backend/wayland: add support for relative-pointer-unstable-v1

We just send relative motion events alongside absolute motion events.
Compositors can figure out how absolute and relative events are related
(e.g. whether they have been triggered by the same logical event) with
the frame event.

backend/wayland/backend.c

@@ -22,6 +22,7 @@
 #include "xdg-decoration-unstable-v1-client-protocol.h"
 #include "xdg-shell-client-protocol.h"
 #include "tablet-unstable-v2-client-protocol.h"
+#include "relative-pointer-unstable-v1-client-protocol.h"
 
 struct wlr_wl_backend *get_wl_backend_from_backend(struct wlr_backend *backend) {
 	assert(wlr_backend_is_wl(backend));
@@ -116,6 +117,9 @@ static void registry_global(void *data, struct wl_registry *registry,
 			&zwp_linux_dmabuf_v1_interface, 3);
 		zwp_linux_dmabuf_v1_add_listener(wl->zwp_linux_dmabuf_v1,
 			&linux_dmabuf_v1_listener, wl);
+	} else if (strcmp(iface, zwp_relative_pointer_manager_v1_interface.name) == 0) {
+		wl->zwp_relative_pointer_manager_v1 = wl_registry_bind(registry, name,
+			&zwp_relative_pointer_manager_v1_interface, 1);
 	}
 }
 
@@ -201,6 +205,9 @@ static void backend_destroy(struct wlr_backend *backend) {
 	if (wl->zwp_linux_dmabuf_v1) {
 		zwp_linux_dmabuf_v1_destroy(wl->zwp_linux_dmabuf_v1);
 	}
+	if (wl->zwp_relative_pointer_manager_v1) {
+		zwp_relative_pointer_manager_v1_destroy(wl->zwp_relative_pointer_manager_v1);
+	}
 	xdg_wm_base_destroy(wl->xdg_wm_base);
 	wl_compositor_destroy(wl->compositor);
 	wl_registry_destroy(wl->registry);

backend/wayland/wl_seat.c

@@ -16,6 +16,7 @@
 #include <wlr/util/log.h>
 
 #include "pointer-gestures-unstable-v1-client-protocol.h"
+#include "relative-pointer-unstable-v1-client-protocol.h"
 #include "backend/wayland.h"
 #include "util/signal.h"
 
@@ -446,6 +447,31 @@ static struct zwp_pointer_gesture_pinch_v1_listener gesture_pinch_impl = {
 };
 
 
+void relative_pointer_handle_relative_motion(void *data,
+		struct zwp_relative_pointer_v1 *relative_pointer, uint32_t utime_hi,
+		uint32_t utime_lo, wl_fixed_t dx, wl_fixed_t dy, wl_fixed_t dx_unaccel,
+		wl_fixed_t dy_unaccel) {
+	struct wlr_wl_input_device *input_device = data;
+	struct wlr_input_device *wlr_dev = &input_device->wlr_input_device;
+
+	uint64_t time_usec = (uint64_t)utime_hi << 32 | utime_lo;
+
+	struct wlr_event_pointer_motion wlr_event = {
+		.device = wlr_dev,
+		.time_msec = (uint32_t)(time_usec / 1000),
+		.delta_x = wl_fixed_to_double(dx),
+		.delta_y = wl_fixed_to_double(dy),
+		.unaccel_dx = wl_fixed_to_double(dx_unaccel),
+		.unaccel_dy = wl_fixed_to_double(dy_unaccel),
+	};
+	wlr_signal_emit_safe(&wlr_dev->pointer->events.motion, &wlr_event);
+}
+
+static const struct zwp_relative_pointer_v1_listener relative_pointer_listener = {
+	.relative_motion = relative_pointer_handle_relative_motion,
+};
+
+
 static void pointer_handle_output_destroy(struct wl_listener *listener,
 		void *data) {
 	struct wlr_wl_pointer *pointer =
@@ -501,6 +527,14 @@ void create_wl_pointer(struct wl_pointer *wl_pointer, struct wlr_wl_output *outp
 		zwp_pointer_gesture_pinch_v1_add_listener(pointer->gesture_pinch, &gesture_pinch_impl, dev);
 	}
 
+	if (backend->zwp_relative_pointer_manager_v1) {
+		pointer->relative_pointer =
+			zwp_relative_pointer_manager_v1_get_relative_pointer(
+			backend->zwp_relative_pointer_manager_v1, wl_pointer);
+		zwp_relative_pointer_v1_add_listener(pointer->relative_pointer,
+			&relative_pointer_listener, dev);
+	}
+
 	wlr_signal_emit_safe(&backend->backend.events.new_input, wlr_dev);
 }
 

include/backend/wayland.h

@@ -36,6 +36,7 @@ struct wlr_wl_backend {
 	struct zxdg_decoration_manager_v1 *zxdg_decoration_manager_v1;
 	struct zwp_pointer_gestures_v1 *zwp_pointer_gestures_v1;
 	struct zwp_linux_dmabuf_v1 *zwp_linux_dmabuf_v1;
+	struct zwp_relative_pointer_manager_v1 *zwp_relative_pointer_manager_v1;
 	struct wl_seat *seat;
 	struct wl_pointer *pointer;
 	struct wl_keyboard *keyboard;
@@ -86,6 +87,7 @@ struct wlr_wl_pointer {
 	struct wl_pointer *wl_pointer;
 	struct zwp_pointer_gesture_swipe_v1 *gesture_swipe;
 	struct zwp_pointer_gesture_pinch_v1 *gesture_pinch;
+	struct zwp_relative_pointer_v1 *relative_pointer;
 	enum wlr_axis_source axis_source;
 	int32_t axis_discrete;
 	struct wlr_wl_output *output;