mac: Make dynamic DPI changes work.

This fixes the software case completely, and makes everything
look good on the hardware path after a few frames. In the
hardware path, the IOSurfaces aren't tagged with their own DPI,
so they are rendered at the wrong scale for a few frames, until
the "DPI changed" message made it from the browser to the
renderer.

This CL adds three things that happen in response to DPI changes:
1.) It reallocates the browser-side BackingStoreMac at the new DPI.
2.) It lets the renderer do a full repaint after DPI changed.
3.) It passes the new DPI on to WebKit (in render_view_impl.cc)

(3) won't have an effect for hardware pages until
https://bugs.webkit.org/show_bug.cgi?id=88916 lands.

BUG=128267
TEST=change from lodpi and hidpi and back, check that software- and
hardware-rendered pages look good after the change in both foreground
and background tabs.

Review URL: https://chromiumcodereview.appspot.com/10548026

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@142099 0039d316-1c4b-4281-b951-d872f2087c98

7 files changed, 72 insertions, 9 deletions

diff --git a/content/browser/renderer_host/backing_store_mac.h b/content/browser/renderer_host/backing_store_mac.h
index 17f3e2f..4037071 100644
--- a/content/browser/renderer_host/backing_store_mac.h
+++ b/content/browser/renderer_host/backing_store_mac.h
@@ -27,6 +27,9 @@ class BackingStoreMac : public BackingStore {
   // corresponding Cocoa view has not been inserted into an NSWindow yet.
   CGContextRef cg_bitmap() { return cg_bitmap_; }
 
+  // Called when the view's backing scale factor changes.
+  void ScaleFactorChanged(float device_scale_factor);
+
   // BackingStore implementation.
   virtual size_t MemorySize() OVERRIDE;
   virtual void PaintToBackingStore(
diff --git a/content/browser/renderer_host/backing_store_mac.mm b/content/browser/renderer_host/backing_store_mac.mm
index 326e0d4..ebc0c0d 100644
--- a/content/browser/renderer_host/backing_store_mac.mm
+++ b/content/browser/renderer_host/backing_store_mac.mm
@@ -41,6 +41,28 @@ BackingStoreMac::BackingStoreMac(content::RenderWidgetHost* widget,
 BackingStoreMac::~BackingStoreMac() {
 }
 
+void BackingStoreMac::ScaleFactorChanged(float device_scale_factor) {
+  if (device_scale_factor == device_scale_factor_)
+    return;
+
+  device_scale_factor_ = device_scale_factor;
+
+  base::mac::ScopedCFTypeRef<CGLayerRef> new_layer(CreateCGLayer());
+  // If we have a layer, copy the old contents. A pixelated flash is better
+  // than a white flash.
+  if (new_layer && cg_layer_) {
+    CGContextRef layer = CGLayerGetContext(new_layer);
+    CGContextDrawLayerAtPoint(layer, CGPointMake(0, 0), cg_layer_);
+  }
+
+  cg_layer_.swap(new_layer);
+  if (!cg_layer_) {
+    // The view isn't in a window yet.  Use a CGBitmapContext for now.
+    cg_bitmap_.reset(CreateCGBitmapContext());
+    CGContextScaleCTM(cg_bitmap_, device_scale_factor_, device_scale_factor_);
+  }
+}
+
 size_t BackingStoreMac::MemorySize() {
   return size().Scale(device_scale_factor_).GetArea() * 4;
 }
diff --git a/content/browser/renderer_host/render_widget_host_view_mac.mm b/content/browser/renderer_host/render_widget_host_view_mac.mm
index 7a95ba3..d0e675c 100644
--- a/content/browser/renderer_host/render_widget_host_view_mac.mm
+++ b/content/browser/renderer_host/render_widget_host_view_mac.mm
@@ -159,6 +159,7 @@ float ScaleFactor(NSView* view) {
 - (void)cancelChildPopups;
 - (void)windowDidChangeBackingProperties:(NSNotification*)notification;
 - (void)checkForPluginImeCancellation;
+- (void)updateTabBackingStoreScaleFactor;
 @end
 
 // NSEvent subtype for scroll gestures events.
@@ -399,6 +400,10 @@ void RenderWidgetHostViewMac::DidBecomeSelected() {
   if (!is_hidden_)
     return;
 
+  // Check if the backing scale factor changed while the tab was in the
+  // background.
+  [cocoa_view_ updateTabBackingStoreScaleFactor];
+
   if (web_contents_switch_paint_time_.is_null())
     web_contents_switch_paint_time_ = base::TimeTicks::Now();
   is_hidden_ = false;
@@ -820,8 +825,6 @@ bool RenderWidgetHostViewMac::IsPopup() const {
 
 BackingStore* RenderWidgetHostViewMac::AllocBackingStore(
     const gfx::Size& size) {
-  // TODO(thakis): Register for backing scale factor change events and pass
-  // that on.
   float scale = ScaleFactor(cocoa_view_);
   return new BackingStoreMac(render_widget_host_, size, scale);
 }
@@ -1890,6 +1893,20 @@ void RenderWidgetHostViewMac::SetTextInputActive(bool active) {
   }
 }
 
+- (void)updateTabBackingStoreScaleFactor {
+  if (!renderWidgetHostView_->render_widget_host_)
+    return;
+
+  float scaleFactor = ScaleFactor(self);
+  BackingStoreMac* backingStore = static_cast<BackingStoreMac*>(
+      renderWidgetHostView_->render_widget_host_->GetBackingStore(false));
+  if (backingStore)  // NULL in hardware path.
+    backingStore->ScaleFactorChanged(scaleFactor);
+
+  renderWidgetHostView_->render_widget_host_->SetDeviceScaleFactor(
+      scaleFactor);
+}
+
 // http://developer.apple.com/library/mac/#documentation/GraphicsAnimation/Conceptual/HighResolutionOSX/CapturingScreenContents/CapturingScreenContents.html#//apple_ref/doc/uid/TP40012302-CH10-SW4
 - (void)windowDidChangeBackingProperties:(NSNotification*)notification {
   NSWindow* window = (NSWindow*)[notification object];
@@ -1899,11 +1916,16 @@ void RenderWidgetHostViewMac::SetTextInputActive(bool active) {
       [[notification userInfo] objectForKey:NSBackingPropertyOldScaleFactorKey])
       doubleValue];
   if (newBackingScaleFactor != oldBackingScaleFactor) {
-    // TODO(thakis): Tell backing store about new DPI, schedule repaint.
-    if (renderWidgetHostView_->render_widget_host_) {
-      renderWidgetHostView_->render_widget_host_->SetDeviceScaleFactor(
-          newBackingScaleFactor);
-    }
+    // Background tabs check if their scale factor changed when they become
+    // active, in DidBecomeSelected().
+
+    // Allocating a CGLayerRef with the current scale factor immediately from
+    // this handler doesn't work. Schedule the backing store update on the
+    // next runloop cycle, then things are read for CGLayerRef allocations to
+    // work.
+    [self performSelector:@selector(updateTabBackingStoreScaleFactor)
+               withObject:nil
+               afterDelay:0];
   }
 }
 
diff --git a/content/renderer/render_view_impl.cc b/content/renderer/render_view_impl.cc
index 3882d2f..3d29c1d 100644
--- a/content/renderer/render_view_impl.cc
+++ b/content/renderer/render_view_impl.cc
@@ -5329,6 +5329,12 @@ void RenderViewImpl::OnImeConfirmComposition(
   }
 }
 
+void RenderViewImpl::OnSetDeviceScaleFactor(float device_scale_factor) {
+  RenderWidget::OnSetDeviceScaleFactor(device_scale_factor);
+  if (webview())
+    webview()->setDeviceScaleFactor(device_scale_factor);
+}
+
 ui::TextInputType RenderViewImpl::GetTextInputType() {
   return pepper_delegate_.IsPluginFocused() ?
       pepper_delegate_.GetTextInputType() : RenderWidget::GetTextInputType();
diff --git a/content/renderer/render_view_impl.h b/content/renderer/render_view_impl.h
index 62559f43..f240194 100644
--- a/content/renderer/render_view_impl.h
+++ b/content/renderer/render_view_impl.h
@@ -753,6 +753,7 @@ class RenderViewImpl : public RenderWidget,
       int selection_end) OVERRIDE;
   virtual void OnImeConfirmComposition(
       const string16& text, const ui::Range& replacement_range) OVERRIDE;
+  virtual void OnSetDeviceScaleFactor(float device_scale_factor) OVERRIDE;
   virtual ui::TextInputType GetTextInputType() OVERRIDE;
   virtual void GetSelectionBounds(gfx::Rect* start, gfx::Rect* end) OVERRIDE;
   virtual void GetCompositionCharacterBounds(
diff --git a/content/renderer/render_widget.cc b/content/renderer/render_widget.cc
index af69bf1..12cad67 100644
--- a/content/renderer/render_widget.cc
+++ b/content/renderer/render_widget.cc
@@ -1490,7 +1490,16 @@ void RenderWidget::OnMsgRepaint(const gfx::Size& size_to_paint) {
 }
 
 void RenderWidget::OnSetDeviceScaleFactor(float device_scale_factor) {
-  // TODO(thakis): Set device_scale_factor_, possibly trigger a repaint.
+  if (device_scale_factor_ == device_scale_factor)
+    return;
+
+  device_scale_factor_ = device_scale_factor;
+
+  if (!is_accelerated_compositing_active_) {
+    didInvalidateRect(gfx::Rect(size_.width(), size_.height()));
+  } else {
+    scheduleComposite();
+  }
 }
 
 void RenderWidget::OnSetTextDirection(WebTextDirection direction) {
diff --git a/content/renderer/render_widget.h b/content/renderer/render_widget.h
index 5b6d07f..6411374 100644
--- a/content/renderer/render_widget.h
+++ b/content/renderer/render_widget.h
@@ -254,7 +254,7 @@ class CONTENT_EXPORT RenderWidget
                         const gfx::Size& page_size,
                         const gfx::Size& desired_size);
   void OnMsgRepaint(const gfx::Size& size_to_paint);
-  void OnSetDeviceScaleFactor(float device_scale_factor);
+  virtual void OnSetDeviceScaleFactor(float device_scale_factor);
   void OnSetTextDirection(WebKit::WebTextDirection direction);
   void OnGetFPS();