Flutter Windows Embedder
cursor_handler.cc
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1 // Copyright 2013 The Flutter Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4 
6 
7 #include <windows.h>
8 
12 
13 static constexpr char kChannelName[] = "flutter/mousecursor";
14 
15 static constexpr char kActivateSystemCursorMethod[] = "activateSystemCursor";
16 static constexpr char kKindKey[] = "kind";
17 
18 // This method allows creating a custom cursor with rawBGRA buffer, returns a
19 // string to identify the cursor.
20 static constexpr char kCreateCustomCursorMethod[] =
21  "createCustomCursor/windows";
22 // A string, the custom cursor's name.
23 static constexpr char kCustomCursorNameKey[] = "name";
24 // A list of bytes, the custom cursor's rawBGRA buffer.
25 static constexpr char kCustomCursorBufferKey[] = "buffer";
26 // A double, the x coordinate of the custom cursor's hotspot, starting from
27 // left.
28 static constexpr char kCustomCursorHotXKey[] = "hotX";
29 // A double, the y coordinate of the custom cursor's hotspot, starting from top.
30 static constexpr char kCustomCursorHotYKey[] = "hotY";
31 // An int value for the width of the custom cursor.
32 static constexpr char kCustomCursorWidthKey[] = "width";
33 // An int value for the height of the custom cursor.
34 static constexpr char kCustomCursorHeightKey[] = "height";
35 
36 // This method also has an argument `kCustomCursorNameKey` for the name
37 // of the cursor to activate.
38 static constexpr char kSetCustomCursorMethod[] = "setCustomCursor/windows";
39 
40 // This method also has an argument `kCustomCursorNameKey` for the name
41 // of the cursor to delete.
42 static constexpr char kDeleteCustomCursorMethod[] =
43  "deleteCustomCursor/windows";
44 
45 // Error codes used for responses.
46 static constexpr char kCursorError[] = "Cursor error";
47 
48 namespace flutter {
49 
51  FlutterWindowsEngine* engine)
52  : channel_(std::make_unique<MethodChannel<EncodableValue>>(
53  messenger,
55  &StandardMethodCodec::GetInstance())),
56  engine_(engine) {
57  channel_->SetMethodCallHandler(
58  [this](const MethodCall<EncodableValue>& call,
59  std::unique_ptr<MethodResult<EncodableValue>> result) {
60  HandleMethodCall(call, std::move(result));
61  });
62 }
63 
64 void CursorHandler::HandleMethodCall(
65  const MethodCall<EncodableValue>& method_call,
66  std::unique_ptr<MethodResult<EncodableValue>> result) {
67  const std::string& method = method_call.method_name();
68  if (method.compare(kActivateSystemCursorMethod) == 0) {
69  const auto& arguments = std::get<EncodableMap>(*method_call.arguments());
70  auto kind_iter = arguments.find(EncodableValue(std::string(kKindKey)));
71  if (kind_iter == arguments.end()) {
72  result->Error("Argument error",
73  "Missing argument while trying to activate system cursor");
74  return;
75  }
76  const auto& kind = std::get<std::string>(kind_iter->second);
77 
78  // TODO(loicsharma): Remove implicit view assumption.
79  // https://github.com/flutter/flutter/issues/142845
80  FlutterWindowsView* view = engine_->view(kImplicitViewId);
81  if (view == nullptr) {
82  result->Error(kCursorError,
83  "Cursor is not available in Windows headless mode");
84  return;
85  }
86  view->UpdateFlutterCursor(kind);
87  result->Success();
88  } else if (method.compare(kCreateCustomCursorMethod) == 0) {
89  const auto& arguments = std::get<EncodableMap>(*method_call.arguments());
90  auto name_iter =
91  arguments.find(EncodableValue(std::string(kCustomCursorNameKey)));
92  if (name_iter == arguments.end()) {
93  result->Error(
94  "Argument error",
95  "Missing argument name while trying to customize system cursor");
96  return;
97  }
98  auto name = std::get<std::string>(name_iter->second);
99  auto buffer_iter =
100  arguments.find(EncodableValue(std::string(kCustomCursorBufferKey)));
101  if (buffer_iter == arguments.end()) {
102  result->Error(
103  "Argument error",
104  "Missing argument buffer while trying to customize system cursor");
105  return;
106  }
107  auto buffer = std::get<std::vector<uint8_t>>(buffer_iter->second);
108  auto width_iter =
109  arguments.find(EncodableValue(std::string(kCustomCursorWidthKey)));
110  if (width_iter == arguments.end()) {
111  result->Error(
112  "Argument error",
113  "Missing argument width while trying to customize system cursor");
114  return;
115  }
116  auto width = std::get<int>(width_iter->second);
117  auto height_iter =
118  arguments.find(EncodableValue(std::string(kCustomCursorHeightKey)));
119  if (height_iter == arguments.end()) {
120  result->Error(
121  "Argument error",
122  "Missing argument height while trying to customize system cursor");
123  return;
124  }
125  auto height = std::get<int>(height_iter->second);
126  auto hot_x_iter =
127  arguments.find(EncodableValue(std::string(kCustomCursorHotXKey)));
128  if (hot_x_iter == arguments.end()) {
129  result->Error(
130  "Argument error",
131  "Missing argument hotX while trying to customize system cursor");
132  return;
133  }
134  auto hot_x = std::get<double>(hot_x_iter->second);
135  auto hot_y_iter =
136  arguments.find(EncodableValue(std::string(kCustomCursorHotYKey)));
137  if (hot_y_iter == arguments.end()) {
138  result->Error(
139  "Argument error",
140  "Missing argument hotY while trying to customize system cursor");
141  return;
142  }
143  auto hot_y = std::get<double>(hot_y_iter->second);
144  HCURSOR cursor = GetCursorFromBuffer(buffer, hot_x, hot_y, width, height);
145  if (cursor == nullptr) {
146  result->Error("Argument error",
147  "Argument must contains a valid rawBGRA bitmap");
148  return;
149  }
150  // Push the cursor into the cache map.
151  custom_cursors_.emplace(name, std::move(cursor));
152  result->Success(flutter::EncodableValue(std::move(name)));
153  } else if (method.compare(kSetCustomCursorMethod) == 0) {
154  const auto& arguments = std::get<EncodableMap>(*method_call.arguments());
155  auto name_iter =
156  arguments.find(EncodableValue(std::string(kCustomCursorNameKey)));
157  if (name_iter == arguments.end()) {
158  result->Error("Argument error",
159  "Missing argument key while trying to set a custom cursor");
160  return;
161  }
162  auto name = std::get<std::string>(name_iter->second);
163  if (custom_cursors_.find(name) == custom_cursors_.end()) {
164  result->Error(
165  "Argument error",
166  "The custom cursor identified by the argument key cannot be found");
167  return;
168  }
169  HCURSOR cursor = custom_cursors_[name];
170 
171  // TODO(loicsharma): Remove implicit view assumption.
172  // https://github.com/flutter/flutter/issues/142845
173  FlutterWindowsView* view = engine_->view(kImplicitViewId);
174  if (view == nullptr) {
175  result->Error(kCursorError,
176  "Cursor is not available in Windows headless mode");
177  return;
178  }
179  view->SetFlutterCursor(cursor);
180  result->Success();
181  } else if (method.compare(kDeleteCustomCursorMethod) == 0) {
182  const auto& arguments = std::get<EncodableMap>(*method_call.arguments());
183  auto name_iter =
184  arguments.find(EncodableValue(std::string(kCustomCursorNameKey)));
185  if (name_iter == arguments.end()) {
186  result->Error(
187  "Argument error",
188  "Missing argument key while trying to delete a custom cursor");
189  return;
190  }
191  auto name = std::get<std::string>(name_iter->second);
192  auto it = custom_cursors_.find(name);
193  // If the specified cursor name is not found, the deletion is a noop and
194  // returns success.
195  if (it != custom_cursors_.end()) {
196  DeleteObject(it->second);
197  custom_cursors_.erase(it);
198  }
199  result->Success();
200  } else {
201  result->NotImplemented();
202  }
203 }
204 
205 HCURSOR GetCursorFromBuffer(const std::vector<uint8_t>& buffer,
206  double hot_x,
207  double hot_y,
208  int width,
209  int height) {
210  HCURSOR cursor = nullptr;
211  HDC display_dc = GetDC(NULL);
212  // Flutter should returns rawBGRA, which has 8bits * 4channels.
213  BITMAPINFO bmi;
214  memset(&bmi, 0, sizeof(bmi));
215  bmi.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
216  bmi.bmiHeader.biWidth = width;
217  bmi.bmiHeader.biHeight = -height;
218  bmi.bmiHeader.biPlanes = 1;
219  bmi.bmiHeader.biBitCount = 32;
220  bmi.bmiHeader.biCompression = BI_RGB;
221  bmi.bmiHeader.biSizeImage = width * height * 4;
222  // Create the pixmap DIB section
223  uint8_t* pixels = 0;
224  HBITMAP bitmap =
225  CreateDIBSection(display_dc, &bmi, DIB_RGB_COLORS, (void**)&pixels, 0, 0);
226  ReleaseDC(0, display_dc);
227  if (!bitmap || !pixels) {
228  return nullptr;
229  }
230  int bytes_per_line = width * 4;
231  for (int y = 0; y < height; ++y) {
232  memcpy(pixels + y * bytes_per_line, &buffer[bytes_per_line * y],
233  bytes_per_line);
234  }
235  HBITMAP mask;
236  GetMaskBitmaps(bitmap, mask);
237  ICONINFO icon_info;
238  icon_info.fIcon = 0;
239  icon_info.xHotspot = hot_x;
240  icon_info.yHotspot = hot_y;
241  icon_info.hbmMask = mask;
242  icon_info.hbmColor = bitmap;
243  cursor = CreateIconIndirect(&icon_info);
244  DeleteObject(mask);
245  DeleteObject(bitmap);
246  return cursor;
247 }
248 
249 void GetMaskBitmaps(HBITMAP bitmap, HBITMAP& mask_bitmap) {
250  HDC h_dc = ::GetDC(NULL);
251  HDC h_main_dc = ::CreateCompatibleDC(h_dc);
252  HDC h_and_mask_dc = ::CreateCompatibleDC(h_dc);
253 
254  // Get the dimensions of the source bitmap
255  BITMAP bm;
256  ::GetObject(bitmap, sizeof(BITMAP), &bm);
257  mask_bitmap = ::CreateCompatibleBitmap(h_dc, bm.bmWidth, bm.bmHeight);
258 
259  // Select the bitmaps to DC
260  HBITMAP h_old_main_bitmap = (HBITMAP)::SelectObject(h_main_dc, bitmap);
261  HBITMAP h_old_and_mask_bitmap =
262  (HBITMAP)::SelectObject(h_and_mask_dc, mask_bitmap);
263 
264  // Scan each pixel of the souce bitmap and create the masks
265  COLORREF main_bit_pixel;
266  for (int x = 0; x < bm.bmWidth; ++x) {
267  for (int y = 0; y < bm.bmHeight; ++y) {
268  main_bit_pixel = ::GetPixel(h_main_dc, x, y);
269  if (main_bit_pixel == RGB(0, 0, 0)) {
270  ::SetPixel(h_and_mask_dc, x, y, RGB(255, 255, 255));
271  } else {
272  ::SetPixel(h_and_mask_dc, x, y, RGB(0, 0, 0));
273  }
274  }
275  }
276  ::SelectObject(h_main_dc, h_old_main_bitmap);
277  ::SelectObject(h_and_mask_dc, h_old_and_mask_bitmap);
278 
279  ::DeleteDC(h_and_mask_dc);
280  ::DeleteDC(h_main_dc);
281 
282  ::ReleaseDC(NULL, h_dc);
283 }
284 
285 } // namespace flutter
flutter::kImplicitViewId
constexpr FlutterViewId kImplicitViewId
Definition: flutter_windows_engine.h:54
flutter::FlutterWindowsEngine::view
FlutterWindowsView * view(FlutterViewId view_id) const
Definition: flutter_windows_engine.cc:533
kCustomCursorHeightKey
static constexpr char kCustomCursorHeightKey[]
Definition: cursor_handler.cc:34
kCursorError
static constexpr char kCursorError[]
Definition: cursor_handler.cc:46
flutter::MethodChannel
Definition: method_channel.h:34
flutter::GetCursorFromBuffer
HCURSOR GetCursorFromBuffer(const std::vector< uint8_t > &buffer, double hot_x, double hot_y, int width, int height)
Definition: cursor_handler.cc:205
flutter::FlutterWindowsEngine
Definition: flutter_windows_engine.h:89
kDeleteCustomCursorMethod
static constexpr char kDeleteCustomCursorMethod[]
Definition: cursor_handler.cc:42
kCustomCursorHotXKey
static constexpr char kCustomCursorHotXKey[]
Definition: cursor_handler.cc:28
flutter::StandardMethodCodec
Definition: standard_method_codec.h:18
standard_method_codec.h
kSetCustomCursorMethod
static constexpr char kSetCustomCursorMethod[]
Definition: cursor_handler.cc:38
kCustomCursorNameKey
static constexpr char kCustomCursorNameKey[]
Definition: cursor_handler.cc:23
kActivateSystemCursorMethod
static constexpr char kActivateSystemCursorMethod[]
Definition: cursor_handler.cc:15
flutter::BinaryMessenger
Definition: binary_messenger.h:28
flutter_windows_view.h
kKindKey
static constexpr char kKindKey[]
Definition: cursor_handler.cc:16
flutter::MethodCall
Definition: method_call.h:18
flutter::GetMaskBitmaps
void GetMaskBitmaps(HBITMAP bitmap, HBITMAP &mask_bitmap)
Definition: cursor_handler.cc:249
flutter
Definition: accessibility_bridge_windows.cc:11
flutter::FlutterWindowsView::UpdateFlutterCursor
void UpdateFlutterCursor(const std::string &cursor_name)
Definition: flutter_windows_view.cc:163
flutter::FlutterWindowsView::SetFlutterCursor
void SetFlutterCursor(HCURSOR cursor)
Definition: flutter_windows_view.cc:167
kCustomCursorWidthKey
static constexpr char kCustomCursorWidthKey[]
Definition: cursor_handler.cc:32
kCreateCustomCursorMethod
static constexpr char kCreateCustomCursorMethod[]
Definition: cursor_handler.cc:20
kChannelName
static constexpr char kChannelName[]
Definition: cursor_handler.cc:13
flutter::EncodableValue
Definition: encodable_value.h:165
flutter_windows_engine.h
flutter::MethodCall::method_name
const std::string & method_name() const
Definition: method_call.h:31
flutter::MethodResult< EncodableValue >
kCustomCursorBufferKey
static constexpr char kCustomCursorBufferKey[]
Definition: cursor_handler.cc:25
flutter::CursorHandler::CursorHandler
CursorHandler(flutter::BinaryMessenger *messenger, flutter::FlutterWindowsEngine *engine)
Definition: cursor_handler.cc:50
cursor_handler.h
flutter::MethodCall::arguments
const T * arguments() const
Definition: method_call.h:34
kCustomCursorHotYKey
static constexpr char kCustomCursorHotYKey[]
Definition: cursor_handler.cc:30