Fix invalid frame index when Sprite2D's hframes or vframes has been changed

(cherry picked from commit 484c5b5aff6e513a92baf5d3ddcae8bc8941ee26)

doc/classes/Sprite2D.xml

@@ -60,13 +60,13 @@
 			If [code]true[/code], texture is flipped vertically.
 		</member>
 		<member name="frame" type="int" setter="set_frame" getter="get_frame" default="0">
-			Current frame to display from sprite sheet. [member hframes] or [member vframes] must be greater than 1.
+			Current frame to display from sprite sheet. [member hframes] or [member vframes] must be greater than 1. This property is automatically adjusted when [member hframes] or [member vframes] are changed to keep pointing to the same visual frame (same column and row). If that's impossible, this value is reset to [code]0[/code].
 		</member>
 		<member name="frame_coords" type="Vector2i" setter="set_frame_coords" getter="get_frame_coords" default="Vector2i(0, 0)">
 			Coordinates of the frame to display from sprite sheet. This is as an alias for the [member frame] property. [member hframes] or [member vframes] must be greater than 1.
 		</member>
 		<member name="hframes" type="int" setter="set_hframes" getter="get_hframes" default="1">
-			The number of columns in the sprite sheet.
+			The number of columns in the sprite sheet. When this property is changed, [member frame] is adjusted so that the same visual frame is maintained (same row and column). If that's impossible, [member frame] is reset to [code]0[/code].
 		</member>
 		<member name="offset" type="Vector2" setter="set_offset" getter="get_offset" default="Vector2(0, 0)">
 			The texture's drawing offset.
@@ -84,7 +84,7 @@
 			[Texture2D] object to draw.
 		</member>
 		<member name="vframes" type="int" setter="set_vframes" getter="get_vframes" default="1">
-			The number of rows in the sprite sheet.
+			The number of rows in the sprite sheet. When this property is changed, [member frame] is adjusted so that the same visual frame is maintained (same row and column). If that's impossible, [member frame] is reset to [code]0[/code].
 		</member>
 	</members>
 	<signals>

doc/classes/Sprite3D.xml

@@ -10,13 +10,13 @@
 	</tutorials>
 	<members>
 		<member name="frame" type="int" setter="set_frame" getter="get_frame" default="0">
-			Current frame to display from sprite sheet. [member hframes] or [member vframes] must be greater than 1.
+			Current frame to display from sprite sheet. [member hframes] or [member vframes] must be greater than 1. This property is automatically adjusted when [member hframes] or [member vframes] are changed to keep pointing to the same visual frame (same column and row). If that's impossible, this value is reset to [code]0[/code].
 		</member>
 		<member name="frame_coords" type="Vector2i" setter="set_frame_coords" getter="get_frame_coords" default="Vector2i(0, 0)">
 			Coordinates of the frame to display from sprite sheet. This is as an alias for the [member frame] property. [member hframes] or [member vframes] must be greater than 1.
 		</member>
 		<member name="hframes" type="int" setter="set_hframes" getter="get_hframes" default="1">
-			The number of columns in the sprite sheet.
+			The number of columns in the sprite sheet. When this property is changed, [member frame] is adjusted so that the same visual frame is maintained (same row and column). If that's impossible, [member frame] is reset to [code]0[/code].
 		</member>
 		<member name="region_enabled" type="bool" setter="set_region_enabled" getter="is_region_enabled" default="false">
 			If [code]true[/code], the sprite will use [member region_rect] and display only the specified part of its texture.
@@ -28,7 +28,7 @@
 			[Texture2D] object to draw. If [member GeometryInstance3D.material_override] is used, this will be overridden. The size information is still used.
 		</member>
 		<member name="vframes" type="int" setter="set_vframes" getter="get_vframes" default="1">
-			The number of rows in the sprite sheet.
+			The number of rows in the sprite sheet. When this property is changed, [member frame] is adjusted so that the same visual frame is maintained (same row and column). If that's impossible, [member frame] is reset to [code]0[/code].
 		</member>
 	</members>
 	<signals>

scene/2d/sprite_2d.cpp

@@ -261,6 +261,9 @@ Vector2i Sprite2D::get_frame_coords() const {
 void Sprite2D::set_vframes(int p_amount) {
 	ERR_FAIL_COND_MSG(p_amount < 1, "Amount of vframes cannot be smaller than 1.");
 	vframes = p_amount;
+	if (frame >= vframes * hframes) {
+		frame = 0;
+	}
 	queue_redraw();
 	item_rect_changed();
 	notify_property_list_changed();
@@ -272,7 +275,21 @@ int Sprite2D::get_vframes() const {
 
 void Sprite2D::set_hframes(int p_amount) {
 	ERR_FAIL_COND_MSG(p_amount < 1, "Amount of hframes cannot be smaller than 1.");
+	if (vframes > 1) {
+		// Adjust the frame to fit new sheet dimensions.
+		int original_column = frame % hframes;
+		if (original_column >= p_amount) {
+			// Frame's column was dropped, reset.
+			frame = 0;
+		} else {
+			int original_row = frame / hframes;
+			frame = original_row * p_amount + original_column;
+		}
+	}
 	hframes = p_amount;
+	if (frame >= vframes * hframes) {
+		frame = 0;
+	}
 	queue_redraw();
 	item_rect_changed();
 	notify_property_list_changed();

scene/3d/sprite_3d.cpp

@@ -804,8 +804,11 @@ Vector2i Sprite3D::get_frame_coords() const {
 }
 
 void Sprite3D::set_vframes(int p_amount) {
-	ERR_FAIL_COND(p_amount < 1);
+	ERR_FAIL_COND_MSG(p_amount < 1, "Amount of vframes cannot be smaller than 1.");
 	vframes = p_amount;
+	if (frame >= vframes * hframes) {
+		frame = 0;
+	}
 	_queue_redraw();
 	notify_property_list_changed();
 }
@@ -815,8 +818,22 @@ int Sprite3D::get_vframes() const {
 }
 
 void Sprite3D::set_hframes(int p_amount) {
-	ERR_FAIL_COND(p_amount < 1);
+	ERR_FAIL_COND_MSG(p_amount < 1, "Amount of hframes cannot be smaller than 1.");
+	if (vframes > 1) {
+		// Adjust the frame to fit new sheet dimensions.
+		int original_column = frame % hframes;
+		if (original_column >= p_amount) {
+			// Frame's column was dropped, reset.
+			frame = 0;
+		} else {
+			int original_row = frame / hframes;
+			frame = original_row * p_amount + original_column;
+		}
+	}
 	hframes = p_amount;
+	if (frame >= vframes * hframes) {
+		frame = 0;
+	}
 	_queue_redraw();
 	notify_property_list_changed();
 }