Keep pan/zoom origin constant for gesture

Author: moffatman

shell/platform/windows/flutter_windows_view.cc

@@ -213,14 +213,11 @@ void FlutterWindowsView::OnPointerPanZoomUpdate(int32_t device_id,
                                                 double pan_y,
                                                 double scale,
                                                 double rotation) {
-  PointerLocation point = binding_handler_->GetPrimaryPointerLocation();
-  SendPointerPanZoomUpdate(device_id, point.x, point.y, pan_x, pan_y, scale,
-                           rotation);
+  SendPointerPanZoomUpdate(device_id, pan_x, pan_y, scale, rotation);
 }
 
 void FlutterWindowsView::OnPointerPanZoomEnd(int32_t device_id) {
-  PointerLocation point = binding_handler_->GetPrimaryPointerLocation();
-  SendPointerPanZoomEnd(device_id, point.x, point.y);
+  SendPointerPanZoomEnd(device_id);
 }
 
 void FlutterWindowsView::OnText(const std::u16string& text) {
@@ -396,6 +393,8 @@ void FlutterWindowsView::SendPointerPanZoomStart(int32_t device_id,
                                                  double y) {
   auto state =
       GetOrCreatePointerState(kFlutterPointerDeviceKindTouch, device_id);
+  state->pan_zoom_start_x = x;
+  state->pan_zoom_start_y = y;
   FlutterPointerEvent event = {};
   event.x = x;
   event.y = y;
@@ -404,17 +403,15 @@ void FlutterWindowsView::SendPointerPanZoomStart(int32_t device_id,
 }
 
 void FlutterWindowsView::SendPointerPanZoomUpdate(int32_t device_id,
-                                                  double x,
-                                                  double y,
                                                   double pan_x,
                                                   double pan_y,
                                                   double scale,
                                                   double rotation) {
   auto state =
       GetOrCreatePointerState(kFlutterPointerDeviceKindTouch, device_id);
   FlutterPointerEvent event = {};
-  event.x = x;
-  event.y = y;
+  event.x = state->pan_zoom_start_x;
+  event.y = state->pan_zoom_start_y;
   event.pan_x = pan_x;
   event.pan_y = pan_y;
   event.scale = scale;
@@ -423,14 +420,12 @@ void FlutterWindowsView::SendPointerPanZoomUpdate(int32_t device_id,
   SendPointerEventWithData(event, state);
 }
 
-void FlutterWindowsView::SendPointerPanZoomEnd(int32_t device_id,
-                                               double x,
-                                               double y) {
+void FlutterWindowsView::SendPointerPanZoomEnd(int32_t device_id) {
   auto state =
       GetOrCreatePointerState(kFlutterPointerDeviceKindTouch, device_id);
   FlutterPointerEvent event = {};
-  event.x = x;
-  event.y = y;
+  event.x = state->pan_zoom_start_x;
+  event.y = state->pan_zoom_start_y;
   event.phase = FlutterPointerPhase::kPanZoomEnd;
   SendPointerEventWithData(event, state);
 }

shell/platform/windows/flutter_windows_view.h

@@ -214,6 +214,12 @@ class FlutterWindowsView : public WindowBindingHandlerDelegate,
 
     // The currently pressed buttons, as represented in FlutterPointerEvent.
     uint64_t buttons = 0;
+
+    // The x position where the last pan/zoom started
+    double pan_zoom_start_x = 0;
+
+    // The y position where the last pan/zoom started
+    double pan_zoom_start_y = 0;
   };
 
   // States a resize event can be in.
@@ -257,14 +263,12 @@ class FlutterWindowsView : public WindowBindingHandlerDelegate,
   void SendPointerPanZoomStart(int32_t device_id, double x, double y);
 
   void SendPointerPanZoomUpdate(int32_t device_id,
-                                double x,
-                                double y,
                                 double pan_x,
                                 double pan_y,
                                 double scale,
                                 double rotation);
 
-  void SendPointerPanZoomEnd(int32_t device_id, double x, double y);
+  void SendPointerPanZoomEnd(int32_t device_id);
 
   // Reports a keyboard character to Flutter engine.
   void SendText(const std::u16string&);