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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+// 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 {
+
+// 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),
+ pipe_full_(false) {
+ // 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 only
+ // write to the pipe when pipe_full_ is false. The glib poll will tell us
+ // whether there was data, so this read shouldn't block.
+ if (wakeup_gpollfd_->revents & G_IO_IN) {
+ pipe_full_ = false;
+
+ 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() {
+ bool was_full = pipe_full_.exchange(true);
+ if (was_full) {
+ return;
+ }
+
+ // 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