Separate the logic of popup alignment and workarea handling as delegate.

ui/message_center/views/desktop_popup_alignment_delegate.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/message_center/views/desktop_popup_alignment_delegate.h"
+
+#include "ui/gfx/display.h"
+#include "ui/gfx/geometry/rect.h"
+#include "ui/gfx/screen.h"
+#include "ui/message_center/message_center_style.h"
+#include "ui/message_center/views/message_popup_collection.h"
+
+namespace message_center {
+
+DesktopPopupAlignmentDelegate::DesktopPopupAlignmentDelegate()
+    : alignment_(POPUP_ALIGNMENT_BOTTOM | POPUP_ALIGNMENT_RIGHT),
+      display_id_(gfx::Display::kInvalidDisplayID),
+      screen_(NULL) {
+}
+
+DesktopPopupAlignmentDelegate::~DesktopPopupAlignmentDelegate() {
+  if (screen_)
+    screen_->RemoveObserver(this);
+}
+
+void DesktopPopupAlignmentDelegate::StartObserving(gfx::Screen* screen) {
+  if (screen_ || !screen)
+    return;
+
+  screen_ = screen;
+  screen_->AddObserver(this);
+  gfx::Display display = screen_->GetPrimaryDisplay();
+  display_id_ = display.id();
+  RecomputeAlignment(display);
+}
+
+int DesktopPopupAlignmentDelegate::GetToastOriginX(
+    const gfx::Rect& toast_bounds) const {
+  if (IsFromLeft())
+    return work_area_.x() + kMarginBetweenItems;
+  return work_area_.right() - kMarginBetweenItems - toast_bounds.width();
+}
+
+int DesktopPopupAlignmentDelegate::GetBaseLine() const {
+  return IsTopDown()
+      ? work_area_.y() + kMarginBetweenItems
+      : work_area_.bottom() - kMarginBetweenItems;
+}
+
+int DesktopPopupAlignmentDelegate::GetWorkAreaBottom() const {
+  return work_area_.bottom();
+}
+
+bool DesktopPopupAlignmentDelegate::IsTopDown() const {
+  return (alignment_ & POPUP_ALIGNMENT_TOP) != 0;
+}
+
+bool DesktopPopupAlignmentDelegate::IsFromLeft() const {
+  return (alignment_ & POPUP_ALIGNMENT_LEFT) != 0;
+}
+
+void DesktopPopupAlignmentDelegate::RecomputeAlignment(
+    const gfx::Display& display) {
+  if (work_area_ == display.work_area())
+    return;
+
+  work_area_ = display.work_area();
+
+  // If the taskbar is at the top, render notifications top down. Some platforms
+  // like Gnome can have taskbars at top and bottom. In this case it's more
+  // likely that the systray is on the top one.
+  alignment_ = work_area_.y() > display.bounds().y() ? POPUP_ALIGNMENT_TOP
+                                                     : POPUP_ALIGNMENT_BOTTOM;
+
+  // If the taskbar is on the left show the notifications on the left. Otherwise
+  // show it on right since it's very likely that the systray is on the right if
+  // the taskbar is on the top or bottom.
+  // Since on some platforms like Ubuntu Unity there's also a launcher along
+  // with a taskbar (panel), we need to check that there is really nothing at
+  // the top before concluding that the taskbar is at the left.
+  alignment_ |= (work_area_.x() > display.bounds().x() &&
+                 work_area_.y() == display.bounds().y())
+      ? POPUP_ALIGNMENT_LEFT
+      : POPUP_ALIGNMENT_RIGHT;
+}
+
+void DesktopPopupAlignmentDelegate::OnDisplayAdded(
+    const gfx::Display& new_display) {
+}
+
+void DesktopPopupAlignmentDelegate::OnDisplayRemoved(
+    const gfx::Display& old_display) {
+}
+
+void DesktopPopupAlignmentDelegate::OnDisplayMetricsChanged(
+    const gfx::Display& display,
+    uint32_t metrics) {
+  if (display.id() == display_id_) {
+    RecomputeAlignment(display);
+    DoUpdateIfPossible();
+  }
+}
+
+}  // namespace message_center