Refactor X11ForeignWindowManager (Reland)

ui/base/x/x11_window_event_manager.cc

Index: ui/base/x/x11_window_event_manager.cc
diff --git a/ui/base/x/x11_window_event_manager.cc b/ui/base/x/x11_window_event_manager.cc
new file mode 100644
index 0000000000000000000000000000000000000000..c91fc29f834aef093f385a0b83d6db375145f5a1
--- /dev/null
+++ b/ui/base/x/x11_window_event_manager.cc
@@ -0,0 +1,104 @@
+// 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/base/x/x11_window_event_manager.h"
+
+#include <stddef.h>
+#include <X11/Xlib.h>
+#include <X11/Xlib-xcb.h>
+#include <xcb/xcb.h>
+
+#include "base/compiler_specific.h"
+#include "base/memory/singleton.h"
+
+namespace ui {
+
+// static
+XWindowEventManager* XWindowEventManager::GetInstance() {
+  return base::Singleton<XWindowEventManager>::get();
+}
+
+void XWindowEventManager::SelectEvents(XID xid, uint32_t event_mask) {
+  BeforeMaskChanged(xid);
+  MultiMask& mask = mask_map_[xid];
+  mask.AddMask(event_mask);
+  AfterMaskChanged(xid);
+}
+
+void XWindowEventManager::DeselectEvents(XID xid, uint32_t event_mask) {
+  DCHECK(mask_map_.find(xid) != mask_map_.end());
+  BeforeMaskChanged(xid);
+  MultiMask& mask = mask_map_[xid];
+  mask.RemoveMask(event_mask);
+  AfterMaskChanged(xid);
+}
+
+XWindowEventManager::XWindowEventManager() {}
+XWindowEventManager::~XWindowEventManager() {}
+
+void XWindowEventManager::BeforeMaskChanged(XID xid) {
+  old_mask_ = mask_map_[xid].ToMask();

[Daniel Erat, 2016/09/07 00:37:33]

caching this in a single member feels a bit scary. why not just copy it to a
local in SelectEvents and DeselectEvents and then pass the old mask to
AfterMaskChanged?

[Tom (Use chromium acct), 2016/09/07 18:02:22]

Done.

+}
+
+void XWindowEventManager::AfterMaskChanged(XID xid) {
+  uint32_t new_mask = mask_map_[xid].ToMask();
+  if (new_mask == old_mask_)
+    return;
+
+  XDisplay* display = gfx::GetXDisplay();
+  xcb_connection_t* connection = XGetXCBConnection(display);
+  auto cookie = xcb_change_window_attributes(connection, xid, XCB_CW_EVENT_MASK,
+                                             &new_mask);
+  // Window |xid| may already be destroyed at this point, so the
+  // change_attributes request may give a BadWindow error.  In this case, just
+  // ignore the error.
+  xcb_discard_reply(connection, cookie.sequence);
+
+  if (new_mask == NoEventMask)
+    mask_map_.erase(xid);
+}
+
+XWindowEventManager::ScopedEventSelector::ScopedEventSelector(
+    XID xid,
+    uint32_t event_mask)
+    : xid_(xid), event_mask_(event_mask) {
+  XWindowEventManager::GetInstance()->SelectEvents(xid_, event_mask_);
+}
+
+XWindowEventManager::ScopedEventSelector::~ScopedEventSelector() {
+  XWindowEventManager::GetInstance()->DeselectEvents(xid_, event_mask_);
+}
+
+XWindowEventManager::MultiMask::MultiMask() {
+  for (int i = 0; i < kMaskSize; i++)
+    mask_bits[i] = 0;
+}
+
+XWindowEventManager::MultiMask::~MultiMask() {}
+
+void XWindowEventManager::MultiMask::AddMask(uint32_t mask) {
+  for (int i = 0; i < kMaskSize; i++) {
+    if (mask & (1 << i))
+      mask_bits[i]++;
+  }
+}
+
+void XWindowEventManager::MultiMask::RemoveMask(uint32_t mask) {
+  for (int i = 0; i < kMaskSize; i++) {
+    if (mask & (1 << i))
+      DCHECK(mask_bits[i]);
+    mask_bits[i]--;
+  }
+}
+
+uint32_t XWindowEventManager::MultiMask::ToMask() const {
+  uint32_t mask = NoEventMask;
+  for (int i = 0; i < kMaskSize; i++) {
+    if (mask_bits[i])
+      mask |= (1 << i);
+  }
+  return mask;
+}
+
+}  // namespace ui