Zoom Extension API (content changes)

content/common/view_messages.h

 // 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.
 
 // IPC messages for page rendering.
 // Multiply-included message file, hence no include guard.
 
 #include "base/memory/shared_memory.h"
 #include "base/process/process.h"
 #include "base/strings/string16.h"
@@ skipping 662 matching lines @@
 // Set the zoom level for a particular url that the renderer is in the
 // process of loading.  This will be stored, to be used if the load commits
 // and ignored otherwise.
 IPC_MESSAGE_ROUTED2(ViewMsg_SetZoomLevelForLoadingURL,
                     GURL /* url */,
                     double /* zoom_level */)
 
 // Set the zoom level for a particular url, so all render views
 // displaying this url can update their zoom levels to match.
 // If scheme is empty, then only host is used for matching.
-IPC_MESSAGE_CONTROL3(ViewMsg_SetZoomLevelForCurrentURL,
+// Render views in the exception list do not have their levels changed.
+IPC_MESSAGE_CONTROL4(ViewMsg_SetZoomLevelForCurrentURL,
                      std::string /* scheme */,
                      std::string /* host */,
-                     double /* zoom_level */)
+                     double /* zoom_level */,
+                     std::set<int> /* exceptions */)

[Fady Samuel, 2014/06/09 15:43:21]

It seems kind of heavy weight to iterate through and carry an exception level
across processes with every zoom level change. I wonder if it would be more
efficient to store an exception bit in the renderer and update that bit through
another IPC.

[wjmaclean, 2014/06/09 17:23:29]

Personally, I would think that a single IPC would be more efficient, since the
majority of the cost would be in setting up the message, and doing the
transmission. That being said, I have never seen performance metrics for this
sort of thing, so I can't be sure.

In most cases I would expect the set to be small or even empty.

The cost of the iteration is immaterial, as iterating over the temporary zoom
levels list in HostZoomMap should be small, we'd still have to do the iteration
in RenderThreadImpl.

If we *did* go this route, then I would suggest staying with the IPC below, but
knowing that once this is called on a render view that it automatically puts
itself into "temporary" mode, and RenderThreadImpl checks the status of each
view before trying to call SetZoomLevel on it. There would need to be another
IPC to reset the view though.

+
+// Set the zoom level for a particular render view.
+IPC_MESSAGE_ROUTED1(ViewMsg_SetZoomLevelForView,

[Fady Samuel, 2014/06/09 15:43:21]

To the comment above, the first parameter sets the exception bit, and the second
sets the zoom level.

ViewMsg_SetTemporaryZoomLevel(bool /* enabled */,
                              double /* level */)

+                    double /* zoom_level */)
 
 // Change encoding of page in the renderer.
 IPC_MESSAGE_ROUTED1(ViewMsg_SetPageEncoding,
                     std::string /*new encoding name*/)
 
 // Reset encoding of page in the renderer back to default.
 IPC_MESSAGE_ROUTED0(ViewMsg_ResetPageEncodingToDefault)
 
 // Used to tell a render view whether it should expose various bindings
 // that allow JS content extended privileges.  See BindingsPolicy for valid
@@ skipping 1026 matching lines @@
 // synchronously (see crbug.com/120597). This IPC message sends the character
 // bounds after every composition change to always have correct bound info.
 IPC_MESSAGE_ROUTED2(ViewHostMsg_ImeCompositionRangeChanged,
                     gfx::Range /* composition range */,
                     std::vector<gfx::Rect> /* character bounds */)
 #endif
 
 // Adding a new message? Stick to the sort order above: first platform
 // independent ViewMsg, then ifdefs for platform specific ViewMsg, then platform
 // independent ViewHostMsg, then ifdefs for platform specific ViewHostMsg.