Chromium compositor change implementing page-scale driven pinch-zoom.

content/renderer/render_view_impl.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/renderer/render_view_impl.h"
 
 #include <algorithm>
 #include <cmath>
 #include <string>
 #include <vector>
@@ skipping 3133 matching lines @@
   return navigation_state;
 }
 
 void RenderViewImpl::ProcessViewLayoutFlags(const CommandLine& command_line) {
   bool enable_viewport =
       command_line.HasSwitch(switches::kEnableViewport);
   bool enable_fixed_layout =
       command_line.HasSwitch(switches::kEnableFixedLayout);
   bool enable_pinch = enable_viewport ||
                       command_line.HasSwitch(switches::kEnablePinch);
+  bool enable_pinch_in_compositor =
+      command_line.HasSwitch(switches::kEnablePinchInCompositor);
 
   webview()->enableFixedLayoutMode(enable_fixed_layout || enable_viewport);
   webview()->settings()->setFixedElementsLayoutRelativeToFrame(true);
   if (!enable_pinch &&
       webview()->isAcceleratedCompositingActive() &&
       webkit_preferences_.apply_default_device_scale_factor_in_compositor &&
       device_scale_factor_ != 1) {
     // Page scaling is disabled by default when applying a scale factor in the
     // compositor since they are currently incompatible.
     webview()->setPageScaleFactorLimits(1, 1);
   }
 
+  if (enable_pinch_in_compositor &&
+      webview()->isAcceleratedCompositingActive())
+    webview()->setPageScaleFactorLimits(1, 4);

[piman, 2012/10/05 00:01:08]

note: this is possibly racy. isAcceleratedCompositingActive() may not be true
now, but could change later. Should we do this as well on
didActivateCompositor()?

[Jeff Timanus, 2012/10/05 00:05:34]

If this is racey, are the other conditions also racey?  They are also gated on
isAccelratedCompositingActive().

[piman, 2012/10/05 00:25:51]

Most likely, yes.

[Jeff Timanus, 2012/10/05 15:37:50]

I'm not sure if fixing these races is appropriate for this change.  I've already
touched a lot of files here.  I think filing a bug and a follow-up change would
be better.  Agree?

+
   if (enable_viewport) {
     webview()->settings()->setViewportEnabled(true);
   } else if (enable_fixed_layout) {
     std::string str =
         command_line.GetSwitchValueASCII(switches::kEnableFixedLayout);
     std::vector<std::string> tokens;
     base::SplitString(str, ',', &tokens);
     if (tokens.size() == 2) {
       int width, height;
       if (base::StringToInt(tokens[0], &width) &&
@@ skipping 3149 matching lines @@
 
   updating_frame_tree_ = true;
   active_frame_id_map_.clear();
 
   target_process_id_ = process_id;
   target_routing_id_ = route_id;
   CreateFrameTree(webview()->mainFrame(), frames);
 
   updating_frame_tree_ = false;
 }