Perfect FreeType-based outlines for DynamicFonts

- Implement outlines based on FreeType Stroker API. This allows
  artifact-free results, similar to what you will see in Web or any text
  editing tools. Outline is a part of DynamicFont rather than Label,
  because outlines have to be baked into the font's atlas. Font has a
  default outline_color and a Label can specify font_outline_modulator
  that will be multiplied with the Font's color to get the final result.

- draw_char now has to be called twice to fully render a text - first
  with p_outline == true for each character and then with
  p_outline == false for each character.

- Number of draw-calls is reduced from 5 to 2 per outlined character.

- Overall cleanup of DynamicFont code, extracted duplicated code pieces
  into separate methods.

- The change is backward-compatible - Labels still have outline
  properties that work exactly as they worked before.

Closes #16279.

1 files changed, 12 insertions, 10 deletions

diff --git a/scene/resources/dynamic_font_stb.cpp b/scene/resources/dynamic_font_stb.cpp
index 098b794a95..29f1106d16 100644
--- a/scene/resources/dynamic_font_stb.cpp
+++ b/scene/resources/dynamic_font_stb.cpp
@@ -162,7 +162,7 @@ Size2 DynamicFontAtSize::get_char_size(CharType p_char, CharType p_next) const {
 	return ret;
 }
 
-float DynamicFontAtSize::draw_char(RID p_canvas_item, const Point2 &p_pos, CharType p_char, CharType p_next, const Color &p_modulate) const {
+float DynamicFontAtSize::draw_char(RID p_canvas_item, const Point2 &p_pos, CharType p_char, CharType p_next, const Color &p_modulate, bool p_outline) const {
 
 	const_cast<DynamicFontAtSize *>(this)->_update_char(p_char);
 
@@ -172,13 +172,15 @@ float DynamicFontAtSize::draw_char(RID p_canvas_item, const Point2 &p_pos, CharT
 		return 0;
 	}
 
-	Point2 cpos = p_pos;
-	cpos.x += c->h_align;
-	cpos.y -= get_ascent();
-	cpos.y += c->v_align;
-	ERR_FAIL_COND_V(c->texture_idx < -1 || c->texture_idx >= textures.size(), 0);
-	if (c->texture_idx != -1)
-		VisualServer::get_singleton()->canvas_item_add_texture_rect_region(p_canvas_item, Rect2(cpos, c->rect.size), textures[c->texture_idx].texture->get_rid(), c->rect, p_modulate);
+	if (!p_outline) {
+		Point2 cpos = p_pos;
+		cpos.x += c->h_align;
+		cpos.y -= get_ascent();
+		cpos.y += c->v_align;
+		ERR_FAIL_COND_V(c->texture_idx < -1 || c->texture_idx >= textures.size(), 0);
+		if (c->texture_idx != -1)
+			VisualServer::get_singleton()->canvas_item_add_texture_rect_region(p_canvas_item, Rect2(cpos, c->rect.size), textures[c->texture_idx].texture->get_rid(), c->rect, p_modulate);
+	}
 
 	//textures[c->texture_idx].texture->draw(p_canvas_item,Vector2());
 
@@ -459,12 +461,12 @@ bool DynamicFont::is_distance_field_hint() const {
 	return false;
 }
 
-float DynamicFont::draw_char(RID p_canvas_item, const Point2 &p_pos, CharType p_char, CharType p_next, const Color &p_modulate) const {
+float DynamicFont::draw_char(RID p_canvas_item, const Point2 &p_pos, CharType p_char, CharType p_next, const Color &p_modulate, bool p_outline) const {
 
 	if (!data_at_size.is_valid())
 		return 0;
 
-	return data_at_size->draw_char(p_canvas_item, p_pos, p_char, p_next, p_modulate);
+	return data_at_size->draw_char(p_canvas_item, p_pos, p_char, p_next, p_modulate, p_outline);
 }
 
 DynamicFont::DynamicFont() {