linux: Pass subpixel positioning setting to WebKit.

content/browser/renderer_host/render_sandbox_host_linux.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/browser/renderer_host/render_sandbox_host_linux.h"
 
 #include <fcntl.h>
 #include <fontconfig/fontconfig.h>
 #include <stdint.h>
 #include <unistd.h>
@@ skipping 16 matching lines @@
 #include "base/shared_memory.h"
 #include "base/string_number_conversions.h"
 #include "base/string_util.h"
 #include "content/common/font_config_ipc_linux.h"
 #include "content/common/sandbox_methods_linux.h"
 #include "content/common/webkitplatformsupport_impl.h"
 #include "skia/ext/SkFontHost_fontconfig_direct.h"
 #include "third_party/npapi/bindings/npapi_extensions.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebKit.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/linux/WebFontInfo.h"
+#include "ui/base/ui_base_switches.h"
 
 using WebKit::WebCString;
 using WebKit::WebFontInfo;
 using WebKit::WebUChar;
 
 // http://code.google.com/p/chromium/wiki/LinuxSandboxIPC
 
 // BEWARE: code in this file run across *processes* (not just threads).
 
 // This code runs in a child process
 class SandboxIPCProcess  {
  public:
   // lifeline_fd: this is the read end of a pipe which the browser process
   //   holds the other end of. If the browser process dies, its descriptors are
   //   closed and we will noticed an EOF on the pipe. That's our signal to exit.
   // browser_socket: the browser's end of the sandbox IPC socketpair. From the
   //   point of view of the renderer, it's talking to the browser but this
   //   object actually services the requests.
   // sandbox_cmd: the path of the sandbox executable
   SandboxIPCProcess(int lifeline_fd, int browser_socket,
                     std::string sandbox_cmd)
       : lifeline_fd_(lifeline_fd),
         browser_socket_(browser_socket),
         font_config_(new FontConfigDirect()) {
     if (!sandbox_cmd.empty()) {
       sandbox_cmd_.push_back(sandbox_cmd);
       sandbox_cmd_.push_back(base::kFindInodeSwitch);
     }
+
+    // FontConfig doesn't provide a standard property to control subpixel
+    // positioning, so we pass a UI flag through to WebKit.
+    WebFontInfo::setSubpixelPositioning(
+        CommandLine::ForCurrentProcess()->HasSwitch(
+            switches::kEnableTextSubpixelPositioning));

[tony, 2012/06/06 23:43:16]

How does this command line switch get set on the sandbox IPC process?

[Daniel Erat, 2012/06/07 00:13:34]

That's a good question (for Adam). :-)  It seems to work.  Markus wasn't sure
where this code is running when I asked him.

[agl, 2012/06/07 21:55:24]

I have no idea either. How does this even compile? There's no 
setSubpixelPositioning function added in this CL. Is it a WebKit change?

(After syncing WebKit)

Ok, I see it. Yea, seems like it should work.

   }
 
   ~SandboxIPCProcess();
 
   void Run() {
     struct pollfd pfds[2];
     pfds[0].fd = lifeline_fd_;
     pfds[0].events = POLLIN;
     pfds[1].fd = browser_socket_;
     pfds[1].events = POLLIN;
@@ skipping 218 matching lines @@
     EnsureWebKitInitialized();
     WebKit::WebFontRenderStyle style;
     WebFontInfo::renderStyleForStrike(family.c_str(), sizeAndStyle, &style);
 
     Pickle reply;
     reply.WriteInt(style.useBitmaps);
     reply.WriteInt(style.useAutoHint);
     reply.WriteInt(style.useHinting);
     reply.WriteInt(style.hintStyle);
     reply.WriteInt(style.useAntiAlias);
-    reply.WriteInt(style.useSubpixel);
+    reply.WriteInt(style.useSubpixelRendering);
+    reply.WriteInt(style.useSubpixelPositioning);
 
     SendRendererReply(fds, reply, -1);
   }
 
   void HandleLocaltime(int fd, const Pickle& pickle, PickleIterator iter,
                        std::vector<int>& fds) {
     // The other side of this call is in zygote_main_linux.cc
 
     std::string time_string;
     if (!pickle.ReadString(&iter, &time_string) ||
@@ skipping 408 matching lines @@
 }
 
 RenderSandboxHostLinux::~RenderSandboxHostLinux() {
   if (initialized_) {
     if (HANDLE_EINTR(close(renderer_socket_)) < 0)
       PLOG(ERROR) << "close";
     if (HANDLE_EINTR(close(childs_lifeline_fd_)) < 0)
       PLOG(ERROR) << "close";
   }
 }