x11: Make the event-source work with both glib and libevent message-pumps.

ui/events/platform/x11/x11_event_source_glib.cc

+// Copyright 2014 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 "ui/events/platform/x11/x11_event_source.h"
+
+#include <glib.h>
+#include <X11/Xlib.h>
+
+namespace ui {
+
+namespace {
+
+struct GLibX11Source : public GSource {
+  // Note: The GLibX11Source is created and destroyed by GLib. So its
+  // constructor/destructor may or may not get called.
+  XDisplay* display;
+  GPollFD* poll_fd;
+};
+
+gboolean XSourcePrepare(GSource* source, gint* timeout_ms) {
+  GLibX11Source* gxsource = static_cast<GLibX11Source*>(source);
+  if (XPending(gxsource->display))
+    *timeout_ms = 0;
+  else
+    *timeout_ms = -1;
+  return FALSE;
+}
+
+gboolean XSourceCheck(GSource* source) {
+  GLibX11Source* gxsource = static_cast<GLibX11Source*>(source);
+  return XPending(gxsource->display);
+}
+
+gboolean XSourceDispatch(GSource* source,
+                         GSourceFunc unused_func,
+                         gpointer data) {
+  X11EventSource* x11_source = static_cast<X11EventSource*>(data);
+  x11_source->DispatchXEvents();
+  return TRUE;
+}
+
+GSourceFuncs XSourceFuncs = {
+  XSourcePrepare,
+  XSourceCheck,
+  XSourceDispatch,
+  NULL
+};
+
+class X11EventSourceGlib : public X11EventSource {
+ public:
+  explicit X11EventSourceGlib(XDisplay* display)
+      : X11EventSource(display),
+        x_source_(NULL) {
+    InitXSource(ConnectionNumber(display));
+  }
+
+  virtual ~X11EventSourceGlib() {
+    g_source_destroy(x_source_);
+    g_source_unref(x_source_);
+  }
+
+ private:
+  void InitXSource(int fd) {
+    CHECK(!x_source_);
+    CHECK(display()) << "Unable to get connection to X server";
+
+    x_poll_.reset(new GPollFD());
+    x_poll_->fd = fd;
+    x_poll_->events = G_IO_IN;
+    x_poll_->revents = 0;
+
+    GLibX11Source* glib_x_source = static_cast<GLibX11Source*>
+        (g_source_new(&XSourceFuncs, sizeof(GLibX11Source)));
+    glib_x_source->display = display();
+    glib_x_source->poll_fd = x_poll_.get();
+
+    x_source_ = glib_x_source;
+    g_source_add_poll(x_source_, x_poll_.get());
+    g_source_set_can_recurse(x_source_, TRUE);
+    g_source_set_callback(x_source_, NULL, this, NULL);
+    g_source_attach(x_source_, g_main_context_default());
+  }
+
+  // The GLib event source for X events.
+  GSource* x_source_;
+
+  // The poll attached to |x_source_|.
+  scoped_ptr<GPollFD> x_poll_;
+
+  DISALLOW_COPY_AND_ASSIGN(X11EventSourceGlib);
+};
+
+}  // namespace
+
+scoped_ptr<PlatformEventSource> PlatformEventSource::CreateDefault() {
+  return scoped_ptr<PlatformEventSource>(
+      new X11EventSourceGlib(gfx::GetXDisplay()));
+}
+
+}  // namespace ui