View: prevent redundant measuring for performance reasons

No need to remeasure or relayout when nothing has changed

src/api-impl-jni/util.c

@@ -117,6 +117,7 @@ void set_up_handle_cache(JNIEnv *env)
 	handle_cache.view.getScrollY = _METHOD(handle_cache.view.class, "getScrollY", "()I");
 	handle_cache.view.performClick = _METHOD(handle_cache.view.class, "performClick", "()Z");
 	handle_cache.view.onTouchEvent = _METHOD(handle_cache.view.class, "onTouchEvent", "(Landroid/view/MotionEvent;)Z");
+	handle_cache.view.layoutInternal = _METHOD(handle_cache.view.class, "layoutInternal", "(II)V");
 
 	handle_cache.asset_manager.class = _REF((*env)->FindClass(env, "android/content/res/AssetManager"));
 	handle_cache.asset_manager.extractFromAPK = _STATIC_METHOD(handle_cache.asset_manager.class, "extractFromAPK", "(Ljava/lang/String;Ljava/lang/String;)V");

src/api-impl-jni/util.h

@@ -71,6 +71,7 @@ struct handle_cache {
 		jmethodID getScrollY;
 		jmethodID performClick;
 		jmethodID onTouchEvent;
+		jmethodID layoutInternal;
 	} view;
 	struct {
 		jclass class;

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

@@ -8,8 +8,6 @@
 #include "../generated_headers/android_view_ViewGroup.h"
 #include "../generated_headers/android_view_View.h"
 
-#define MEASURE_SPEC_EXACTLY (1 << 30)
-
 #define SOURCE_CLASS_POINTER 0x2
 
 struct _AndroidLayout {
@@ -41,17 +39,7 @@ static void android_layout_allocate(GtkLayoutManager *layout_manager, GtkWidget
 	AndroidLayout *layout = ATL_ANDROID_LAYOUT(layout_manager);
 	JNIEnv *env = get_jni_env();
 
-	(*env)->CallVoidMethod(env, layout->view, handle_cache.view.onMeasure, MEASURE_SPEC_EXACTLY | width, MEASURE_SPEC_EXACTLY | height);
+	(*env)->CallVoidMethod(env, layout->view, handle_cache.view.layoutInternal, width, height);
-	if((*env)->ExceptionCheck(env))
-		(*env)->ExceptionDescribe(env);
-
-	(*env)->CallVoidMethod(env, layout->view, handle_cache.view.computeScroll);
-	if((*env)->ExceptionCheck(env))
-		(*env)->ExceptionDescribe(env);
-	int scroll_x = (*env)->CallIntMethod(env, layout->view, handle_cache.view.getScrollX);
-	int scroll_y = (*env)->CallIntMethod(env, layout->view, handle_cache.view.getScrollY);
-
-	(*env)->CallVoidMethod(env, layout->view, handle_cache.view.onLayout, TRUE, scroll_x, scroll_y, width, height);
 	if((*env)->ExceptionCheck(env))
 		(*env)->ExceptionDescribe(env);
 }

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

@@ -806,6 +806,12 @@ public class View extends Object {
 
 	public static HashMap<Integer, View> view_by_id = new HashMap<Integer, View>();
 
+	private int oldWidthMeasureSpec;
+	private int oldHeightMeasureSpec;
+	private boolean layoutRequested;
+	private int oldWidth;
+	private int oldHeight;
+
 	public View() {
 		this(Context.this_application);
 	} // FIXME
@@ -1081,7 +1087,12 @@ public class View extends Object {
 	public void setOnHoverListener(OnHoverListener listener) {}
 
 	public final void measure(int widthMeasureSpec, int heightMeasureSpec) {
+		if (layoutRequested || widthMeasureSpec != oldWidthMeasureSpec || heightMeasureSpec != oldHeightMeasureSpec) {
+			oldWidthMeasureSpec = widthMeasureSpec;
+			oldHeightMeasureSpec = heightMeasureSpec;
 			onMeasure(widthMeasureSpec, heightMeasureSpec);
+			layoutRequested = false;
+		}
 	}
 
 	public final int getMeasuredState() {
@@ -1156,6 +1167,18 @@ public class View extends Object {
 		native_layout(widget, l, t, r, b);
 	}
 
+	/** Helper function to be called from GTKs LayoutManager via JNI */
+	private void 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);
+		}
+		boolean changed = oldWidth != width || oldHeight != height;
+		onLayout(changed, 0, 0, width, height);
+		oldWidth = width;
+		oldHeight = height;
+	}
+
 	public int getLeft() {
 		return left;
 	}
@@ -1190,6 +1213,7 @@ public class View extends Object {
 	public boolean removeCallbacks(Runnable action) {return false;}
 
 	public void requestLayout() {
+		layoutRequested = true;
 		native_requestLayout(widget);
 	};