current->type == ITEM_TABLE);
 
 	ItemParagraph *item = memnew(ItemParagraph);
@@ -2850,6 +3001,9 @@ void RichTextLabel::push_paragraph(HorizontalAlignment p_alignment, Control::Tex
 }
 
 void RichTextLabel::push_indent(int p_level) {
+	_stop_thread();
+	MutexLock data_lock(data_mutex);
+
 	ERR_FAIL_COND(current->type == ITEM_TABLE);
 	ERR_FAIL_COND(p_level < 0);
 
@@ -2859,6 +3013,9 @@ void RichTextLabel::push_indent(int p_level) {
 }
 
 void RichTextLabel::push_list(int p_level, ListType p_list, bool p_capitalize) {
+	_stop_thread();
+	MutexLock data_lock(data_mutex);
+
 	ERR_FAIL_COND(current->type == ITEM_TABLE);
 	ERR_FAIL_COND(p_level < 0);
 
@@ -2871,6 +3028,9 @@ void RichTextLabel::push_list(int p_level, ListType p_list, bool p_capitalize) {
 }
 
 void RichTextLabel::push_meta(const Variant &p_meta) {
+	_stop_thread();
+	MutexLock data_lock(data_mutex);
+
 	ERR_FAIL_COND(current->type == ITEM_TABLE);
 	ItemMeta *item = memnew(ItemMeta);
 
@@ -2879,6 +3039,9 @@ void RichTextLabel::push_meta(const Variant &p_meta) {
 }
 
 void RichTextLabel::push_hint(const String &p_string) {
+	_stop_thread();
+	MutexLock data_lock(data_mutex);
+
 	ERR_FAIL_COND(current->type == ITEM_TABLE);
 	ItemHint *item = memnew(ItemHint);
 
@@ -2887,20 +3050,26 @@ void RichTextLabel::push_hint(const String &p_string) {
 }
 
 void RichTextLabel::push_table(int p_columns, InlineAlignment p_alignment) {
+	_stop_thread();
+	MutexLock data_lock(data_mutex);
+
 	ERR_FAIL_COND(p_columns < 1);
 	ItemTable *item = memnew(ItemTable);
 
 	item->columns.resize(p_columns);
 	item->total_width = 0;
 	item->inline_align = p_alignment;
-	for (int i = 0; i < item->columns.size(); i++) {
-		item->columns.write[i].expand = false;
-		item->columns.write[i].expand_ratio = 1;
+	for (int i = 0; i < (int)item->columns.size(); i++) {
+		item->columns[i].expand = false;
+		item->columns[i].expand_ratio = 1;
 	}
 	_add_item(item, true, false);
 }
 
 void RichTextLabel::push_fade(int p_start_index, int p_length) {
+	_stop_thread();
+	MutexLock data_lock(data_mutex);
+
 	ItemFade *item = memnew(ItemFade);
 	item->starting_index = p_start_index;
 	item->length = p_length;
@@ -2908,6 +3077,9 @@ void RichTextLabel::push_fade(int p_start_index, int p_length) {
 }
 
 void RichTextLabel::push_shake(int p_strength = 10, float p_rate = 24.0f) {
+	_stop_thread();
+	MutexLock data_lock(data_mutex);
+
 	ItemShake *item = memnew(ItemShake);
 	item->strength = p_strength;
 	item->rate = p_rate;
@@ -2915,6 +3087,9 @@ void RichTextLabel::push_shake(int p_strength = 10, float p_rate = 24.0f) {
 }
 
 void RichTextLabel::push_wave(float p_frequency = 1.0f, float p_amplitude = 10.0f) {
+	_stop_thread();
+	MutexLock data_lock(data_mutex);
+
 	ItemWave *item = memnew(ItemWave);
 	item->frequency = p_frequency;
 	item->amplitude = p_amplitude;
@@ -2922,6 +3097,9 @@ void RichTextLabel::push_wave(float p_frequency = 1.0f, float p_amplitude = 10.0
 }
 
 void RichTextLabel::push_tornado(float p_frequency = 1.0f, float p_radius = 10.0f) {
+	_stop_thread();
+	MutexLock data_lock(data_mutex);
+
 	ItemTornado *item = memnew(ItemTornado);
 	item->frequency = p_frequency;
 	item->radius = p_radius;
@@ -2929,6 +3107,9 @@ void RichTextLabel::push_tornado(float p_frequency = 1.0f, float p_radius = 10.0
 }
 
 void RichTextLabel::push_rainbow(float p_saturation, float p_value, float p_frequency) {
+	_stop_thread();
+	MutexLock data_lock(data_mutex);
+
 	ItemRainbow *item = memnew(ItemRainbow);
 	item->frequency = p_frequency;
 	item->saturation = p_saturation;
@@ -2937,6 +3118,9 @@ void RichTextLabel::push_rainbow(float p_saturation, float p_value, float p_freq
 }
 
 void RichTextLabel::push_bgcolor(const Color &p_color) {
+	_stop_thread();
+	MutexLock data_lock(data_mutex);
+
 	ERR_FAIL_COND(current->type == ITEM_TABLE);
 	ItemBGColor *item = memnew(ItemBGColor);
 
@@ -2945,6 +3129,9 @@ void RichTextLabel::push_bgcolor(const Color &p_color) {
 }
 
 void RichTextLabel::push_fgcolor(const Color &p_color) {
+	_stop_thread();
+	MutexLock data_lock(data_mutex);
+
 	ERR_FAIL_COND(current->type == ITEM_TABLE);
 	ItemFGColor *item = memnew(ItemFGColor);
 
@@ -2953,6 +3140,9 @@ void RichTextLabel::push_fgcolor(const Color &p_color) {
 }
 
 void RichTextLabel::push_customfx(Ref<RichTextEffect> p_custom_effect, Dictionary p_environment) {
+	_stop_thread();
+	MutexLock data_lock(data_mutex);
+
 	ItemCustomFX *item = memnew(ItemCustomFX);
 	item->custom_effect = p_custom_effect;
 	item->char_fx_transform->environment = p_environment;
@@ -2960,15 +3150,23 @@ void RichTextLabel::push_customfx(Ref<RichTextEffect> p_custom_effect, Dictionar
 }
 
 void RichTextLabel::set_table_column_expand(int p_column, bool p_expand, int p_ratio) {
+	_stop_thread();
+	MutexLock data_lock(data_mutex);
+
 	ERR_FAIL_COND(current->type != ITEM_TABLE);
+
 	ItemTable *table = static_cast<ItemTable *>(current);
-	ERR_FAIL_INDEX(p_column, table->columns.size());
-	table->columns.write[p_column].expand = p_expand;
-	table->columns.write[p_column].expand_ratio = p_ratio;
+	ERR_FAIL_INDEX(p_column, (int)table->columns.size());
+	table->columns[p_column].expand = p_expand;
+	table->columns[p_column].expand_ratio = p_ratio;
 }
 
 void RichTextLabel::set_cell_row_background_color(const Color &p_odd_row_bg, const Color &p_even_row_bg) {
+	_stop_thread();
+	MutexLock data_lock(data_mutex);
+
 	ERR_FAIL_COND(current->type != ITEM_FRAME);
+
 	ItemFrame *cell = static_cast<ItemFrame *>(current);
 	ERR_FAIL_COND(!cell->cell);
 	cell->odd_row_bg = p_odd_row_bg;
@@ -2976,14 +3174,22 @@ void RichTextLabel::set_cell_row_background_color(const Color &p_odd_row_bg, con
 }
 
 void RichTextLabel::set_cell_border_color(const Color &p_color) {
+	_stop_thread();
+	MutexLock data_lock(data_mutex);
+
 	ERR_FAIL_COND(current->type != ITEM_FRAME);
+
 	ItemFrame *cell = static_cast<ItemFrame *>(current);
 	ERR_FAIL_COND(!cell->cell);
 	cell->border = p_color;
 }
 
 void RichTextLabel::set_cell_size_override(const Size2 &p_min_size, const Size2 &p_max_size) {
+	_stop_thread();
+	MutexLock data_lock(data_mutex);
+
 	ERR_FAIL_COND(current->type != ITEM_FRAME);
+
 	ItemFrame *cell = static_cast<ItemFrame *>(current);
 	ERR_FAIL_COND(!cell->cell);
 	cell->min_size_over = p_min_size;
@@ -2991,13 +3197,20 @@ void RichTextLabel::set_cell_size_override(const Size2 &p_min_size, const Size2
 }
 
 void RichTextLabel::set_cell_padding(const Rect2 &p_padding) {
+	_stop_thread();
+	MutexLock data_lock(data_mutex);
+
 	ERR_FAIL_COND(current->type != ITEM_FRAME);
+
 	ItemFrame *cell = static_cast<ItemFrame *>(current);
 	ERR_FAIL_COND(!cell->cell);
 	cell->padding = p_padding;
 }
 
 void RichTextLabel::push_cell() {
+	_stop_thread();
+	MutexLock data_lock(data_mutex);
+
 	ERR_FAIL_COND(current->type != ITEM_TABLE);
 
 	ItemFrame *item = memnew(ItemFrame);
@@ -3006,20 +3219,23 @@ void RichTextLabel::push_cell() {
 	current_frame = item;
 	item->cell = true;
 	item->lines.resize(1);
-	item->lines.write[0].from = nullptr;
-	item->first_invalid_line = 0; // parent frame last line ???
+	item->lines[0].from = nullptr;
+	item->first_invalid_line.store(0); // parent frame last line ???
 }
 
 int RichTextLabel::get_current_table_column() const {
 	ERR_FAIL_COND_V(current->type != ITEM_TABLE, -1);
 
 	ItemTable *table = static_cast<ItemTable *>(current);
-
 	return table->subitems.size() % table->columns.size();
 }
 
 void RichTextLabel::pop() {
+	_stop_thread();
+	MutexLock data_lock(data_mutex);
+
 	ERR_FAIL_COND(!current->parent);
+
 	if (current->type == ITEM_FRAME) {
 		current_frame = static_cast<ItemFrame *>(current)->parent_frame;
 	}
@@ -3027,12 +3243,15 @@ void RichTextLabel::pop() {
 }
 
 void RichTextLabel::clear() {
+	_stop_thread();
+	MutexLock data_lock(data_mutex);
+
 	main->_clear_children();
 	current = main;
 	current_frame = main;
 	main->lines.clear();
 	main->lines.resize(1);
-	main->first_invalid_line = 0;
+	main->first_invalid_line.store(0);
 
 	selection.click_frame = nullptr;
 	selection.click_item = nullptr;
@@ -3050,8 +3269,10 @@ void RichTextLabel::clear() {
 }
 
 void RichTextLabel::set_tab_size(int p_spaces) {
+	_stop_thread();
+
 	tab_size = p_spaces;
-	main->first_resized_line = 0;
+	main->first_resized_line.store(0);
 	update();
 }
 
@@ -3131,6 +3352,9 @@ void RichTextLabel::parse_bbcode(const String &p_bbcode) {
 }
 
 void RichTextLabel::append_text(const String &p_bbcode) {
+	_stop_thread();
+	MutexLock data_lock(data_mutex);
+
 	int pos = 0;
 
 	List<String> tag_stack;
@@ -3871,9 +4095,13 @@ void RichTextLabel::append_text(const String &p_bbcode) {
 }
 
 void RichTextLabel::scroll_to_paragraph(int p_paragraph) {
-	ERR_FAIL_INDEX(p_paragraph, main->lines.size());
-	_validate_line_caches(main);
-	vscroll->set_value(main->lines[p_paragraph].offset.y);
+	if (p_paragraph <= 0) {
+		vscroll->set_value(0);
+	} else if (p_paragraph >= main->first_invalid_line.load()) {
+		vscroll->set_value(vscroll->get_max());
+	} else {
+		vscroll->set_value(main->lines[p_paragraph].offset.y);
+	}
 }
 
 int RichTextLabel::get_paragraph_count() const {
@@ -3888,10 +4116,14 @@ int RichTextLabel::get_visible_paragraph_count() const {
 }
 
 void RichTextLabel::scroll_to_line(int p_line) {
-	_validate_line_caches(main);
-
+	if (p_line <= 0) {
+		vscroll->set_value(0);
+		return;
+	}
 	int line_count = 0;
-	for (int i = 0; i < main->lines.size(); i++) {
+	int to_line = main->first_invalid_line.load();
+	for (int i = 0; i < to_line; i++) {
+		MutexLock lock(main->lines[i].text_buf->get_mutex());
 		if ((line_count <= p_line) && (line_count + main->lines[i].text_buf->get_line_count() >= p_line)) {
 			float line_offset = 0.f;
 			for (int j = 0; j < p_line - line_count; j++) {
@@ -3902,11 +4134,14 @@ void RichTextLabel::scroll_to_line(int p_line) {
 		}
 		line_count += main->lines[i].text_buf->get_line_count();
 	}
+	vscroll->set_value(vscroll->get_max());
 }
 
 float RichTextLabel::get_line_offset(int p_line) {
 	int line_count = 0;
-	for (int i = 0; i < main->lines.size(); i++) {
+	int to_line = main->first_invalid_line.load();
+	for (int i = 0; i < to_line; i++) {
+		MutexLock lock(main->lines[i].text_buf->get_mutex());
 		if ((line_count <= p_line) && (p_line <= line_count + main->lines[i].text_buf->get_line_count())) {
 			float line_offset = 0.f;
 			for (int j = 0; j < p_line - line_count; j++) {
@@ -3920,7 +4155,8 @@ float RichTextLabel::get_line_offset(int p_line) {
 }
 
 float RichTextLabel::get_paragraph_offset(int p_paragraph) {
-	if (0 <= p_paragraph && p_paragraph < main->lines.size()) {
+	int to_line = main->first_invalid_line.load();
+	if (0 <= p_paragraph && p_paragraph < to_line) {
 		return main->lines[p_paragraph].offset.y;
 	}
 	return 0;
@@ -3928,7 +4164,9 @@ float RichTextLabel::get_paragraph_offset(int p_paragraph) {
 
 int RichTextLabel::get_line_count() const {
 	int line_count = 0;
-	for (int i = 0; i < main->lines.size(); i++) {
+	int to_line = main->first_invalid_line.load();
+	for (int i = 0; i < to_line; i++) {
+		MutexLock lock(main->lines[i].text_buf->get_mutex());
 		line_count += main->lines[i].text_buf->get_line_count();
 	}
 	return line_count;
@@ -3989,13 +4227,13 @@ bool RichTextLabel::_search_table(ItemTable *p_table, List<Item *>::Element *p_f
 		ERR_CONTINUE(E->get()->type != ITEM_FRAME); // Children should all be frames.
 		ItemFrame *frame = static_cast<ItemFrame *>(E->get());
 		if (p_reverse_search) {
-			for (int i = frame->lines.size() - 1; i >= 0; i--) {
+			for (int i = (int)frame->lines.size() - 1; i >= 0; i--) {
 				if (_search_line(frame, i, p_string, -1, p_reverse_search)) {
 					return true;
 				}
 			}
 		} else {
-			for (int i = 0; i < frame->lines.size(); i++) {
+			for (int i = 0; i < (int)frame->lines.size(); i++) {
 				if (_search_line(frame, i, p_string, 0, p_reverse_search)) {
 					return true;
 				}
@@ -4008,12 +4246,12 @@ bool RichTextLabel::_search_table(ItemTable *p_table, List<Item *>::Element *p_f
 
 bool RichTextLabel::_search_line(ItemFrame *p_frame, int p_line, const String &p_string, int p_char_idx, bool p_reverse_search) {
 	ERR_FAIL_COND_V(p_frame == nullptr, false);
-	ERR_FAIL_COND_V(p_line < 0 || p_line >= p_frame->lines.size(), false);
+	ERR_FAIL_COND_V(p_line < 0 || p_line >= (int)p_frame->lines.size(), false);
 
-	Line &l = p_frame->lines.write[p_line];
+	Line &l = p_frame->lines[p_line];
 
 	String text;
-	Item *it_to = (p_line + 1 < p_frame->lines.size()) ? p_frame->lines[p_line + 1].from : nullptr;
+	Item *it_to = (p_line + 1 < (int)p_frame->lines.size()) ? p_frame->lines[p_line + 1].from : nullptr;
 	for (Item *it = l.from; it && it != it_to; it = _get_next_item(it)) {
 		switch (it->type) {
 			case ITEM_NEWLINE: {
@@ -4071,7 +4309,8 @@ bool RichTextLabel::search(const String &p_string, bool p_from_selection, bool p
 
 	int char_idx = p_search_previous ? -1 : 0;
 	int current_line = 0;
-	int ending_line = main->lines.size() - 1;
+	int to_line = main->first_invalid_line.load();
+	int ending_line = to_line - 1;
 	if (p_from_selection && selection.active) {
 		// First check to see if other results exist in current line
 		char_idx = p_search_previous ? selection.from_char - 1 : selection.to_char;
@@ -4120,8 +4359,8 @@ bool RichTextLabel::search(const String &p_string, bool p_from_selection, bool p
 	while (current_line != ending_line) {
 		// Wrap around
 		if (current_line < 0) {
-			current_line = main->lines.size() - 1;
-		} else if (current_line >= main->lines.size()) {
+			current_line = to_line - 1;
+		} else if (current_line >= to_line) {
 			current_line = 0;
 		}
 
@@ -4143,12 +4382,13 @@ bool RichTextLabel::search(const String &p_string, bool p_from_selection, bool p
 
 String RichTextLabel::_get_line_text(ItemFrame *p_frame, int p_line, Selection p_selection) const {
 	String text;
+
 	ERR_FAIL_COND_V(p_frame == nullptr, text);
-	ERR_FAIL_COND_V(p_line < 0 || p_line >= p_frame->lines.size(), text);
+	ERR_FAIL_COND_V(p_line < 0 || p_line >= (int)p_frame->lines.size(), text);
 
-	Line &l = p_frame->lines.write[p_line];
+	Line &l = p_frame->lines[p_line];
 
-	Item *it_to = (p_line + 1 < p_frame->lines.size()) ? p_frame->lines[p_line + 1].from : nullptr;
+	Item *it_to = (p_line + 1 < (int)p_frame->lines.size()) ? p_frame->lines[p_line + 1].from : nullptr;
 	int end_idx = 0;
 	if (it_to != nullptr) {
 		end_idx = it_to->index;
@@ -4163,7 +4403,7 @@ String RichTextLabel::_get_line_text(ItemFrame *p_frame, int p_line, Selection p
 			for (Item *E : table->subitems) {
 				ERR_CONTINUE(E->type != ITEM_FRAME); // Children should all be frames.
 				ItemFrame *frame = static_cast<ItemFrame *>(E);
-				for (int i = 0; i < frame->lines.size(); i++) {
+				for (int i = 0; i < (int)frame->lines.size(); i++) {
 					text += _get_line_text(frame, i, p_selection);
 				}
 			}
@@ -4227,7 +4467,8 @@ String RichTextLabel::get_selected_text() const {
 	}
 
 	String text;
-	for (int i = 0; i < main->lines.size(); i++) {
+	int to_line = main->first_invalid_line.load();
+	for (int i = 0; i < to_line; i++) {
 		text += _get_line_text(main, i, selection);
 	}
 	return text;
@@ -4368,19 +4609,23 @@ String RichTextLabel::get_parsed_text() const {
 
 void RichTextLabel::set_text_direction(Control::TextDirection p_text_direction) {
 	ERR_FAIL_COND((int)p_text_direction < -1 || (int)p_text_direction > 3);
+	_stop_thread();
+
 	if (text_direction != p_text_direction) {
 		text_direction = p_text_direction;
-		main->first_invalid_line = 0; //invalidate ALL
-		_validate_line_caches(main);
+		main->first_invalid_line.store(0); //invalidate ALL
+		_validate_line_caches();
 		update();
 	}
 }
 
 void RichTextLabel::set_structured_text_bidi_override(TextServer::StructuredTextParser p_parser) {
 	if (st_parser != p_parser) {
+		_stop_thread();
+
 		st_parser = p_parser;
-		main->first_invalid_line = 0; //invalidate ALL
-		_validate_line_caches(main);
+		main->first_invalid_line.store(0); //invalidate ALL
+		_validate_line_caches();
 		update();
 	}
 }
@@ -4390,10 +4635,14 @@ TextServer::StructuredTextParser RichTextLabel::get_structured_text_bidi_overrid
 }
 
 void RichTextLabel::set_structured_text_bidi_override_options(Array p_args) {
-	st_args = p_args;
-	main->first_invalid_line = 0; //invalidate ALL
-	_validate_line_caches(main);
-	update();
+	if (st_args != p_args) {
+		_stop_thread();
+
+		st_args = p_args;
+		main->first_invalid_line.store(0); //invalidate ALL
+		_validate_line_caches();
+		update();
+	}
 }
 
 Array RichTextLabel::get_structured_text_bidi_override_options() const {
@@ -4406,9 +4655,11 @@ Control::TextDirection RichTextLabel::get_text_direction() const {
 
 void RichTextLabel::set_language(const String &p_language) {
 	if (language != p_language) {
+		_stop_thread();
+
 		language = p_language;
-		main->first_invalid_line = 0; //invalidate ALL
-		_validate_line_caches(main);
+		main->first_invalid_line.store(0); //invalidate ALL
+		_validate_line_caches();
 		update();
 	}
 }
@@ -4419,9 +4670,11 @@ String RichTextLabel::get_language() const {
 
 void RichTextLabel::set_autowrap_mode(RichTextLabel::AutowrapMode p_mode) {
 	if (autowrap_mode != p_mode) {
+		_stop_thread();
+
 		autowrap_mode = p_mode;
 		main->first_invalid_line = 0; //invalidate ALL
-		_validate_line_caches(main);
+		_validate_line_caches();
 		update();
 	}
 }
@@ -4432,6 +4685,8 @@ RichTextLabel::AutowrapMode RichTextLabel::get_autowrap_mode() const {
 
 void RichTextLabel::set_percent_visible(float p_percent) {
 	if (percent_visible != p_percent) {
+		_stop_thread();
+
 		if (p_percent < 0 || p_percent >= 1) {
 			visible_characters = -1;
 			percent_visible = 1;
@@ -4440,8 +4695,8 @@ void RichTextLabel::set_percent_visible(float p_percent) {
 			percent_visible = p_percent;
 		}
 		if (visible_chars_behavior == VC_CHARS_BEFORE_SHAPING) {
-			main->first_invalid_line = 0; //invalidate ALL
-			_validate_line_caches(main);
+			main->first_invalid_line.store(0); //invalidate ALL
+			_validate_line_caches();
 		}
 		update();
 	}
@@ -4476,15 +4731,19 @@ void RichTextLabel::install_effect(const Variant effect) {
 
 int RichTextLabel::get_content_height() const {
 	int total_height = 0;
-	if (main->lines.size()) {
-		total_height = main->lines[main->lines.size() - 1].offset.y + main->lines[main->lines.size() - 1].text_buf->get_size().y + main->lines[main->lines.size() - 1].text_buf->get_line_count() * get_theme_constant(SNAME("line_separation"));
+	int to_line = main->first_invalid_line.load();
+	if (to_line) {
+		MutexLock lock(main->lines[to_line - 1].text_buf->get_mutex());
+		total_height = main->lines[to_line - 1].offset.y + main->lines[to_line - 1].text_buf->get_size().y + main->lines[to_line - 1].text_buf->get_line_count() * get_theme_constant(SNAME("line_separation"));
 	}
 	return total_height;
 }
 
 int RichTextLabel::get_content_width() const {
 	int total_width = 0;
-	for (int i = 0; i < main->lines.size(); i++) {
+	int to_line = main->first_invalid_line.load();
+	for (int i = 0; i < to_line; i++) {
+		MutexLock lock(main->lines[i].text_buf->get_mutex());
 		total_width = MAX(total_width, main->lines[i].offset.x + main->lines[i].text_buf->get_size().x);
 	}
 	return total_width;
@@ -4603,6 +4862,14 @@ void RichTextLabel::_bind_methods() {
 
 	ClassDB::bind_method(D_METHOD("get_text"), &RichTextLabel::get_text);
 
+	ClassDB::bind_method(D_METHOD("is_ready"), &RichTextLabel::is_ready);
+
+	ClassDB::bind_method(D_METHOD("set_threaded", "threaded"), &RichTextLabel::set_threaded);
+	ClassDB::bind_method(D_METHOD("is_threaded"), &RichTextLabel::is_threaded);
+
+	ClassDB::bind_method(D_METHOD("set_progress_bar_delay", "delay_ms"), &RichTextLabel::set_progress_bar_delay);
+	ClassDB::bind_method(D_METHOD("get_progress_bar_delay"), &RichTextLabel::get_progress_bar_delay);
+
 	ClassDB::bind_method(D_METHOD("set_visible_characters", "amount"), &RichTextLabel::set_visible_characters);
 	ClassDB::bind_method(D_METHOD("get_visible_characters"), &RichTextLabel::get_visible_characters);
 
@@ -4643,6 +4910,9 @@ void RichTextLabel::_bind_methods() {
 	// Note: set "bbcode_enabled" first, to avoid unnecessary "text" resets.
 	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "bbcode_enabled"), "set_use_bbcode", "is_using_bbcode");
 
+	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "threaded"), "set_threaded", "is_threaded");
+	ADD_PROPERTY(PropertyInfo(Variant::INT, "progress_bar_delay"), "set_progress_bar_delay", "get_progress_bar_delay");
+
 	ADD_PROPERTY(PropertyInfo(Variant::INT, "tab_size", PROPERTY_HINT_RANGE, "0,24,1"), "set_tab_size", "get_tab_size");
 	ADD_PROPERTY(PropertyInfo(Variant::STRING, "text", PROPERTY_HINT_MULTILINE_TEXT), "set_text", "get_text");
 	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "fit_content_height"), "set_fit_content_height", "is_fit_content_height_enabled");
@@ -4676,6 +4946,8 @@ void RichTextLabel::_bind_methods() {
 	ADD_SIGNAL(MethodInfo("meta_hover_started", PropertyInfo(Variant::NIL, "meta", PROPERTY_HINT_NONE, "", PROPERTY_USAGE_NIL_IS_VARIANT)));
 	ADD_SIGNAL(MethodInfo("meta_hover_ended", PropertyInfo(Variant::NIL, "meta", PROPERTY_HINT_NONE, "", PROPERTY_USAGE_NIL_IS_VARIANT)));
 
+	ADD_SIGNAL(MethodInfo("finished"));
+
 	BIND_ENUM_CONSTANT(AUTOWRAP_OFF);
 	BIND_ENUM_CONSTANT(AUTOWRAP_ARBITRARY);
 	BIND_ENUM_CONSTANT(AUTOWRAP_WORD);
@@ -4727,15 +4999,19 @@ RichTextLabel::VisibleCharactersBehavior RichTextLabel::get_visible_characters_b
 
 void RichTextLabel::set_visible_characters_behavior(RichTextLabel::VisibleCharactersBehavior p_behavior) {
 	if (visible_chars_behavior != p_behavior) {
+		_stop_thread();
+
 		visible_chars_behavior = p_behavior;
-		main->first_invalid_line = 0; //invalidate ALL
-		_validate_line_caches(main);
+		main->first_invalid_line.store(0); //invalidate ALL
+		_validate_line_caches();
 		update();
 	}
 }
 
 void RichTextLabel::set_visible_characters(int p_visible) {
 	if (visible_characters != p_visible) {
+		_stop_thread();
+
 		visible_characters = p_visible;
 		if (p_visible == -1) {
 			percent_visible = 1;
@@ -4746,8 +5022,8 @@ void RichTextLabel::set_visible_characters(int p_visible) {
 			}
 		}
 		if (visible_chars_behavior == VC_CHARS_BEFORE_SHAPING) {
-			main->first_invalid_line = 0; //invalidate ALL
-			_validate_line_caches(main);
+			main->first_invalid_line.store(0); //invalidate ALL
+			_validate_line_caches();
 		}
 		update();
 	}
@@ -4759,7 +5035,9 @@ int RichTextLabel::get_visible_characters() const {
 
 int RichTextLabel::get_character_line(int p_char) {
 	int line_count = 0;
-	for (int i = 0; i < main->lines.size(); i++) {
+	int to_line = main->first_invalid_line.load();
+	for (int i = 0; i < to_line; i++) {
+		MutexLock lock(main->lines[i].text_buf->get_mutex());
 		if (main->lines[i].char_offset < p_char && p_char <= main->lines[i].char_offset + main->lines[i].char_count) {
 			for (int j = 0; j < main->lines[i].text_buf->get_line_count(); j++) {
 				Vector2i range = main->lines[i].text_buf->get_line_range(j);
@@ -4777,7 +5055,8 @@ int RichTextLabel::get_character_line(int p_char) {
 
 int RichTextLabel::get_character_paragraph(int p_char) {
 	int para_count = 0;
-	for (int i = 0; i < main->lines.size(); i++) {
+	int to_line = main->first_invalid_line.load();
+	for (int i = 0; i < to_line; i++) {
 		if (main->lines[i].char_offset < p_char && p_char <= main->lines[i].char_offset + main->lines[i].char_count) {
 			return para_count;
 		} else {
@@ -4802,7 +5081,6 @@ int RichTextLabel::get_total_character_count() const {
 		}
 		it = _get_next_item(it, true);
 	}
-
 	return tc;
 }
 
@@ -4812,7 +5090,8 @@ int RichTextLabel::get_total_glyph_count() const {
 	while (it) {
 		if (it->type == ITEM_FRAME) {
 			ItemFrame *f = static_cast<ItemFrame *>(it);
-			for (int i = 0; i < f->lines.size(); i++) {
+			for (int i = 0; i < (int)f->lines.size(); i++) {
+				MutexLock lock(f->lines[i].text_buf->get_mutex());
 				tg += TS->shaped_text_get_glyph_count(f->lines[i].text_buf->get_rid());
 			}
 		}
@@ -4836,7 +5115,6 @@ Size2 RichTextLabel::get_minimum_size() const {
 	}
 
 	if (fit_content_height) {
-		const_cast<RichTextLabel *>(this)->_validate_line_caches(main);
 		size.y += get_content_height();
 	}
 
@@ -5034,10 +5312,10 @@ RichTextLabel::RichTextLabel(const String &p_text) {
 	main->index = 0;
 	current = main;
 	main->lines.resize(1);
-	main->lines.write[0].from = main;
-	main->first_invalid_line = 0;
-	main->first_resized_line = 0;
-	main->first_invalid_font_line = 0;
+	main->lines[0].from = main;
+	main->first_invalid_line.store(0);
+	main->first_resized_line.store(0);
+	main->first_invalid_font_line.store(0);
 	current_frame = main;
 
 	vscroll = memnew(VScrollBar);
@@ -5052,10 +5330,13 @@ RichTextLabel::RichTextLabel(const String &p_text) {
 	vscroll->hide();
 
 	set_text(p_text);
+	updating.store(false);
+	stop_thread.store(false);
 
 	set_clip_contents(true);
 }
 
 RichTextLabel::~RichTextLabel() {
+	_stop_thread();
 	memdelete(main);
 }
diff --git a/scene/gui/rich_text_label.h b/scene/gui/rich_text_label.h
index c6d0d0875d..7fbd5f1745 100644
--- a/scene/gui/rich_text_label.h
+++ b/scene/gui/rich_text_label.h
@@ -141,10 +141,10 @@ private:
 	struct ItemFrame : public Item {
 		bool cell = false;
 
-		Vector<Line> lines;
-		int first_invalid_line = 0;
-		int first_invalid_font_line = 0;
-		int first_resized_line = 0;
+		LocalVector<Line> lines;
+		std::atomic<int> first_invalid_line;
+		std::atomic<int> first_invalid_font_line;
+		std::atomic<int> first_resized_line;
 
 		ItemFrame *parent_frame = nullptr;
 
@@ -155,7 +155,12 @@ private:
 		Size2 max_size_over = Size2(-1, -1);
 		Rect2 padding;
 
-		ItemFrame() { type = ITEM_FRAME; }
+		ItemFrame() {
+			type = ITEM_FRAME;
+			first_invalid_line.store(0);
+			first_invalid_font_line.store(0);
+			first_resized_line.store(0);
+		}
 	};
 
 	struct ItemText : public Item {
@@ -263,8 +268,8 @@ private:
 			int width = 0;
 		};
 
-		Vector<Column> columns;
-		Vector<float> rows;
+		LocalVector<Column> columns;
+		LocalVector<float> rows;
 
 		int total_width = 0;
 		int total_height = 0;
@@ -363,6 +368,16 @@ private:
 	Item *current = nullptr;
 	ItemFrame *current_frame = nullptr;
 
+	Thread thread;
+	Mutex data_mutex;
+	bool threaded = false;
+	std::atomic<bool> stop_thread;
+	std::atomic<bool> updating;
+	std::atomic<double> loaded;
+
+	uint64_t loading_started = 0;
+	int progress_delay = 1000;
+
 	VScrollBar *vscroll = nullptr;
 
 	AutowrapMode autowrap_mode = AUTOWRAP_WORD_SMART;
@@ -392,7 +407,11 @@ private:
 	Array custom_effects;
 
 	void _invalidate_current_line(ItemFrame *p_frame);
-	void _validate_line_caches(ItemFrame *p_frame);
+
+	static void _thread_function(void *self);
+	void _stop_thread();
+	bool _validate_line_caches();
+	void _process_line_caches();
 
 	void _add_item(Item *p_item, bool p_enter = false, bool p_ensure_newline = false);
 	void _remove_item(Item *p_item, const int p_line, const int p_subitem_line);
@@ -446,8 +465,9 @@ private:
 	bool _search_line(ItemFrame *p_frame, int p_line, const String &p_string, int p_char_idx, bool p_reverse_search);
 	bool _search_table(ItemTable *p_table, List<Item *>::Element *p_from, const String &p_string, bool p_reverse_search);
 
-	void _shape_line(ItemFrame *p_frame, int p_line, const Ref<Font> &p_base_font, int p_base_font_size, int p_width, int *r_char_offset);
-	void _resize_line(ItemFrame *p_frame, int p_line, const Ref<Font> &p_base_font, int p_base_font_size, int p_width);
+	float _shape_line(ItemFrame *p_frame, int p_line, const Ref<Font> &p_base_font, int p_base_font_size, int p_width, float p_h, int *r_char_offset);
+	float _resize_line(ItemFrame *p_frame, int p_line, const Ref<Font> &p_base_font, int p_base_font_size, int p_width, float p_h);
+
 	void _update_line_font(ItemFrame *p_frame, int p_line, const Ref<Font> &p_base_font, int p_base_font_size);
 	int _draw_line(ItemFrame *p_frame, int p_line, const Vector2 &p_ofs, int p_width, const Color &p_base_color, int p_outline_size, const Color &p_outline_color, const Color &p_font_shadow_color, int p_shadow_outline_size, const Point2 &p_shadow_ofs, int &r_processed_glyphs);
 	float _find_click_in_line(ItemFrame *p_frame, int p_line, const Vector2 &p_ofs, int p_width, const Point2i &p_click, ItemFrame **r_click_frame = nullptr, int *r_click_line = nullptr, Item **r_click_item = nullptr, int *r_click_char = nullptr, bool p_table = false);
@@ -480,9 +500,9 @@ private:
 	bool _find_layout_subitem(Item *from, Item *to);
 	void _fetch_item_fx_stack(Item *p_item, Vector<ItemFX *> &r_stack);
 
-	void _update_scroll();
 	void _update_fx(ItemFrame *p_frame, double p_delta_time);
 	void _scroll_changed(double);
+	int _find_first_line(int p_from, int p_to, int p_vofs) const;
 
 	virtual void gui_input(const Ref<InputEvent> &p_event) override;
 	virtual String get_tooltip(const Point2 &p_pos) const override;
@@ -611,6 +631,14 @@ public:
 	bool is_deselect_on_focus_loss_enabled() const;
 	void deselect();
 
+	bool is_ready() const;
+
+	void set_threaded(bool p_threaded);
+	bool is_threaded() const;
+
+	void set_progress_bar_delay(int p_delay_ms);
+	int get_progress_bar_delay() const;
+
 	// Context menu.
 	PopupMenu *get_menu() const;
 	bool is_menu_visible() const;