Fix PaintListener for GTK3 Table and Tree widgets

GTK3 emits two draw-related signals:

* EXPOSE_EVENT_INVERSE (after=false) → before GTK draws items
* EXPOSE_EVENT (after=true) → after GTK draws items

SWT historically dispatched SWT.Paint during EXPOSE_EVENT_INVERSE.

For widgets like Table and Tree, GTK draws all rows/cells after this
point.
Result: anything drawn in a PaintListener was immediately overwritten.

Author: akurtakov

bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/Table.java

@@ -2310,7 +2310,12 @@ long gtk_draw (long widget, long cairo) {
 		return 0;
 	}
 	drawInheritedBackground (cairo);
-	return super.gtk_draw (widget, cairo);
+	if (GTK.GTK4) {
+		return super.gtk_draw (widget, cairo);
+	} else {
+		// On GTK3 super.gtk_draw will be lost by items drawing thus handle explicitly in windowProc.
+		return 0;
+	}
 }
 
 @Override
@@ -4116,6 +4121,13 @@ long windowProc (long handle, long arg0, long user_data) {
 				}
 				propagateDraw(handle, arg0);
 			}
+			/*
+			 * Ensure the paint listener's drawing appears on top of items rather than being
+			 * overwritten by them.
+			 */
+			if (!GTK.GTK4) {
+				gtk3_paintEvent(arg0);
+			}
 			break;
 		}
 		case EXPOSE_EVENT_INVERSE: {
@@ -4194,6 +4206,33 @@ void checkSetDataInProcessBeforeRemoval(int start, int end) {
 	}
 }
 
+/**
+ * Fire the paint event explicitly, so the paint listener's drawing is not lost.
+ */
+private void gtk3_paintEvent(long cairo) {
+	if ((state & OBSCURED) != 0) return;
+	if (drawRegion) {
+		cairoClipRegion(cairo);
+	}
+	if (!hooksPaint()) return;
+	GdkRectangle rect = new GdkRectangle();
+	GDK.gdk_cairo_get_clip_rectangle(cairo, rect);
+	Event event = new Event();
+	event.count = 1;
+	Rectangle eventBounds = new Rectangle(rect.x, rect.y, rect.width, rect.height);
+	if ((style & SWT.MIRRORED) != 0) eventBounds.x = getClientWidth() - eventBounds.width - eventBounds.x;
+	event.setBounds(eventBounds);
+	GCData data = new GCData();
+	if (drawRegion) data.regionSet = eventRegion;
+	data.cairo = cairo;
+	GC gc = event.gc = GC.gtk_new(this, data);
+	gc.setClipping(eventBounds.x, eventBounds.y, eventBounds.width, eventBounds.height);
+	drawWidget(gc);
+	sendEvent(SWT.Paint, event);
+	gc.dispose();
+	event.gc = null;
+}
+
 @Override
 public void dispose() {
 	super.dispose();

bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/Tree.java

@@ -2480,7 +2480,12 @@ long gtk_draw (long widget, long cairo) {
 		return 0;
 	}
 	drawInheritedBackground	(cairo);
-	return super.gtk_draw (widget, cairo);
+	if (GTK.GTK4) {
+		return super.gtk_draw (widget, cairo);
+	} else {
+		// On GTK3 super.gtk_draw will be lost by items drawing thus handle explicitly in windowProc.
+		return 0;
+	}
 }
 
 @Override
@@ -4192,6 +4197,13 @@ long windowProc (long handle, long arg0, long user_data) {
 				}
 				propagateDraw(handle, arg0);
 			}
+			/*
+			 * Ensure the paint listener's drawing appears on top of items rather than being
+			 * overwritten by them.
+			 */
+			if (!GTK.GTK4) {
+				gtk3_paintEvent(arg0);
+			}
 			break;
 		}
 		case EXPOSE_EVENT_INVERSE: {
@@ -4267,6 +4279,33 @@ void checkSetDataInProcessBeforeRemoval() {
 	}
 }
 
+/**
+ * Fire the paint event explicitly, so the paint listener's drawing is not lost.
+ */
+private void gtk3_paintEvent(long cairo) {
+	if ((state & OBSCURED) != 0) return;
+	if (drawRegion) {
+		cairoClipRegion(cairo);
+	}
+	if (!hooksPaint()) return;
+	GdkRectangle rect = new GdkRectangle();
+	GDK.gdk_cairo_get_clip_rectangle(cairo, rect);
+	Event event = new Event();
+	event.count = 1;
+	Rectangle eventBounds = new Rectangle(rect.x, rect.y, rect.width, rect.height);
+	if ((style & SWT.MIRRORED) != 0) eventBounds.x = getClientWidth() - eventBounds.width - eventBounds.x;
+	event.setBounds(eventBounds);
+	GCData data = new GCData();
+	if (drawRegion) data.regionSet = eventRegion;
+	data.cairo = cairo;
+	GC gc = event.gc = GC.gtk_new(this, data);
+	gc.setClipping(eventBounds.x, eventBounds.y, eventBounds.width, eventBounds.height);
+	drawWidget(gc);
+	sendEvent(SWT.Paint, event);
+	gc.dispose();
+	event.gc = null;
+}
+
 private void throwCannotRemoveItem(int i) {
 	String message = "Cannot remove item with index " + i + ".";
 	throw new SWTException(message);