Implement pinch-zoom scaling for main-frame scrollbars and pinch-zoom overlay scrollbars.

cc/layer_tree_host.cc

Index: cc/layer_tree_host.cc
diff --git a/cc/layer_tree_host.cc b/cc/layer_tree_host.cc
index bc137893f8abbc4bc8a087dd596c4dd626a9cfcf..af1f4b39170bb5f0a7360aee16191d09a7f5b314 100644
--- a/cc/layer_tree_host.cc
+++ b/cc/layer_tree_host.cc
@@ -23,7 +23,11 @@
 #include "cc/math_util.h"
 #include "cc/occlusion_tracker.h"
 #include "cc/overdraw_metrics.h"
+#include "cc/pinch_zoom_scrollbar.h"
+#include "cc/pinch_zoom_scrollbar_geometry.h"
+#include "cc/pinch_zoom_scrollbar_painter.h"
 #include "cc/prioritized_resource_manager.h"
+#include "cc/scrollbar_layer.h"
 #include "cc/single_thread_proxy.h"
 #include "cc/switches.h"
 #include "cc/thread.h"
@@ -328,6 +332,11 @@ void LayerTreeHost::finishCommitOnImplThread(LayerTreeHostImpl* hostImpl)
             syncTree->ResetContentsTexturesPurged();
     }
 
+    syncTree->SetPinchZoomHorizontalLayerId(
+        m_pinchZoomScrollbarHorizontal ? m_pinchZoomScrollbarHorizontal->id() : 0);

[jamesr, 2013/02/26 20:48:46]

we use -1 as an invalid id most of the time

[wjmaclean, 2013/03/01 15:30:32]

Fixed.

+    syncTree->SetPinchZoomVerticalLayerId(
+        m_pinchZoomScrollbarVertical ? m_pinchZoomScrollbarVertical->id() : 0);
+
     if (!m_settings.implSidePainting) {
         // If we're not in impl-side painting, the tree is immediately
         // considered active.
@@ -340,6 +349,68 @@ void LayerTreeHost::finishCommitOnImplThread(LayerTreeHostImpl* hostImpl)
     m_commitNumber++;
 }
 
+void LayerTreeHost::setPinchZoomScrollbarPropertiesIfNeeded()
+{
+    if (!m_pinchZoomScrollbarHorizontal || !m_pinchZoomScrollbarVertical)
+        return;
+
+    gfx::Size size = layoutViewportSize();
+    int trackWidth = PinchZoomScrollbar::kTrackWidth;
+    Layer* rootScrollLayer = this->rootScrollLayer();

[jamesr, 2013/02/26 20:48:46]

I can't find any uses of this local in this function

[wjmaclean, 2013/03/01 15:30:32]

Ooops, deleted this, but must have inadvertently restored it in the editor.

+
+    m_pinchZoomScrollbarHorizontal->setBounds(gfx::Size(size.width() - trackWidth, trackWidth));
+    m_pinchZoomScrollbarHorizontal->setPosition(gfx::PointF(0, size.height() - trackWidth));
+    m_pinchZoomScrollbarHorizontal->setIsDrawable(true);
+    m_pinchZoomScrollbarHorizontal->setOpacity(0.5);
+    m_pinchZoomScrollbarHorizontal->setNeedsDisplay();

[jamesr, 2013/02/26 20:48:46]

Most of these properties are the same every time, can't you just set them once
at initialization and have that be it?  The only thing that can change is the
bounds/position.  You should set these only when the layout viewport size
changes, not every commit

[wjmaclean, 2013/03/01 15:30:32]

Fixed.

+
+    m_pinchZoomScrollbarVertical->setBounds(gfx::Size(10, size.height() - 10));

[jamesr, 2013/02/26 20:48:46]

What are these "10"s for?  Are they supposed to be trackWidth or some other
magical value?  If the latter, please put them in a constant with a descriptive
name

[wjmaclean, 2013/03/01 15:30:32]

Fixed.

Trackwidth. I had them set correctly for horizontal, but missed them here.

+    m_pinchZoomScrollbarVertical->setPosition(gfx::PointF(size.width() - 10, 0));
+    m_pinchZoomScrollbarVertical->setIsDrawable(true);
+    m_pinchZoomScrollbarVertical->setOpacity(0.5);
+    m_pinchZoomScrollbarVertical->setNeedsDisplay();
+}
+
+static ScrollbarLayer* findScrollLayerScrollbar(Layer* layer, int targetScrollLayerId)
+{
+    if (layer->toScrollbarLayer()) {
+        int scrollLayerId = layer->toScrollbarLayer()->scrollLayerId();
+        if (scrollLayerId == targetScrollLayerId)
+            return layer->toScrollbarLayer();
+    }
+
+    const Layer::LayerList& children = layer->children();
+    for (size_t childIndex = 0; childIndex < children.size(); ++childIndex) {
+        ScrollbarLayer* result =
+            findScrollLayerScrollbar(children[childIndex].get(), targetScrollLayerId);
+        if (result)
+            return result;
+    }
+
+    return 0;
+}
+
+bool LayerTreeHost::rootScrollLayerUsesOverlayScrollbars() const

[jamesr, 2013/02/26 20:48:46]

This function doesn't seem helpful.  The decision over whether to use pinch zoom
scrollbars or not should be up to the embedder, they can set this however they
like.

[wjmaclean, 2013/03/01 15:30:32]

Done.

+{
+    // Use OS-specific defaults for the case where no rootLayer scrollbar is found.
+#if defined(OS_ANDROID)
+    bool usesOverlay = true;
+#else
+    bool usesOverlay = false;
+#endif
+
+    Layer* rootScrollLayer = this->rootScrollLayer();
+    if (!rootScrollLayer)
+        return usesOverlay;
+
+    ScrollbarLayer* rootScrollLayerScrollbar = findScrollLayerScrollbar(m_rootLayer.get(), rootScrollLayer->id());
+
+    if (rootScrollLayerScrollbar)
+        return rootScrollLayerScrollbar->isOverlay();
+    else
+        return usesOverlay;
+}
+
 void LayerTreeHost::willCommit()
 {
     m_client->willCommit();
@@ -354,6 +425,44 @@ void LayerTreeHost::willCommit()
         m_hudLayer->removeFromParent();
         m_hudLayer = 0;
     }
+
+    // Setup pinch-zoom scrollbars if required.
+    if (rootScrollLayer() && !rootScrollLayerUsesOverlayScrollbars()) {

[jamesr, 2013/02/26 20:48:46]

This should check a setting to determine whether to make pinch zoom scrollbars
or not

[wjmaclean, 2013/03/01 15:30:32]

Done.

+        bool needsPropertiesUpdated = false;
+
+        if (!m_pinchZoomScrollbarHorizontal) {

[jamesr, 2013/02/26 20:48:46]

This is way too much code to add to ::willCommit() and the horizontal and
vertical cases are nearly identical.  Please refactor into a helper function or
two.

[wjmaclean, 2013/03/01 15:30:32]

Done.

+            m_pinchZoomScrollbarHorizontal = ScrollbarLayer::create(
+                make_scoped_ptr(
+                    new PinchZoomScrollbar(
+                        WebKit::WebScrollbar::Horizontal, this)).PassAs<WebKit::WebScrollbar>(),
+                make_scoped_ptr(new PinchZoomScrollbarPainter).PassAs<ScrollbarThemePainter>(),
+                make_scoped_ptr(new WebKit::PinchZoomScrollbarGeometry).PassAs<WebKit::WebScrollbarThemeGeometry>(),
+                0);
+            needsPropertiesUpdated = true;
+        }
+
+        DCHECK(m_pinchZoomScrollbarHorizontal);
+        if (!m_pinchZoomScrollbarHorizontal->parent())
+            m_rootLayer->addChild(m_pinchZoomScrollbarHorizontal);
+
+        if (!m_pinchZoomScrollbarVertical) {
+            m_pinchZoomScrollbarVertical = ScrollbarLayer::create(
+                make_scoped_ptr(
+                    new PinchZoomScrollbar(
+                        WebKit::WebScrollbar::Vertical, this)).PassAs<WebKit::WebScrollbar>(),
+                make_scoped_ptr(new PinchZoomScrollbarPainter).PassAs<ScrollbarThemePainter>(),
+                make_scoped_ptr(new WebKit::PinchZoomScrollbarGeometry).PassAs<WebKit::WebScrollbarThemeGeometry>(),
+                0);
+            needsPropertiesUpdated = true;
+        }
+
+        DCHECK(m_pinchZoomScrollbarVertical);
+        if (!m_pinchZoomScrollbarVertical->parent())
+            m_rootLayer->addChild(m_pinchZoomScrollbarVertical);
+
+        if (needsPropertiesUpdated)
+            setPinchZoomScrollbarPropertiesIfNeeded();
+    }
 }
 
 void LayerTreeHost::commitComplete()
@@ -500,6 +609,7 @@ void LayerTreeHost::setViewportSize(const gfx::Size& layoutViewportSize, const g
     m_layoutViewportSize = layoutViewportSize;
     m_deviceViewportSize = deviceViewportSize;
 
+    setPinchZoomScrollbarPropertiesIfNeeded();
     setNeedsCommit();
 }
 
@@ -593,6 +703,11 @@ static Layer* findFirstScrollableLayer(Layer* layer)
     return 0;
 }
 
+Layer* LayerTreeHost::rootScrollLayer() const

[jamesr, 2013/02/26 20:48:46]

I think this function can completely go away

[wjmaclean, 2013/03/01 15:30:32]

It's still used by PinchZoomScrollbar.

+{
+    return findFirstScrollableLayer(m_rootLayer.get());
+}
+
 void LayerTreeHost::updateLayers(Layer* rootLayer, ResourceUpdateQueue& queue)
 {
     TRACE_EVENT0("cc", "LayerTreeHost::updateLayers");