View: call onLayout() only on size change or on request

GTK always wants us to call gtk_widget_allocate() on all children, so we
need to do it manually when not calling onLayout().

src/api-impl-jni/util.c

@@ -134,7 +134,7 @@ void set_up_handle_cache(JNIEnv *env)
 	handle_cache.view.onTouchEvent = _METHOD(handle_cache.view.class, "onTouchEvent", "(Landroid/view/MotionEvent;)Z");
 	handle_cache.view.dispatchTouchEvent = _METHOD(handle_cache.view.class, "dispatchTouchEvent", "(Landroid/view/MotionEvent;)Z");
 	handle_cache.view.onInterceptTouchEvent = _METHOD(handle_cache.view.class, "onInterceptTouchEvent", "(Landroid/view/MotionEvent;)Z");
-	handle_cache.view.layoutInternal = _METHOD(handle_cache.view.class, "layoutInternal", "(II)V");
+	handle_cache.view.layoutInternal = _METHOD(handle_cache.view.class, "layoutInternal", "(II)Z");
 	handle_cache.view.measure = _METHOD(handle_cache.view.class, "measure", "(II)V");
 	handle_cache.view.performLongClick = _METHOD(handle_cache.view.class, "performLongClick", "(FF)Z");
 	handle_cache.view.getId = _METHOD(handle_cache.view.class, "getId", "()I");

src/api-impl-jni/views/AndroidLayout.c

@@ -70,9 +70,18 @@ static void android_layout_allocate(GtkLayoutManager *layout_manager, GtkWidget
 		height = layout->real_height;
 	}
 
-	(*env)->CallVoidMethod(env, layout->view, handle_cache.view.layoutInternal, width, height);
+	jboolean layoutChanged = (*env)->CallBooleanMethod(env, layout->view, handle_cache.view.layoutInternal, width, height);
 	if((*env)->ExceptionCheck(env))
 		(*env)->ExceptionDescribe(env);
+	if (!layoutChanged) {  // No change in layout. Reapply the current allocations
+		for (GtkWidget *child = gtk_widget_get_first_child(widget); child; child = gtk_widget_get_next_sibling(child)) {
+			graphene_matrix_t transform_matrix;
+			if (gtk_widget_compute_transform(child, widget, &transform_matrix)) {
+				GskTransform *transform = gsk_transform_matrix(NULL, &transform_matrix);
+				gtk_widget_allocate(child, gtk_widget_get_width(child), gtk_widget_get_height(child), gtk_widget_get_baseline(child), transform);
+			}
+		}
+	}
 }
 
 static GtkSizeRequestMode android_layout_get_request_mode(GtkLayoutManager *layout_manager, GtkWidget *widget)

src/api-impl/android/view/View.java

@@ -847,6 +847,7 @@ public class View implements Drawable.Callback {
 	private int oldWidthMeasureSpec = -1;
 	private int oldHeightMeasureSpec = -1;
 	private boolean layoutRequested = true;
+	private boolean layoutPending = true;
 	private int oldWidth;
 	private int oldHeight;
 	protected boolean haveCustomMeasure = true;
@@ -1366,6 +1367,7 @@ public class View implements Drawable.Callback {
 			oldHeightMeasureSpec = heightMeasureSpec;
 			onMeasure(widthMeasureSpec, heightMeasureSpec);
 			layoutRequested = false;
+			layoutPending = true;
 		}
 	}
 
@@ -1441,8 +1443,10 @@ public class View implements Drawable.Callback {
 		native_layout(widget, l, t, r, b);
 	}
 
-	/** Helper function to be called from GTKs LayoutManager via JNI */
+	/** Helper function to be called from GTK's LayoutManager via JNI
-	private void layoutInternal(int width, int height) {
+	 * @return true if the layout changed
+	 */
+	private boolean layoutInternal(int width, int height) {
 		// if the layout is triggered from a native widget, we might not have measured yet
 		if (width != getMeasuredWidth() || height != getMeasuredHeight()) {
 			measure(width | MeasureSpec.EXACTLY, height | MeasureSpec.EXACTLY);
@@ -1452,9 +1456,15 @@ public class View implements Drawable.Callback {
 			onSizeChanged(width, height, oldWidth, oldHeight);
 		bottom = top + height;
 		right = left + width;
-		onLayout(changed, 0, 0, width, height);
+		if (changed || layoutPending) {
-		oldWidth = width;
+			layoutPending = false;
-		oldHeight = height;
+			onLayout(changed, 0, 0, width, height);
+			oldWidth = width;
+			oldHeight = height;
+			return true;
+		} else {
+			return false;
+		}
 	}
 
 	public int getLeft() {