Fix bug 105043: Panels [WIN]: For minimize panels, taskbar hover preview show the 4-pixel represent…

chrome/browser/ui/panels/taskbar_window_thumbnailer_win.cc

Index: chrome/browser/ui/panels/taskbar_window_thumbnailer_win.cc
diff --git a/chrome/browser/ui/panels/taskbar_window_thumbnailer_win.cc b/chrome/browser/ui/panels/taskbar_window_thumbnailer_win.cc
new file mode 100644
index 0000000000000000000000000000000000000000..9f20f982e96d2c81149ffb156a3e6aa38a70315b
--- /dev/null
+++ b/chrome/browser/ui/panels/taskbar_window_thumbnailer_win.cc
@@ -0,0 +1,129 @@
+// 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/panels/taskbar_window_thumbnailer_win.h"
+
+#include "base/logging.h"
+#include "skia/ext/image_operations.h"
+#include "ui/gfx/canvas.h"
+#include "ui/gfx/gdi_util.h"
+
+namespace {
+
+HBITMAP GetNativeBitmapFromSkBitmap(const SkBitmap& bitmap) {
+  int width = bitmap.width();
+  int height = bitmap.height();
+
+  BITMAPV4HEADER native_bitmap_header;
+  gfx::CreateBitmapV4Header(width, height, &native_bitmap_header);
+
+  HDC dc = ::GetDC(NULL);
+  void* bits;
+  HBITMAP native_bitmap = ::CreateDIBSection(dc,
+      reinterpret_cast<BITMAPINFO*>(&native_bitmap_header),
+      DIB_RGB_COLORS,
+      &bits,
+      NULL,
+      0);
+  DCHECK(native_bitmap);
+  ::ReleaseDC(NULL, dc);
+  bitmap.copyPixelsTo(bits, width * height * 4, width * 4);
+  return native_bitmap;
+}
+
+void EnableCustomThumbnail(HWND hwnd, bool enable) {
+  BOOL enable_value = enable;
+  ::DwmSetWindowAttribute(hwnd,
+                          DWMWA_FORCE_ICONIC_REPRESENTATION,
+                          &enable,
+                          sizeof(enable_value));
+  ::DwmSetWindowAttribute(hwnd,
+                          DWMWA_HAS_ICONIC_BITMAP,
+                          &enable,
+                          sizeof(enable_value));
+}
+
+}  // namespace
+
+
+TaskbarWindowThumbnailerWin::TaskbarWindowThumbnailerWin(HWND hwnd)
+    : hwnd_(hwnd) {
+  capture_bitmap_.reset(CaptureWindowImage());
+  EnableCustomThumbnail(hwnd_, true);
+}
+
+TaskbarWindowThumbnailerWin::~TaskbarWindowThumbnailerWin() {
+  EnableCustomThumbnail(hwnd_, false);
+}
+
+bool TaskbarWindowThumbnailerWin::FilterMessage(HWND hwnd,
+                                                UINT message,
+                                                WPARAM w_param,
+                                                LPARAM l_param,
+                                                LRESULT* l_result) {
+  DCHECK_EQ(hwnd_, hwnd);
+  switch (message) {
+    case WM_DWMSENDICONICTHUMBNAIL:
+      return OnDwmSendIconicThumbnail(HIWORD(l_param),
+                                      LOWORD(l_param),
+                                      l_result);
+    case WM_DWMSENDICONICLIVEPREVIEWBITMAP:
+      return OnDwmSendIconicLivePreviewBitmap(l_result);
+  }
+  return false;
+}
+
+bool TaskbarWindowThumbnailerWin::OnDwmSendIconicThumbnail(
+    int width, int height, LRESULT* l_result) {
+  DCHECK(capture_bitmap_.get());
+
+  SkBitmap* thumbnail_bitmap = capture_bitmap_.get();
+
+  // Scale the image if needed.
+  SkBitmap scaled_bitmap;
+  if (capture_bitmap_->width() != width ||
+      capture_bitmap_->height() != height) {
+    double x_scale = static_cast<double>(width) / capture_bitmap_->width();
+    double y_scale = static_cast<double>(height) / capture_bitmap_->height();
+    double scale = std::min(x_scale, y_scale);
+    width = capture_bitmap_->width() * scale;
+    height = capture_bitmap_->height() * scale;
+    scaled_bitmap = skia::ImageOperations::Resize(
+        *capture_bitmap_, skia::ImageOperations::RESIZE_GOOD, width, height);
+    thumbnail_bitmap = &scaled_bitmap;
+  }
+
+  HBITMAP native_bitmap = GetNativeBitmapFromSkBitmap(*thumbnail_bitmap);
+  ::DwmSetIconicThumbnail(hwnd_, native_bitmap, 0);
+  ::DeleteObject(native_bitmap);
+
+  *l_result = 0;
+  return true;
+}
+
+bool TaskbarWindowThumbnailerWin::OnDwmSendIconicLivePreviewBitmap(
+    LRESULT* l_result) {
+  scoped_ptr<SkBitmap> live_bitmap(CaptureWindowImage());
+  HBITMAP native_bitmap = GetNativeBitmapFromSkBitmap(*live_bitmap);
+  ::DwmSetIconicLivePreviewBitmap(hwnd_, native_bitmap, NULL, 0);
+  ::DeleteObject(native_bitmap);
+
+  *l_result = 0;
+  return true;
+}
+
+SkBitmap* TaskbarWindowThumbnailerWin::CaptureWindowImage() const {
+  RECT bounds;
+  ::GetWindowRect(hwnd_, &bounds);
+  int width = bounds.right - bounds.left;
+  int height = bounds.bottom - bounds.top;
+
+  gfx::Canvas canvas(gfx::Size(width, height), false);
+  HDC target_dc = canvas.BeginPlatformPaint();
+  HDC source_dc = ::GetDC(hwnd_);
+  ::BitBlt(target_dc, 0, 0, width, height, source_dc, 0, 0, SRCCOPY);
+  ::ReleaseDC(hwnd_, source_dc);
+  canvas.EndPlatformPaint();
+  return new SkBitmap(canvas.ExtractBitmap());
+}