Fix painting of scaled themes in Windows in high-DPI mode.

ui/native_theme/native_theme_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 "ui/native_theme/native_theme_win.h"
 
 #include <windows.h>
 #include <uxtheme.h>
 #include <vsstyle.h>
 #include <vssym32.h>
 
 #include "base/basictypes.h"
 #include "base/logging.h"
 #include "base/memory/scoped_handle.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/win/scoped_gdi_object.h"
 #include "base/win/scoped_hdc.h"
 #include "base/win/scoped_select_object.h"
 #include "base/win/windows_version.h"
 #include "skia/ext/bitmap_platform_device.h"
 #include "skia/ext/platform_canvas.h"
 #include "skia/ext/skia_utils_win.h"
 #include "third_party/skia/include/core/SkCanvas.h"
 #include "third_party/skia/include/core/SkColorPriv.h"
 #include "third_party/skia/include/core/SkShader.h"
+#include "ui/base/win/dpi.h"
 #include "ui/gfx/color_utils.h"
 #include "ui/gfx/gdi_util.h"
 #include "ui/gfx/rect.h"
+#include "ui/gfx/rect_conversions.h"
 #include "ui/native_theme/common_theme.h"
 
 // This was removed from Winvers.h but is still used.
 #if !defined(COLOR_MENUHIGHLIGHT)
 #define COLOR_MENUHIGHLIGHT 29
 #endif
 
 namespace {
 
 // TODO: Obtain the correct colors using GetSysColor.
@@ skipping 1025 matching lines @@
           state_id = ABS_RIGHTHOVER;
           break;
         case kScrollbarUpArrow:
           state_id = ABS_UPHOVER;
           break;
         default:
           NOTREACHED() << "Invalid part: " << part;
           break;
       }
     }
-
-    return draw_theme_(handle, hdc, SBP_ARROWBTN, state_id, &rect_win, NULL);
+    return PaintScaledTheme(handle, hdc, SBP_ARROWBTN, state_id, rect);
   }
 
   int classic_state = DFCS_SCROLLDOWN;
   switch (part) {
     case kScrollbarDownArrow:
       classic_state = DFCS_SCROLLDOWN;
       break;
     case kScrollbarLeftArrow:
       classic_state = DFCS_SCROLLLEFT;
       break;
@@ skipping 68 matching lines @@
       break;
     case kPressed:
       state_id = SCRBS_PRESSED;
       break;
     default:
       NOTREACHED() << "Invalid state: " << state;
       break;
   }
 
   if (handle && draw_theme_)
-    return draw_theme_(handle, hdc, part_id, state_id, &rect_win, NULL);
+    return PaintScaledTheme(handle, hdc, part_id, state_id, rect);
 
   // Draw it manually.
   if ((part_id == SBP_THUMBBTNHORZ) || (part_id == SBP_THUMBBTNVERT))
     DrawEdge(hdc, &rect_win, EDGE_RAISED, BF_RECT | BF_MIDDLE);
   // Classic mode doesn't have a gripper.
   return S_OK;
 }
 
 HRESULT NativeThemeWin::PaintScrollbarTrack(
     SkCanvas* canvas,
@@ skipping 409 matching lines @@
     if (fill_content_area) {
       FillRect(hdc, rect, (classic_state & DFCS_INACTIVE) ?
                    reinterpret_cast<HBRUSH>(COLOR_BTNFACE + 1) : bg_brush);
     }
     hr = S_OK;
   }
   DeleteObject(bg_brush);
   return hr;
 }
 
+HRESULT NativeThemeWin::PaintScaledTheme(HANDLE theme,
+                                         HDC hdc,
+                                         int part_id,
+                                         int state_id,
+                                         const gfx::Rect& rect) const {
+  // Correct the scaling and positioning of sub-components such as scrollbar
+  // arrows and thumb grippers in the event that the world transform applies
+  // scaling (e.g. in high-DPI mode).
+  XFORM save_transform;
+  if (GetWorldTransform(hdc, &save_transform)) {
+    float scale = save_transform.eM11;
+    if (scale != 1 && save_transform.eM12 == 0) {
+      ModifyWorldTransform(hdc, NULL, MWT_IDENTITY);
+      gfx::Rect scaled_rect = gfx::ToEnclosedRect(
+          gfx::ScaleRect(rect, scale));
+      RECT bounds = gfx::Rect(scaled_rect.x() + save_transform.eDx,
+                              scaled_rect.y() + save_transform.eDy,
+                              scaled_rect.width(),
+                              scaled_rect.height()).ToRECT();
+      HRESULT result = draw_theme_(theme, hdc, part_id, state_id, &bounds,
+                                   NULL);
+      SetWorldTransform(hdc, &save_transform);
+      return result;
+    }
+  }
+  RECT bounds = rect.ToRECT();
+  return draw_theme_(theme, hdc, part_id, state_id, &bounds, NULL);
+}
+
 // static
 NativeThemeWin::ThemeName NativeThemeWin::GetThemeName(Part part) {
   ThemeName name;
   switch (part) {
     case kCheckbox:
     case kRadio:
     case kPushButton:
       name = BUTTON;
       break;
     case kInnerSpinButton:
@@ skipping 423 matching lines @@
     handle = open_theme_(NULL, L"Spin");
     break;
   default:
     NOTREACHED();
   }
   theme_handles_[theme_name] = handle;
   return handle;
 }
 
 }  // namespace ui