Support auto-hide taskbar for panels on Windows.

chrome/browser/ui/panels/auto_hide_bottom_bar_win.cc

+// Copyright (c) 2011 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 "chrome/browser/ui/panels/auto_hide_bottom_bar.h"
+
+#include <windows.h>
+#include <shellapi.h>
+
+#include "base/compiler_specific.h"
+#include "base/logging.h"
+#include "base/timer.h"
+#include "ui/gfx/rect.h"
+
+namespace {
+
+// The thickness of the top area of an auto-hide taskbar that is still visible
+// when the taskbar is hidden.
+const int kAutoHideTaskbarThicknessPx = 2;
+
+// The polling interval to check auto-hide taskbar.
+const int kCheckTaskbarPollingIntervalMs = 500;
+
+class AutoHideBottomBarWin : public AutoHideBottomBar {
+ public:
+  explicit AutoHideBottomBarWin(Observer* observer);
+  virtual ~AutoHideBottomBarWin();
+
+  virtual void UpdateWorkArea(const gfx::Rect& work_area) OVERRIDE;
+  virtual bool IsEnabled() OVERRIDE;
+  virtual int GetHeight() OVERRIDE;
+  virtual Visibility GetVisibility() OVERRIDE;
+
+ private:
+  void ValidateAndGetWindow();
+  HWND GetAutoHideWindowOnScreenEdge(UINT edge) const;
+  gfx::Rect GetBounds();
+  int GetHeightFromBounds(const gfx::Rect& bounds) const;
+  Visibility GetVisibilityFromBounds(const gfx::Rect& bounds) const;
+  void CheckTaskbar();
+
+  Observer* observer_;
+  gfx::Rect work_area_;
+  HMONITOR monitor_;
+  HWND window_;
+  bool aligned_to_bottom_;
+  Visibility visibility_;
+  int height_;
+  base::RepeatingTimer<AutoHideBottomBarWin> polling_timer_;
+
+  DISALLOW_COPY_AND_ASSIGN(AutoHideBottomBarWin);
+};
+
+AutoHideBottomBarWin::AutoHideBottomBarWin(Observer* observer)
+    : observer_(observer),
+      window_(NULL),
+      aligned_to_bottom_(false),
+      visibility_(VISIBLE),
+      height_(0) {
+  DCHECK(observer);
+}
+
+AutoHideBottomBarWin::~AutoHideBottomBarWin() {
+}
+
+void AutoHideBottomBarWin::UpdateWorkArea(const gfx::Rect& work_area) {
+  if (work_area_ == work_area)
+    return;
+  work_area_ = work_area;
+
+  RECT rect = work_area_.ToRECT();
+  monitor_ = ::MonitorFromRect(&rect, MONITOR_DEFAULTTOPRIMARY);
+  DCHECK(monitor_);
+
+  ValidateAndGetWindow();
+
+  if (window_) {
+    visibility_ = GetVisibility();
+    height_ = GetHeight();
+
+    if (!polling_timer_.IsRunning()) {
+      polling_timer_.Start(
+          base::TimeDelta::FromMilliseconds(kCheckTaskbarPollingIntervalMs),
+          this,
+          &AutoHideBottomBarWin::CheckTaskbar);
+    }
+  } else {
+    if (polling_timer_.IsRunning())
+      polling_timer_.Stop();
+  }
+}
+
+bool AutoHideBottomBarWin::IsEnabled() {
+  ValidateAndGetWindow();
+  return window_ != NULL && aligned_to_bottom_;
+}
+
+int AutoHideBottomBarWin::GetHeight() {
+  return GetHeightFromBounds(GetBounds());
+}
+
+AutoHideBottomBar::Visibility AutoHideBottomBarWin::GetVisibility() {
+  return GetVisibilityFromBounds(GetBounds());
+}
+
+void AutoHideBottomBarWin::ValidateAndGetWindow() {
+  // Make sure |window_| is still valid since Shell might be restarted.
+  if (window_) {
+    if (::IsWindow(window_)) {
+      // Re-check the edge alignment.
+      aligned_to_bottom_ = window_ == GetAutoHideWindowOnScreenEdge(ABE_BOTTOM);
+      return;
+    }
+
+    window_ = NULL;
+  }
+
+  // Otherwise, find the auto-hide taskbar window that could appear in any edge
+  // of the work area. Note that we have to check all edges because the user
+  // might move the taskbar from non-bottom edge to bottom edge.

[Peter Kasting, 2011/08/23 20:39:18]

Note that it is technically possible to have multiple auto-hide taskbars
simultaneously, on various different screen edges.  Your code should not assume
that there is exactly or at most one such bar.

[jianli, 2011/08/26 00:18:16]

Fixed.

+  UINT edges[] = { ABE_BOTTOM, ABE_RIGHT, ABE_LEFT, ABE_TOP };
+  for (size_t i = 0; i < arraysize(edges); ++i) {
+    window_ = GetAutoHideWindowOnScreenEdge(edges[i]);
+    if (window_) {
+      aligned_to_bottom_ = edges[i] == ABE_BOTTOM;
+      break;
+    }
+  }
+}
+
+HWND AutoHideBottomBarWin::GetAutoHideWindowOnScreenEdge(UINT edge) const {

[Peter Kasting, 2011/08/23 20:39:18]

It looks like this function is almost identical to code in native_widget_win.cc.
 Can you just make that version return an HWND, or find some other way to avoid
having this code two places?

[jianli, 2011/08/26 00:18:16]

Done.

+  APPBARDATA taskbar_data = { 0 };
+  taskbar_data.cbSize = sizeof APPBARDATA;
+  taskbar_data.uEdge = edge;
+  HWND window = reinterpret_cast<HWND>(SHAppBarMessage(ABM_GETAUTOHIDEBAR,
+                                                       &taskbar_data));
+  return (::IsWindow(window) &&
+          (::MonitorFromWindow(window, MONITOR_DEFAULTTONULL) == monitor_) &&
+          (::GetWindowLong(window, GWL_EXSTYLE) & WS_EX_TOPMOST)) ?
+         window : NULL;
+}
+
+gfx::Rect AutoHideBottomBarWin::GetBounds() {
+  ValidateAndGetWindow();
+  if (!window_ || !aligned_to_bottom_)

[jennb, 2011/08/23 20:28:34]

if (!IsEnabled())

[jianli, 2011/08/26 00:18:16]

Changed.

+    return gfx::Rect();
+
+  RECT rect;
+  if (!::GetWindowRect(window_, &rect))
+    return gfx::Rect();
+  return gfx::Rect(rect);
+}
+
+int AutoHideBottomBarWin::GetHeightFromBounds(const gfx::Rect& bounds) const {
+  return bounds.height();
+}
+
+AutoHideBottomBar::Visibility AutoHideBottomBarWin::GetVisibilityFromBounds(
+    const gfx::Rect& bounds) const {
+  if (bounds.bottom() <= work_area_.bottom())
+    return VISIBLE;
+  else if (bounds.y() >= work_area_.bottom() - kAutoHideTaskbarThicknessPx)
+    return HIDDEN;
+  else
+    return ANIMATING;
+}
+
+void AutoHideBottomBarWin::CheckTaskbar() {
+  gfx::Rect bounds = GetBounds();
+
+  // Check and notify the visibility change.
+  Visibility visibility = GetVisibilityFromBounds(bounds);
+  if (visibility != visibility_) {
+    visibility_ = visibility;
+    observer_->OnAutoHideBottomBarVisibilityChanged(visibility);
+  }
+
+  // Check and notify the height change.
+  int height = GetHeightFromBounds(bounds);
+  if (height != height_) {
+    height_ = height;
+    observer_->OnAutoHideBottomBarHeightChanged(height);
+  }
+}
+
+}
+
+// static
+AutoHideBottomBar* AutoHideBottomBar::Create(Observer* observer) {
+  return new AutoHideBottomBarWin(observer);
+}