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 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */

 /* This Source Code Form is subject to the terms of the Mozilla Public

  * License, v. 2.0. If a copy of the MPL was not distributed with this

  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

 // Use "dyld interposing" to hook methods imported from other libraries in the

 // plugin child process.  The basic technique is described at

 // http://books.google.com/books?id=K8vUkpOXhN4C&pg=PA73&lpg=PA73&dq=__interpose&source=bl&ots=OJnnXZYpZC&sig=o7I3lXvoduUi13SrPfOON7o3do4&hl=en&ei=AoehS9brCYGQNrvsmeUM&sa=X&oi=book_result&ct=result&resnum=6&ved=0CBsQ6AEwBQ#v=onepage&q=__interpose&f=false.

 // The idea of doing it for the plugin child process comes from Chromium code,

 // particularly from plugin_carbon_interpose_mac.cc

 // (http://codesearch.google.com/codesearch/p?hl=en#OAMlx_jo-ck/src/chrome/browser/plugin_carbon_interpose_mac.cc&q=nscursor&exact_package=chromium&d=1&l=168)

 // and from PluginProcessHost::Init() in plugin_process_host.cc

 // (http://codesearch.google.com/codesearch/p?hl=en#OAMlx_jo-ck/src/content/browser/plugin_process_host.cc&q=nscursor&exact_package=chromium&d=1&l=222).

 // These hooks are needed to make certain OS calls work from the child process

 // (a background process) that would normally only work when called in the

 // parent process (the foreground process).  They allow us to serialize

 // information from the child process to the parent process, so that the same

 // (or equivalent) calls can be made from the parent process.

 // This file lives in a seperate module (libplugin_child_interpose.dylib),

 // which will get loaded by the OS before any other modules when the plugin

 // child process is launched (from GeckoChildProcessHost::

 // PerformAsyncLaunchInternal()).  For this reason it shouldn't link in other

 // browser modules when loaded.  Instead it should use dlsym() to load

 // pointers to the methods it wants to call in other modules.

 #if !defined(__LP64__)

 #include <dlfcn.h>

 #import <Carbon/Carbon.h>

 // The header file QuickdrawAPI.h is missing on OS X 10.7 and up (though the

 // QuickDraw APIs defined in it are still present) -- so we need to supply the

 // relevant parts of its contents here.  It's likely that Apple will eventually

 // remove the APIs themselves (probably in OS X 10.8), so we need to make them

 // weak imports, and test for their presence before using them.

 #if !defined(__QUICKDRAWAPI__)

 struct Cursor;

 extern "C" void SetCursor(const Cursor * crsr) __attribute__((weak_import));

 #endif /* __QUICKDRAWAPI__ */

 BOOL (*OnSetThemeCursorPtr) (ThemeCursor) = NULL;

 BOOL (*OnSetCursorPtr) (const Cursor*) = NULL;

 BOOL (*OnHideCursorPtr) () = NULL;

 BOOL (*OnShowCursorPtr) () = NULL;

 static BOOL loadXULPtrs()

 {

   if (!OnSetThemeCursorPtr) {

     // mac_plugin_interposing_child_OnSetThemeCursor(ThemeCursor cursor) is in

     // PluginInterposeOSX.mm

     OnSetThemeCursorPtr = (BOOL(*)(ThemeCursor))

       dlsym(RTLD_DEFAULT, "mac_plugin_interposing_child_OnSetThemeCursor");

   }

   if (!OnSetCursorPtr) {

     // mac_plugin_interposing_child_OnSetCursor(const Cursor* cursor) is in

     // PluginInterposeOSX.mm

     OnSetCursorPtr = (BOOL(*)(const Cursor*))

       dlsym(RTLD_DEFAULT, "mac_plugin_interposing_child_OnSetCursor");

   }

   if (!OnHideCursorPtr) {

     // mac_plugin_interposing_child_OnHideCursor() is in PluginInterposeOSX.mm

     OnHideCursorPtr = (BOOL(*)())

       dlsym(RTLD_DEFAULT, "mac_plugin_interposing_child_OnHideCursor");

   }

   if (!OnShowCursorPtr) {

     // mac_plugin_interposing_child_OnShowCursor() is in PluginInterposeOSX.mm

     OnShowCursorPtr = (BOOL(*)())

       dlsym(RTLD_DEFAULT, "mac_plugin_interposing_child_OnShowCursor");

   }

   return (OnSetCursorPtr && OnSetThemeCursorPtr && OnHideCursorPtr && OnShowCursorPtr);

 }

 static OSStatus MacPluginChildSetThemeCursor(ThemeCursor cursor)

 {

   if (loadXULPtrs()) {

     OnSetThemeCursorPtr(cursor);

   }

   return ::SetThemeCursor(cursor);

 }

 static void MacPluginChildSetCursor(const Cursor* cursor)

 {

   if (::SetCursor) {

     if (loadXULPtrs()) {

       OnSetCursorPtr(cursor);

     }

     ::SetCursor(cursor);

   }

 }

 static CGError MacPluginChildCGDisplayHideCursor(CGDirectDisplayID display)

 {

   if (loadXULPtrs()) {

     OnHideCursorPtr();

   }

   return ::CGDisplayHideCursor(display);

 }

 static CGError MacPluginChildCGDisplayShowCursor(CGDirectDisplayID display)

 {

   if (loadXULPtrs()) {

     OnShowCursorPtr();

   }

   return ::CGDisplayShowCursor(display);

 }

 #pragma mark -

 struct interpose_substitution {

   const void* replacement;

   const void* original;

 };

 #define INTERPOSE_FUNCTION(function) \

     { reinterpret_cast<const void*>(MacPluginChild##function), \

       reinterpret_cast<const void*>(function) }

 __attribute__((used)) static const interpose_substitution substitutions[]

     __attribute__((section("__DATA, __interpose"))) = {

   INTERPOSE_FUNCTION(SetThemeCursor),

   INTERPOSE_FUNCTION(CGDisplayHideCursor),

   INTERPOSE_FUNCTION(CGDisplayShowCursor),

   // SetCursor() and other QuickDraw APIs will probably be removed in OS X

   // 10.8.  But this will make 'SetCursor' NULL, which will just stop the OS

   // from interposing it (tested using an INTERPOSE_FUNCTION_BROKEN macro

   // that just sets the second address of each tuple to NULL).

   INTERPOSE_FUNCTION(SetCursor),

 };

 #endif  // !__LP64__