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

--1:000000000000
+:0d2596ddb77e
+// 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

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comparison: ipc/chromium/src/base/message_pump_glib.cc

ipc/chromium/src/base/message_pump_glib.cc