Fix for 504133 - wandering identity switcher button

chrome/browser/ui/views/frame/minimize_button_metrics_win.cc

 // Copyright (c) 2012 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/views/frame/minimize_button_metrics_win.h"
 
 #include "base/logging.h"
 #include "base/i18n/rtl.h"
+#include "dwmapi.h"
 #include "ui/base/win/shell.h"
 #include "ui/display/win/dpi.h"
+#include "ui/display/win/screen_win.h"
 
 namespace {
 
-int GetMinimizeButtonOffsetForWindow(HWND hwnd) {
-  // The WM_GETTITLEBARINFOEX message can fail if we are not active/visible. By
-  // fail we get a location of 0; the return status code is always the same and
-  // similarly the state never seems to change (titlebar_info.rgstate).
-  TITLEBARINFOEX titlebar_info = {0};
-  titlebar_info.cbSize = sizeof(TITLEBARINFOEX);
-  SendMessage(hwnd, WM_GETTITLEBARINFOEX, 0,
-              reinterpret_cast<WPARAM>(&titlebar_info));
+using display::win::ScreenWin;
 
-  if (titlebar_info.rgrect[2].left == titlebar_info.rgrect[2].right ||
+int GetMinimizeButtonOffsetForWindow(HWND hwnd, bool was_activated) {
+  bool dwm_button_pos = false;
+  POINT minimize_button_corner = { 0 };
+  RECT button_bounds = { 0 };
+  if (SUCCEEDED(DwmGetWindowAttribute(hwnd, DWMWA_CAPTION_BUTTON_BOUNDS,
+       &button_bounds, sizeof(button_bounds)))) {
+    if (button_bounds.left != button_bounds.right) {
+      // This converts the button coordinate into screen coordinates
+      // thus, ensuring that the identity switcher is placed in the
+      // same location as before.
+      RECT window_bounds = { 0 };
+      if (GetWindowRect(hwnd, &window_bounds)) {
+        minimize_button_corner =
+          { button_bounds.left + window_bounds.left, 0 };

[sky, 2016/05/04 17:42:03]

nit: run git cl format (this should at least be 4 space indented).

[kylix_rd, 2016/05/04 17:59:04]

Done.

+        dwm_button_pos = true;
+      }
+    }
+  }
+  if (!dwm_button_pos) {
+    // Fallback to using the message for the titlebar info only if the above
+    // code fails. It can fail if DWM is disabled globally or only for the
+    // given HWND. The WM_GETTITLEBARINFOEX message can fail if we are not
+    // active/visible. By fail we get a location of 0; the return status
+    // code is always the same and similarly the state never seems to change
+    // (titlebar_info.rgstate).
+    TITLEBARINFOEX titlebar_info = { 0 };
+    titlebar_info.cbSize = sizeof(TITLEBARINFOEX);
+    SendMessage(hwnd, WM_GETTITLEBARINFOEX, 0,
+      reinterpret_cast<WPARAM>(&titlebar_info));
+
+    // Under DWM WM_GETTITLEBARINFOEX won't return the right thing until after
+    // WM_NCACTIVATE (maybe it returns classic values?). In an attempt to
+    // return a consistant value we cache the last value across instances and
+    // use it until we get the activate.
+    if (!was_activated ||
+       titlebar_info.rgrect[2].left == titlebar_info.rgrect[2].right ||

[sky, 2016/05/04 17:42:03]

formatting here is equally wrong (again, git cl format will fix it).

[kylix_rd, 2016/05/04 17:59:04]

Done.

       (titlebar_info.rgstate[2] & (STATE_SYSTEM_INVISIBLE |
-                                   STATE_SYSTEM_OFFSCREEN |
-                                   STATE_SYSTEM_UNAVAILABLE))) {
-    return 0;
+        STATE_SYSTEM_OFFSCREEN |

[sky, 2016/05/04 17:42:03]

here too.

[kylix_rd, 2016/05/04 17:59:04]

Done.

+        STATE_SYSTEM_UNAVAILABLE))) {
+      return 0;
+    }
+    minimize_button_corner = { titlebar_info.rgrect[2].left, 0 };
   }
 
   // WM_GETTITLEBARINFOEX returns rects in screen coordinates in pixels.
-  // We need to convert the minimize button corner offset to DIP before
-  // returning it.
-  POINT minimize_button_corner = { titlebar_info.rgrect[2].left, 0 };
+  // DWMNA_CAPTION_BUTTON_BOUNDS is in window (not client) coordinates,
+  // but it has been converted to screen coordinates above. We need to
+  // convert the minimize button corner offset to DIP before returning it.
   MapWindowPoints(HWND_DESKTOP, hwnd, &minimize_button_corner, 1);
-  return minimize_button_corner.x / display::win::GetDPIScale();
+  gfx::Point pixel_point = { minimize_button_corner.x, 0 };
+  gfx::Point dip_point = ScreenWin::ClientToDIPPoint(hwnd, pixel_point);
+  return dip_point.x();
 }
 
 }  // namespace
 
 // static
 int MinimizeButtonMetrics::last_cached_minimize_button_x_delta_ = 0;
 
 MinimizeButtonMetrics::MinimizeButtonMetrics()
     : hwnd_(nullptr),
       cached_minimize_button_x_delta_(last_cached_minimize_button_x_delta_),
       was_activated_(false) {
 }
 
 MinimizeButtonMetrics::~MinimizeButtonMetrics() {
 }
 
 void MinimizeButtonMetrics::Init(HWND hwnd) {
   DCHECK(!hwnd_);
   hwnd_ = hwnd;
 }
 
 void MinimizeButtonMetrics::OnHWNDActivated() {
   was_activated_ = true;
-  // NOTE: we don't cache here as it seems only after the activate is the value
-  // correct.
+  // NOTE: we don't cache here as it seems only after the activate is the
+  // value correct.
 }
 
 int MinimizeButtonMetrics::GetMinimizeButtonOffsetX() const {
-  // Under DWM WM_GETTITLEBARINFOEX won't return the right thing until after
-  // WM_NCACTIVATE (maybe it returns classic values?). In an attempt to return a
-  // consistant value we cache the last value across instances and use it until
-  // we get the activate.
-  if (was_activated_ || !ui::win::IsAeroGlassEnabled() ||
-      cached_minimize_button_x_delta_ == 0) {
+  if (!ui::win::IsAeroGlassEnabled() || cached_minimize_button_x_delta_ == 0) {
     const int minimize_button_offset = GetAndCacheMinimizeButtonOffsetX();
     if (minimize_button_offset > 0)
       return minimize_button_offset;
   }
 
   // If we fail to get the minimize button offset via the WM_GETTITLEBARINFOEX
-  // message then calculate and return this via the
+  // message or DwmGetWindowAttribute then calculate and return this via the
   // cached_minimize_button_x_delta_ member value. Please see
   // CacheMinimizeButtonDelta() for more details.
   DCHECK(cached_minimize_button_x_delta_);
 
   if (base::i18n::IsRTL())
     return cached_minimize_button_x_delta_;
 
   RECT client_rect = {0};
   GetClientRect(hwnd_, &client_rect);
   return client_rect.right - cached_minimize_button_x_delta_;
 }
 
 int MinimizeButtonMetrics::GetAndCacheMinimizeButtonOffsetX() const {
-  const int minimize_button_offset = GetMinimizeButtonOffsetForWindow(hwnd_);
+  const int minimize_button_offset =
+    GetMinimizeButtonOffsetForWindow(hwnd_, was_activated_);
   if (minimize_button_offset <= 0)
     return 0;
 
   if (base::i18n::IsRTL()) {
     cached_minimize_button_x_delta_ = minimize_button_offset;
   } else {
     RECT client_rect = {0};
     GetClientRect(hwnd_, &client_rect);
     cached_minimize_button_x_delta_ =
         client_rect.right - minimize_button_offset;
   }
   last_cached_minimize_button_x_delta_ = cached_minimize_button_x_delta_;
   return minimize_button_offset;
 }