Enable scrollable divs.

Force a composite layer when the style says the content is scrollable.
Record the border and background in the main content picture.  When
the contents of the layer are bigger than the size, record the
foreground contents in a separate picture which is clipped by the
border and size.

When updating the base layer, remember the scroll position of each
layer and update the new layer with the same position.

Bug: 1566791
Change-Id: If440e4f215db6bda9df32a781d754d1f5a238162

1 files changed, 70 insertions, 0 deletions

diff --git a/WebKit/android/nav/WebView.cpp b/WebKit/android/nav/WebView.cpp
index 5154b42..aad3501 100644
--- a/WebKit/android/nav/WebView.cpp
+++ b/WebKit/android/nav/WebView.cpp
@@ -920,6 +920,19 @@ bool motionUp(int x, int y, int slop)
     return pageScrolled;
 }
 
+const LayerAndroid* scrollableLayer(int x, int y)
+{
+#if ENABLE(ANDROID_OVERFLOW_SCROLL) && USE(ACCELERATED_COMPOSITING)
+    const LayerAndroid* root = compositeRoot();
+    if (!root)
+        return 0;
+    const LayerAndroid* result = root->find(x, y);
+    if (result != 0 && result->contentIsScrollable())
+        return result;
+#endif
+    return 0;
+}
+
 int getBlockLeftEdge(int x, int y, float scale)
 {
     CachedRoot* root = getFrameCache(AllowNewer);
@@ -1200,8 +1213,27 @@ LayerAndroid* compositeRoot() const
         return 0;
 }
 
+static void copyScrollPositionRecursive(const LayerAndroid* from,
+                                        LayerAndroid* root)
+{
+    if (!from || !root)
+        return;
+    for (int i = 0; i < from->countChildren(); i++) {
+        const LayerAndroid* l = from->getChild(i);
+        if (l->contentIsScrollable()) {
+            LayerAndroid* match =
+                    const_cast<LayerAndroid*>(root->findById(l->uniqueId()));
+            if (match != 0)
+                match->setScrollPosition(l->scrollPosition());
+        }
+        copyScrollPositionRecursive(l, root);
+    }
+}
+
 void setBaseLayer(BaseLayerAndroid* layer)
 {
+    copyScrollPositionRecursive(compositeRoot(),
+            static_cast<LayerAndroid*>(layer->getChild(0)));
     delete m_baseLayer;
     m_baseLayer = layer;
     CachedRoot* root = getFrameCache(DontAllowNewer);
@@ -2064,6 +2096,40 @@ static void nativeDumpDisplayTree(JNIEnv* env, jobject jwebview, jstring jurl)
 #endif
 }
 
+static int nativeScrollableLayer(JNIEnv* env, jobject jwebview, jint x, jint y)
+{
+    WebView* view = GET_NATIVE_VIEW(env, jwebview);
+    LOG_ASSERT(view, "view not set in %s", __FUNCTION__);
+    return (int) view->scrollableLayer(x, y);
+}
+
+static bool validLayer(const LayerAndroid* root, const LayerAndroid* layer) {
+    if (root == layer)
+        return true;
+    for (int i = 0; i < root->countChildren(); i++) {
+        const LayerAndroid* l = root->getChild(i);
+        if (validLayer(l, layer))
+            return true;
+    }
+    return false;
+}
+
+static bool nativeScrollLayer(JNIEnv* env, jobject obj, jint pLayer, jint dx,
+        jint dy)
+{
+#if ENABLE(ANDROID_OVERFLOW_SCROLL)
+    WebView* view = GET_NATIVE_VIEW(env, obj);
+    const LayerAndroid* root = view->compositeRoot();
+    LayerAndroid* layer = (LayerAndroid*) pLayer;
+    if (!validLayer(root, layer)) {
+        return false;
+    }
+    LOG_ASSERT(layer, "layer not set in %s", __FUNCTION__);
+    return layer->scrollBy(dx, dy);
+#endif
+    return false;
+}
+
 /*
  * JNI registration
  */
@@ -2220,6 +2286,10 @@ static JNINativeMethod gJavaWebViewMethods[] = {
         (void*) nativeWordSelection },
     { "nativeGetBlockLeftEdge", "(IIF)I",
         (void*) nativeGetBlockLeftEdge },
+    { "nativeScrollableLayer", "(II)I",
+        (void*) nativeScrollableLayer },
+    { "nativeScrollLayer", "(III)Z",
+        (void*) nativeScrollLayer },
 };
 
 int register_webview(JNIEnv* env)