feat(wayland): touch, with the first finger standing in for the pointer

The seat's wl_touch was never bound, so a touchscreen could not drive a
window at all. Every finger is now reported through onTouchDown, onTouchMove,
onTouchUp and onTouchCancel (TouchPoint: the compositor's id and the
position in physical pixels). The first finger down also enters the window —
Device::focusedWindow and the pointer serial the clipboard needs — presses
the left button, moves it and releases it when it lifts, so an application
written for a pointer works on a phone as it is.

implementations/Crafter.Graphics-Device.cpp

@@ -546,12 +546,82 @@ void Device::TickKeyRepeats() {
     }
 }
 
+// The first finger stands in for the pointer: it enters the window (so the
+// clipboard has a serial and Device::focusedWindow a window), presses the
+// left button, moves it and releases it. Every finger is also reported as
+// such, in physical pixels.
+void Device::touch_down(void*, wl_touch*, std::uint32_t serial, std::uint32_t, wl_surface* surface, std::int32_t id, wl_fixed_t x, wl_fixed_t y) {
+    Window* window = nullptr;
+    for (Window* candidate : windows) {
+        if (candidate->surface == surface) window = candidate;
+    }
+    if (window == nullptr) return;
+    touchWindow = window;
+    window->lastPointerSerial_ = serial;
+    const Vector<float, 2> pos = Vector<float, 2>(wl_fixed_to_double(x), wl_fixed_to_double(y)) * window->scale;
+    touchPositions[id] = { pos.x, pos.y };
+    window->onTouchDown.Invoke({ id, pos });
+    if (window->primaryTouchId < 0) {
+        window->primaryTouchId = id;
+        focusedWindow = window;
+        window->currentMousePos = pos;
+        window->mouseLeftHeld = true;
+        window->onMouseLeftClick.Invoke();
+    }
+}
+
+void Device::touch_up(void*, wl_touch*, std::uint32_t, std::uint32_t, std::int32_t id) {
+    if (touchWindow == nullptr) return;
+    Window* window = touchWindow;
+    const auto at = touchPositions.find(id);
+    const Vector<float, 2> pos = at == touchPositions.end() ? window->currentMousePos : Vector<float, 2>(at->second.first, at->second.second);
+    touchPositions.erase(id);
+    window->onTouchUp.Invoke({ id, pos });
+    if (id == window->primaryTouchId) {
+        window->primaryTouchId = -1;
+        window->mouseLeftHeld = false;
+        window->onMouseLeftRelease.Invoke();
+    }
+    if (touchPositions.empty()) touchWindow = nullptr;
+}
+
+void Device::touch_motion(void*, wl_touch*, std::uint32_t, std::int32_t id, wl_fixed_t x, wl_fixed_t y) {
+    if (touchWindow == nullptr) return;
+    Window* window = touchWindow;
+    const Vector<float, 2> pos = Vector<float, 2>(wl_fixed_to_double(x), wl_fixed_to_double(y)) * window->scale;
+    touchPositions[id] = { pos.x, pos.y };
+    window->onTouchMove.Invoke({ id, pos });
+    if (id == window->primaryTouchId) {
+        window->currentMousePos = pos;
+        window->onMouseMove.Invoke();
+    }
+}
+
+void Device::touch_frame(void*, wl_touch*) {}
+
+void Device::touch_cancel(void*, wl_touch*) {
+    if (touchWindow == nullptr) return;
+    Window* window = touchWindow;
+    touchPositions.clear();
+    touchWindow = nullptr;
+    if (window->primaryTouchId >= 0) {
+        window->primaryTouchId = -1;
+        window->mouseLeftHeld = false;
+        window->onMouseLeftRelease.Invoke();
+    }
+    window->onTouchCancel.Invoke();
+}
+
 void Device::seat_handle_capabilities(void* data, wl_seat* seat, uint32_t capabilities) {
 	seat = seat;
 	if (capabilities & WL_SEAT_CAPABILITY_POINTER) {
 		wl_pointer* pointer = wl_seat_get_pointer(seat);
 		wl_pointer_add_listener(pointer, &pointer_listener, nullptr);
 	}
+	if ((capabilities & WL_SEAT_CAPABILITY_TOUCH) && wlTouch == nullptr) {
+		wlTouch = wl_seat_get_touch(seat);
+		wl_touch_add_listener(wlTouch, &touch_listener, nullptr);
+	}
 	if (capabilities & WL_SEAT_CAPABILITY_KEYBOARD) {
         wl_keyboard* keyboard = wl_seat_get_keyboard(seat);
         wl_keyboard_add_listener(keyboard, &keyboard_listener, nullptr);

implementations/Crafter.Graphics-Window.cpp

@@ -557,6 +557,10 @@ Window::~Window() {
     std::erase(Device::windows, this);
     if (Device::focusedWindow == this) Device::focusedWindow = nullptr;
     if (Device::keyboardWindow == this) Device::keyboardWindow = nullptr;
+    if (Device::touchWindow == this) {
+        Device::touchWindow = nullptr;
+        Device::touchPositions.clear();
+    }
     #endif
 }
 #endif