The Tor Browser: ipc/chromium/src/base/message_pump

ipc/chromium/src/base/message_pump_glib.cc@6474c204b198 (annotated)

ipc/chromium/src/base/message_pump_glib.cc

Wed, 31 Dec 2014 06:09:35 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:09:35 +0100
changeset 0: 6474c204b198
permissions: -rw-r--r--

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

 // Copyright (c) 2008 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 "base/message_pump_glib.h"
 #include <fcntl.h>
 #include <math.h>
 #include <gtk/gtk.h>
 #include <glib.h>
 #include "base/eintr_wrapper.h"
 #include "base/logging.h"
 #include "base/platform_thread.h"
 namespace {
 // We send a byte across a pipe to wakeup the event loop.
 const char kWorkScheduled = '\0';
 // Return a timeout suitable for the glib loop, -1 to block forever,
 // 0 to return right away, or a timeout in milliseconds from now.
 int GetTimeIntervalMilliseconds(const base::TimeTicks& from) {
   if (from.is_null())
     return -1;
   // Be careful here.  TimeDelta has a precision of microseconds, but we want a
   // value in milliseconds.  If there are 5.5ms left, should the delay be 5 or
   // 6?  It should be 6 to avoid executing delayed work too early.
   int delay = static_cast<int>(
       ceil((from - base::TimeTicks::Now()).InMillisecondsF()));
   // If this value is negative, then we need to run delayed work soon.
   return delay < 0 ? 0 : delay;
 }
 // A brief refresher on GLib:
 //     GLib sources have four callbacks: Prepare, Check, Dispatch and Finalize.
 // On each iteration of the GLib pump, it calls each source's Prepare function.
 // This function should return TRUE if it wants GLib to call its Dispatch, and
 // FALSE otherwise.  It can also set a timeout in this case for the next time
 // Prepare should be called again (it may be called sooner).
 //     After the Prepare calls, GLib does a poll to check for events from the
 // system.  File descriptors can be attached to the sources.  The poll may block
 // if none of the Prepare calls returned TRUE.  It will block indefinitely, or
 // by the minimum time returned by a source in Prepare.
 //     After the poll, GLib calls Check for each source that returned FALSE
 // from Prepare.  The return value of Check has the same meaning as for Prepare,
 // making Check a second chance to tell GLib we are ready for Dispatch.
 //     Finally, GLib calls Dispatch for each source that is ready.  If Dispatch
 // returns FALSE, GLib will destroy the source.  Dispatch calls may be recursive
 // (i.e., you can call Run from them), but Prepare and Check cannot.
 //     Finalize is called when the source is destroyed.
 // NOTE: It is common for subsytems to want to process pending events while
 // doing intensive work, for example the flash plugin. They usually use the
 // following pattern (recommended by the GTK docs):
 // while (gtk_events_pending()) {
 //   gtk_main_iteration();
 // }
 //
 // gtk_events_pending just calls g_main_context_pending, which does the
 // following:
 // - Call prepare on all the sources.
 // - Do the poll with a timeout of 0 (not blocking).
 // - Call check on all the sources.
 // - *Does not* call dispatch on the sources.
 // - Return true if any of prepare() or check() returned true.
 //
 // gtk_main_iteration just calls g_main_context_iteration, which does the whole
 // thing, respecting the timeout for the poll (and block, although it is
 // expected not to if gtk_events_pending returned true), and call dispatch.
 //
 // Thus it is important to only return true from prepare or check if we
 // actually have events or work to do. We also need to make sure we keep
 // internal state consistent so that if prepare/check return true when called
 // from gtk_events_pending, they will still return true when called right
 // after, from gtk_main_iteration.
 //
 // For the GLib pump we try to follow the Windows UI pump model:
 // - Whenever we receive a wakeup event or the timer for delayed work expires,
 // we run DoWork and/or DoDelayedWork. That part will also run in the other
 // event pumps.
 // - We also run DoWork, DoDelayedWork, and possibly DoIdleWork in the main
 // loop, around event handling.
 struct WorkSource : public GSource {
   base::MessagePumpForUI* pump;
 };
 gboolean WorkSourcePrepare(GSource* source,
                            gint* timeout_ms) {
   *timeout_ms = static_cast<WorkSource*>(source)->pump->HandlePrepare();
   // We always return FALSE, so that our timeout is honored.  If we were
   // to return TRUE, the timeout would be considered to be 0 and the poll
   // would never block.  Once the poll is finished, Check will be called.
   return FALSE;
 }
 gboolean WorkSourceCheck(GSource* source) {
   // Only return TRUE if Dispatch should be called.
   return static_cast<WorkSource*>(source)->pump->HandleCheck();
 }
 gboolean WorkSourceDispatch(GSource* source,
                             GSourceFunc unused_func,
                             gpointer unused_data) {
   static_cast<WorkSource*>(source)->pump->HandleDispatch();
   // Always return TRUE so our source stays registered.
   return TRUE;
 }
 // I wish these could be const, but g_source_new wants non-const.
 GSourceFuncs WorkSourceFuncs = {
   WorkSourcePrepare,
   WorkSourceCheck,
   WorkSourceDispatch,
   NULL
 };
 }  // namespace
 namespace base {
 MessagePumpForUI::MessagePumpForUI()
     : state_(NULL),
       context_(g_main_context_default()),
       wakeup_gpollfd_(new GPollFD) {
   // Create our wakeup pipe, which is used to flag when work was scheduled.
   int fds[2];
   CHECK(pipe(fds) == 0);
   wakeup_pipe_read_  = fds[0];
   wakeup_pipe_write_ = fds[1];
   wakeup_gpollfd_->fd = wakeup_pipe_read_;
   wakeup_gpollfd_->events = G_IO_IN;
   work_source_ = g_source_new(&WorkSourceFuncs, sizeof(WorkSource));
   static_cast<WorkSource*>(work_source_)->pump = this;
   g_source_add_poll(work_source_, wakeup_gpollfd_.get());
   // Use a low priority so that we let other events in the queue go first.
   g_source_set_priority(work_source_, G_PRIORITY_DEFAULT_IDLE);
   // This is needed to allow Run calls inside Dispatch.
   g_source_set_can_recurse(work_source_, TRUE);
   g_source_attach(work_source_, context_);
   gdk_event_handler_set(&EventDispatcher, this, NULL);
 }
 MessagePumpForUI::~MessagePumpForUI() {
   gdk_event_handler_set(reinterpret_cast<GdkEventFunc>(gtk_main_do_event),
                         this, NULL);
   g_source_destroy(work_source_);
   g_source_unref(work_source_);
   close(wakeup_pipe_read_);
   close(wakeup_pipe_write_);
 }
 void MessagePumpForUI::RunWithDispatcher(Delegate* delegate,
                                          Dispatcher* dispatcher) {
 #ifndef NDEBUG
   // Make sure we only run this on one thread.  GTK only has one message pump
   // so we can only have one UI loop per process.
   static PlatformThreadId thread_id = PlatformThread::CurrentId();
   DCHECK(thread_id == PlatformThread::CurrentId()) <<
       "Running MessagePumpForUI on two different threads; "
       "this is unsupported by GLib!";
 #endif
   RunState state;
   state.delegate = delegate;
   state.dispatcher = dispatcher;
   state.should_quit = false;
   state.run_depth = state_ ? state_->run_depth + 1 : 1;
   state.has_work = false;
   RunState* previous_state = state_;
   state_ = &state;
   // We really only do a single task for each iteration of the loop.  If we
   // have done something, assume there is likely something more to do.  This
   // will mean that we don't block on the message pump until there was nothing
   // more to do.  We also set this to true to make sure not to block on the
   // first iteration of the loop, so RunAllPending() works correctly.
   bool more_work_is_plausible = true;
   // We run our own loop instead of using g_main_loop_quit in one of the
   // callbacks.  This is so we only quit our own loops, and we don't quit
   // nested loops run by others.  TODO(deanm): Is this what we want?
   for (;;) {
     // Don't block if we think we have more work to do.
     bool block = !more_work_is_plausible;
     // g_main_context_iteration returns true if events have been dispatched.
     more_work_is_plausible = g_main_context_iteration(context_, block);
     if (state_->should_quit)
       break;
     more_work_is_plausible |= state_->delegate->DoWork();
     if (state_->should_quit)
       break;
     more_work_is_plausible |=
         state_->delegate->DoDelayedWork(&delayed_work_time_);
     if (state_->should_quit)
       break;
     if (more_work_is_plausible)
       continue;
     more_work_is_plausible = state_->delegate->DoIdleWork();
     if (state_->should_quit)
       break;
   }
   state_ = previous_state;
 }
 // Return the timeout we want passed to poll.
 int MessagePumpForUI::HandlePrepare() {
   // We know we have work, but we haven't called HandleDispatch yet. Don't let
   // the pump block so that we can do some processing.
   if (state_ &&  // state_ may be null during tests.
       state_->has_work)
     return 0;
   // We don't think we have work to do, but make sure not to block
   // longer than the next time we need to run delayed work.
   return GetTimeIntervalMilliseconds(delayed_work_time_);
 }
 bool MessagePumpForUI::HandleCheck() {
   if (!state_)  // state_ may be null during tests.
     return false;
   // We should only ever have a single message on the wakeup pipe, since we
   // are only signaled when the queue went from empty to non-empty.  The glib
   // poll will tell us whether there was data, so this read shouldn't block.
   if (wakeup_gpollfd_->revents & G_IO_IN) {
     char msg;
     if (HANDLE_EINTR(read(wakeup_pipe_read_, &msg, 1)) != 1 || msg != '!') {
       NOTREACHED() << "Error reading from the wakeup pipe.";
     }
     // Since we ate the message, we need to record that we have more work,
     // because HandleCheck() may be called without HandleDispatch being called
     // afterwards.
     state_->has_work = true;
   }
   if (state_->has_work)
     return true;
   if (GetTimeIntervalMilliseconds(delayed_work_time_) == 0) {
     // The timer has expired. That condition will stay true until we process
     // that delayed work, so we don't need to record this differently.
     return true;
   }
   return false;
 }
 void MessagePumpForUI::HandleDispatch() {
   state_->has_work = false;
   if (state_->delegate->DoWork()) {
     // NOTE: on Windows at this point we would call ScheduleWork (see
     // MessagePumpForUI::HandleWorkMessage in message_pump_win.cc). But here,
     // instead of posting a message on the wakeup pipe, we can avoid the
     // syscalls and just signal that we have more work.
     state_->has_work = true;
   }
   if (state_->should_quit)
     return;
   state_->delegate->DoDelayedWork(&delayed_work_time_);
 }
 void MessagePumpForUI::AddObserver(Observer* observer) {
   observers_.AddObserver(observer);
 }
 void MessagePumpForUI::RemoveObserver(Observer* observer) {
   observers_.RemoveObserver(observer);
 }
 void MessagePumpForUI::WillProcessEvent(GdkEvent* event) {
   FOR_EACH_OBSERVER(Observer, observers_, WillProcessEvent(event));
 }
 void MessagePumpForUI::DidProcessEvent(GdkEvent* event) {
   FOR_EACH_OBSERVER(Observer, observers_, DidProcessEvent(event));
 }
 void MessagePumpForUI::Quit() {
   if (state_) {
     state_->should_quit = true;
   } else {
     NOTREACHED() << "Quit called outside Run!";
   }
 }
 void MessagePumpForUI::ScheduleWork() {
   // This can be called on any thread, so we don't want to touch any state
   // variables as we would then need locks all over.  This ensures that if
   // we are sleeping in a poll that we will wake up.
   char msg = '!';
   if (HANDLE_EINTR(write(wakeup_pipe_write_, &msg, 1)) != 1) {
     NOTREACHED() << "Could not write to the UI message loop wakeup pipe!";
   }
 }
 void MessagePumpForUI::ScheduleDelayedWork(const TimeTicks& delayed_work_time) {
   // We need to wake up the loop in case the poll timeout needs to be
   // adjusted.  This will cause us to try to do work, but that's ok.
   delayed_work_time_ = delayed_work_time;
   ScheduleWork();
 }
 // static
 void MessagePumpForUI::EventDispatcher(GdkEvent* event, gpointer data) {
   MessagePumpForUI* message_pump = reinterpret_cast<MessagePumpForUI*>(data);
   message_pump->WillProcessEvent(event);
   if (message_pump->state_ &&  // state_ may be null during tests.
       message_pump->state_->dispatcher) {
     if (!message_pump->state_->dispatcher->Dispatch(event))
       message_pump->state_->should_quit = true;
   } else {
     gtk_main_do_event(event);
   }
   message_pump->DidProcessEvent(event);
 }
 }  // namespace base

The Tor Browser / annotate

ipc/chromium/src/base/message_pump_glib.cc@6474c204b198 (annotated)

ipc/chromium/src/base/message_pump_glib.cc