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[GTK4] Draw plain Composite backgrounds as color nodes #3693

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Merged
akurtakov merged 1 commit into from
Oct 7, 2026
Merged

[GTK4] Draw plain Composite backgrounds as color nodes #3693

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27 changes: 20 additions & 7 deletions bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/Composite.java
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Original file line number Diff line number Diff line change
Expand Up @@ -540,9 +540,9 @@ void snapshotBackground (long handle, long snapshot) {
/*
* Draw the effective background before children are snapshotted.
*
* SWTFixed widget has no CSS background rule, thus obtain a Cairo
* context from the snapshot and delegate to drawBackground(), which
* paints the background image or color directly via Cairo.
* SWTFixed widget has no CSS background rule, thus append a color node
* for a background color, or obtain a Cairo context from the snapshot
* and delegate to drawBackground() for a background image.
*
* Skip when an explicit background color has been set (state & BACKGROUND):
* GTK4 renders the CSS provider background automatically before calling
Expand All @@ -562,10 +562,23 @@ void snapshotBackground (long handle, long snapshot) {
int height = (state & ZERO_HEIGHT) != 0 ? 0 : allocation.height;
long rect = Graphene.graphene_rect_alloc();
Graphene.graphene_rect_init(rect, 0, 0, width, height);
long cairo = GTK4.gtk_snapshot_append_cairo(snapshot, rect);
if (cairo != 0) {
drawBackground(control, 0, cairo, 0, 0, width, height);
Cairo.cairo_destroy(cairo);
if (control.backgroundImage == null) {
/*
* The snapshot of every ancestor runs again when a child is redrawn. A Cairo
* node cannot be diffed, so a new one damages its whole area and makes the
* renderer rasterize and upload it again in every frame. A color node is
* diffed by value, so an unchanged background damages nothing.
*/
boolean noBackgroundRegion = drawRegion && hooks(SWT.Paint) && cachedNoBackground;
if (!noBackgroundRegion) {
GTK4.gtk_snapshot_append_color(snapshot, control.getBackgroundGdkRGBA(), rect);
}
} else {
long cairo = GTK4.gtk_snapshot_append_cairo(snapshot, rect);
if (cairo != 0) {
drawBackground(control, 0, cairo, 0, 0, width, height);
Cairo.cairo_destroy(cairo);
}
}
Graphene.graphene_rect_free(rect);
}
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