Add option to keep margins when changing anchors, closes #3979

Amend: Fixed an issue for non-tool builds
Amend2: Same, just fixed doing nothing at some times

3 files changed, 32 insertions, 13 deletions

diff --git a/doc/base/classes.xml b/doc/base/classes.xml
index d111569a60..04e08f166e 100644
--- a/doc/base/classes.xml
+++ b/doc/base/classes.xml
@@ -8385,8 +8385,12 @@
 			</argument>
 			<argument index="1" name="anchor_mode" type="int">
 			</argument>
+			<argument index="2" name="keep_margin" type="bool" default="false">
+			</argument>
 			<description>
-			Change the anchor (ANCHOR_BEGIN, ANCHOR_END, ANCHOR_RATIO) type for a margin (MARGIN_LEFT, MARGIN_TOP, MARGIN_RIGHT, MARGIN_BOTTOM). Changing the anchor mode converts the current margin offset from the previous anchor mode to the new one, so margin offsets ([method set_margin]) must be done after setting anchors, or at the same time ([method set_anchor_and_margin]).
+			Change the anchor (ANCHOR_BEGIN, ANCHOR_END, ANCHOR_RATIO) type for a margin (MARGIN_LEFT, MARGIN_TOP, MARGIN_RIGHT, MARGIN_BOTTOM). Changing the anchor mode converts the current margin offset from the previous anchor mode to the new one, so margin offsets ([method set_margin]) must be done after setting anchors, or at the same time ([method set_anchor_and_margin])
+			
+			Additionally, [code]keep_margin[/code] controls whether margins should be left the same, or changed to keep the same position and size on-screen.
 			</description>
 		</method>
 		<method name="get_anchor" qualifiers="const">
diff --git a/scene/gui/control.cpp b/scene/gui/control.cpp
index 295ec03702..0364f73275 100644
--- a/scene/gui/control.cpp
+++ b/scene/gui/control.cpp
@@ -39,6 +39,9 @@
 #include "scene/scene_string_names.h"
 #include "scene/gui/panel.h"
 #include "scene/gui/label.h"
+#ifdef TOOLS_ENABLED
+#include "tools/editor/editor_settings.h"
+#endif
 #include <stdio.h>
 
 
@@ -1153,20 +1156,31 @@ float Control::_a2s(float p_val, AnchorType p_anchor,float p_range) const {
 }
 
 
-void Control::set_anchor(Margin p_margin,AnchorType p_anchor) {
+void Control::set_anchor(Margin p_margin,AnchorType p_anchor, bool p_keep_margin) {
 
 	if (!is_inside_tree()) {
 
-		data.anchor[p_margin]=p_anchor;
-	} else {
+		data.anchor[p_margin] = p_anchor;
+	} else if(!p_keep_margin) {
 		float pr = _get_parent_range(p_margin);
 		float s = _a2s( data.margin[p_margin], data.anchor[p_margin], pr );
-		data.anchor[p_margin]=p_anchor;
+		data.anchor[p_margin] = p_anchor;
 		data.margin[p_margin] = _s2a( s, p_anchor, pr );
+	} else {
+		data.anchor[p_margin] = p_anchor;
+		_size_changed();
 	}
 	_change_notify();
 }
 
+void Control::_set_anchor(Margin p_margin,AnchorType p_anchor) {
+	#ifdef TOOLS_ENABLED
+	set_anchor(p_margin, p_anchor, EDITOR_DEF("2d_editor/keep_margins_when_changing_anchors", false));
+	#else
+	set_anchor(p_margin, p_anchor);
+	#endif
+}
+
 void Control::set_anchor_and_margin(Margin p_margin,AnchorType p_anchor, float p_pos) {
 
 	set_anchor(p_margin,p_anchor);
@@ -2090,7 +2104,8 @@ void Control::_bind_methods() {
 	ObjectTypeDB::bind_method(_MD("accept_event"),&Control::accept_event);
 	ObjectTypeDB::bind_method(_MD("get_minimum_size"),&Control::get_minimum_size);
 	ObjectTypeDB::bind_method(_MD("get_combined_minimum_size"),&Control::get_combined_minimum_size);
-	ObjectTypeDB::bind_method(_MD("set_anchor","margin","anchor_mode"),&Control::set_anchor);
+	ObjectTypeDB::bind_method(_MD("set_anchor","margin","anchor_mode","keep_margin"),&Control::set_anchor,DEFVAL(false));
+	ObjectTypeDB::bind_method(_MD("_set_anchor","margin","anchor_mode"),&Control::_set_anchor);
 	ObjectTypeDB::bind_method(_MD("get_anchor","margin"),&Control::get_anchor);
 	ObjectTypeDB::bind_method(_MD("set_margin","margin","offset"),&Control::set_margin);
 	ObjectTypeDB::bind_method(_MD("set_anchor_and_margin","margin","anchor_mode","offset"),&Control::set_anchor_and_margin);
@@ -2184,10 +2199,10 @@ void Control::_bind_methods() {
 	BIND_VMETHOD(MethodInfo(Variant::BOOL,"can_drop_data",PropertyInfo(Variant::VECTOR2,"pos"),PropertyInfo(Variant::NIL,"data")));
 	BIND_VMETHOD(MethodInfo("drop_data",PropertyInfo(Variant::VECTOR2,"pos"),PropertyInfo(Variant::NIL,"data")));
 
-	ADD_PROPERTYINZ( PropertyInfo(Variant::INT,"anchor/left", PROPERTY_HINT_ENUM, "Begin,End,Ratio,Center"), _SCS("set_anchor"),_SCS("get_anchor"), MARGIN_LEFT );
-	ADD_PROPERTYINZ( PropertyInfo(Variant::INT,"anchor/top", PROPERTY_HINT_ENUM, "Begin,End,Ratio,Center"), _SCS("set_anchor"),_SCS("get_anchor"), MARGIN_TOP );
-	ADD_PROPERTYINZ( PropertyInfo(Variant::INT,"anchor/right", PROPERTY_HINT_ENUM, "Begin,End,Ratio,Center"), _SCS("set_anchor"),_SCS("get_anchor"), MARGIN_RIGHT );
-	ADD_PROPERTYINZ( PropertyInfo(Variant::INT,"anchor/bottom", PROPERTY_HINT_ENUM, "Begin,End,Ratio,Center"), _SCS("set_anchor"),_SCS("get_anchor"), MARGIN_BOTTOM );
+	ADD_PROPERTYINZ( PropertyInfo(Variant::INT,"anchor/left", PROPERTY_HINT_ENUM, "Begin,End,Ratio,Center"), _SCS("_set_anchor"),_SCS("get_anchor"), MARGIN_LEFT );
+	ADD_PROPERTYINZ( PropertyInfo(Variant::INT,"anchor/top", PROPERTY_HINT_ENUM, "Begin,End,Ratio,Center"), _SCS("_set_anchor"),_SCS("get_anchor"), MARGIN_TOP );
+	ADD_PROPERTYINZ( PropertyInfo(Variant::INT,"anchor/right", PROPERTY_HINT_ENUM, "Begin,End,Ratio,Center"), _SCS("_set_anchor"),_SCS("get_anchor"), MARGIN_RIGHT );
+	ADD_PROPERTYINZ( PropertyInfo(Variant::INT,"anchor/bottom", PROPERTY_HINT_ENUM, "Begin,End,Ratio,Center"), _SCS("_set_anchor"),_SCS("get_anchor"), MARGIN_BOTTOM );
 
 	ADD_PROPERTYINZ( PropertyInfo(Variant::INT,"margin/left", PROPERTY_HINT_RANGE, "-4096,4096"), _SCS("set_margin"),_SCS("get_margin"), MARGIN_LEFT );
 	ADD_PROPERTYINZ( PropertyInfo(Variant::INT,"margin/top", PROPERTY_HINT_RANGE, "-4096,4096"), _SCS("set_margin"),_SCS("get_margin"), MARGIN_TOP );
@@ -2304,5 +2319,3 @@ Control::Control() {
 Control::~Control()
 {
 }
-
-
diff --git a/scene/gui/control.h b/scene/gui/control.h
index 851d8316fb..1e2db7a575 100644
--- a/scene/gui/control.h
+++ b/scene/gui/control.h
@@ -162,6 +162,8 @@ private:
 	Control *_get_focus_neighbour(Margin p_margin,int p_count=0);
 
 
+	void _set_anchor(Margin p_margin,AnchorType p_anchor);
+
 	float _get_parent_range(int p_idx) const;
 	float _get_range(int p_idx) const;
 	float _s2a(float p_val, AnchorType p_anchor,float p_range) const;
@@ -244,7 +246,7 @@ public:
 
 	/* POSITIONING */
 
-	void set_anchor(Margin p_margin,AnchorType p_anchor);
+	void set_anchor(Margin p_margin,AnchorType p_anchor, bool p_keep_margin=false);
 	void set_anchor_and_margin(Margin p_margin,AnchorType p_anchor, float p_pos);
 
 	AnchorType get_anchor(Margin p_margin) const;