Add scroll wheel support to desktop GLFW shell (#8416)
Sends scroll events from GLFW to the Flutter engine, allowing scrolling
of Scrollables via a scroll wheel.
diff --git a/shell/platform/glfw/flutter_glfw.cc b/shell/platform/glfw/flutter_glfw.cc
index ab03cac..98e76f0 100644
--- a/shell/platform/glfw/flutter_glfw.cc
+++ b/shell/platform/glfw/flutter_glfw.cc
@@ -155,57 +155,86 @@
FlutterEngineSendWindowMetricsEvent(state->engine, &event);
}
-// Sends a pointer event to the Flutter engine with the given phase.
-static void SendPointerEventWithPhase(GLFWwindow* window,
- FlutterPointerPhase phase,
- double x,
- double y) {
- auto state = GetSavedWindowState(window);
+// Sends a pointer event to the Flutter engine based on the given data.
+//
+// Any coordinate/distance values in |event_data| should be in screen
+// coordinates; they will be adjusted to pixel values before being sent.
+static void SendPointerEventWithData(GLFWwindow* window,
+ const FlutterPointerEvent& event_data) {
+ auto* state = GetSavedWindowState(window);
// If sending anything other than an add, and the pointer isn't already added,
// synthesize an add to satisfy Flutter's expectations about events.
- if (!state->pointer_currently_added && phase != FlutterPointerPhase::kAdd) {
- SendPointerEventWithPhase(window, FlutterPointerPhase::kAdd, x, y);
+ if (!state->pointer_currently_added &&
+ event_data.phase != FlutterPointerPhase::kAdd) {
+ FlutterPointerEvent event = {};
+ event.phase = FlutterPointerPhase::kAdd;
+ event.x = event_data.x;
+ event.y = event_data.y;
+ SendPointerEventWithData(window, event);
}
// Don't double-add (e.g., if events are delivered out of order, so an add has
// already been synthesized).
- if (state->pointer_currently_added && phase == FlutterPointerPhase::kAdd) {
+ if (state->pointer_currently_added &&
+ event_data.phase == FlutterPointerPhase::kAdd) {
return;
}
- FlutterPointerEvent event = {};
+ FlutterPointerEvent event = event_data;
+ // Set metadata that's always the same regardless of the event.
event.struct_size = sizeof(event);
- event.phase = phase;
- event.x = x * state->window_pixels_per_screen_coordinate;
- event.y = y * state->window_pixels_per_screen_coordinate;
event.timestamp =
std::chrono::duration_cast<std::chrono::microseconds>(
std::chrono::high_resolution_clock::now().time_since_epoch())
.count();
+ // Convert all screen coordinates to pixel coordinates.
+ event.x *= state->window_pixels_per_screen_coordinate;
+ event.y *= state->window_pixels_per_screen_coordinate;
+ event.scroll_delta_x *= state->window_pixels_per_screen_coordinate;
+ event.scroll_delta_y *= state->window_pixels_per_screen_coordinate;
+
FlutterEngineSendPointerEvent(state->engine, &event, 1);
- if (phase == FlutterPointerPhase::kAdd) {
+ if (event_data.phase == FlutterPointerPhase::kAdd) {
state->pointer_currently_added = true;
- } else if (phase == FlutterPointerPhase::kRemove) {
+ } else if (event_data.phase == FlutterPointerPhase::kRemove) {
state->pointer_currently_added = false;
}
}
+// Updates |event_data| with the current location of the mouse cursor.
+static void SetEventLocationFromCursorPosition(
+ GLFWwindow* window,
+ FlutterPointerEvent* event_data) {
+ glfwGetCursorPos(window, &event_data->x, &event_data->y);
+}
+
+// Set's |event_data|'s phase to either kMove or kHover depending on the current
+// primary mouse button state.
+static void SetEventPhaseFromCursorButtonState(
+ GLFWwindow* window,
+ FlutterPointerEvent* event_data) {
+ event_data->phase =
+ glfwGetMouseButton(window, GLFW_MOUSE_BUTTON_LEFT) == GLFW_PRESS
+ ? FlutterPointerPhase::kMove
+ : FlutterPointerPhase::kHover;
+}
+
// Reports the mouse entering or leaving the Flutter view.
static void GLFWCursorEnterCallback(GLFWwindow* window, int entered) {
- double x, y;
- glfwGetCursorPos(window, &x, &y);
- FlutterPointerPhase phase =
+ FlutterPointerEvent event = {};
+ event.phase =
entered ? FlutterPointerPhase::kAdd : FlutterPointerPhase::kRemove;
- SendPointerEventWithPhase(window, phase, x, y);
+ SetEventLocationFromCursorPosition(window, &event);
+ SendPointerEventWithData(window, event);
}
// Reports mouse movement to the Flutter engine.
static void GLFWCursorPositionCallback(GLFWwindow* window, double x, double y) {
- bool button_down =
- glfwGetMouseButton(window, GLFW_MOUSE_BUTTON_LEFT) == GLFW_PRESS;
- FlutterPointerPhase phase =
- button_down ? FlutterPointerPhase::kMove : FlutterPointerPhase::kHover;
- SendPointerEventWithPhase(window, phase, x, y);
+ FlutterPointerEvent event = {};
+ event.x = x;
+ event.y = y;
+ SetEventPhaseFromCursorButtonState(window, &event);
+ SendPointerEventWithData(window, event);
}
// Reports mouse button press to the Flutter engine.
@@ -219,12 +248,11 @@
return;
}
- double x, y;
- glfwGetCursorPos(window, &x, &y);
- FlutterPointerPhase phase = (action == GLFW_PRESS)
- ? FlutterPointerPhase::kDown
- : FlutterPointerPhase::kUp;
- SendPointerEventWithPhase(window, phase, x, y);
+ FlutterPointerEvent event = {};
+ event.phase = (action == GLFW_PRESS) ? FlutterPointerPhase::kDown
+ : FlutterPointerPhase::kUp;
+ SetEventLocationFromCursorPosition(window, &event);
+ SendPointerEventWithData(window, event);
// If mouse tracking isn't already enabled, turn it on for the duration of
// the drag to generate kMove events.
@@ -242,6 +270,22 @@
}
}
+// Reports scroll wheel events to the Flutter engine.
+static void GLFWScrollCallback(GLFWwindow* window,
+ double delta_x,
+ double delta_y) {
+ FlutterPointerEvent event = {};
+ SetEventLocationFromCursorPosition(window, &event);
+ SetEventPhaseFromCursorButtonState(window, &event);
+ event.signal_kind = FlutterPointerSignalKind::kFlutterPointerSignalKindScroll;
+ // TODO: See if this can be queried from the OS; this value is chosen
+ // arbitrarily to get something that feels reasonable.
+ const int kScrollOffsetMultiplier = 20;
+ event.scroll_delta_x = delta_x * kScrollOffsetMultiplier;
+ event.scroll_delta_y = -delta_y * kScrollOffsetMultiplier;
+ SendPointerEventWithData(window, event);
+}
+
// Passes character input events to registered handlers.
static void GLFWCharCallback(GLFWwindow* window, unsigned int code_point) {
for (const auto& handler :
@@ -276,6 +320,7 @@
glfwSetKeyCallback(window, GLFWKeyCallback);
glfwSetCharCallback(window, GLFWCharCallback);
glfwSetMouseButtonCallback(window, GLFWMouseButtonCallback);
+ glfwSetScrollCallback(window, GLFWScrollCallback);
if (GetSavedWindowState(window)->hover_tracking_enabled) {
SetHoverCallbacksEnabled(window, true);
}
@@ -286,6 +331,7 @@
glfwSetKeyCallback(window, nullptr);
glfwSetCharCallback(window, nullptr);
glfwSetMouseButtonCallback(window, nullptr);
+ glfwSetScrollCallback(window, nullptr);
SetHoverCallbacksEnabled(window, false);
}
