zoom: Store the seat that initiated a zoom

Track the seat that initiated a seat instead of picking the first one.

Previously, if there are multiple seats then any seat can adjust the zoom
level but the zoom tracks the first seat's pointer.

Now the zoom will follow the pointer of the seat that initiated the zoom.

Additionally, if there's no pointer in the first seat, starting a zoom
with the second seat will no longer crash weston.

Signed-off-by: Derek Foreman <derekf@osg.samsung.com>

desktop-shell/shell.c

@@ -4808,7 +4808,7 @@ do_zoom(struct weston_seat *seat, uint32_t time, uint32_t key, uint32_t axis,
 			if (!output->zoom.active) {
 				if (output->zoom.level <= 0.0)
 					continue;
-				weston_output_activate_zoom(output);
+				weston_output_activate_zoom(output, seat);
 			}
 
 			output->zoom.spring_z.target = output->zoom.level;

src/compositor.h

@@ -152,6 +152,7 @@ struct weston_output_zoom {
 	float level;
 	float max_level;
 	float trans_x, trans_y;
+	struct weston_seat *seat;
 	struct weston_animation animation_z;
 	struct weston_spring spring_z;
 	struct weston_fixed_point current;
@@ -1370,7 +1371,8 @@ weston_output_init_zoom(struct weston_output *output);
 void
 weston_output_update_zoom(struct weston_output *output);
 void
-weston_output_activate_zoom(struct weston_output *output);
+weston_output_activate_zoom(struct weston_output *output,
+			    struct weston_seat *seat);
 void
 weston_output_update_matrix(struct weston_output *output);
 void

src/zoom.c

@@ -50,6 +50,7 @@ weston_zoom_frame_z(struct weston_animation *animation,
 	if (weston_spring_done(&output->zoom.spring_z)) {
 		if (output->zoom.active && output->zoom.level <= 0.0) {
 			output->zoom.active = false;
+			output->zoom.seat = NULL;
 			output->disable_planes--;
 			wl_list_remove(&output->zoom.motion_listener.link);
 		}
@@ -62,13 +63,6 @@ weston_zoom_frame_z(struct weston_animation *animation,
 	weston_output_damage(output);
 }
 
-static struct weston_seat *
-weston_zoom_pick_seat(struct weston_compositor *compositor)
-{
-	return container_of(compositor->seat_list.next,
-			    struct weston_seat, link);
-}
-
 static void
 zoom_area_center_from_point(struct weston_output *output,
 			    wl_fixed_t *x, wl_fixed_t *y)
@@ -134,7 +128,7 @@ weston_zoom_transition(struct weston_output *output)
 WL_EXPORT void
 weston_output_update_zoom(struct weston_output *output)
 {
-	struct weston_seat *seat = weston_zoom_pick_seat(output->compositor);
+	struct weston_seat *seat = output->zoom.seat;
 
 	assert(output->zoom.active);
 
@@ -157,14 +151,14 @@ motion(struct wl_listener *listener, void *data)
 }
 
 WL_EXPORT void
-weston_output_activate_zoom(struct weston_output *output)
+weston_output_activate_zoom(struct weston_output *output,
+			    struct weston_seat *seat)
 {
-	struct weston_seat *seat = weston_zoom_pick_seat(output->compositor);
-
 	if (output->zoom.active)
 		return;
 
 	output->zoom.active = true;
+	output->zoom.seat = seat;
 	output->disable_planes++;
 	wl_signal_add(&seat->pointer->motion_signal,
 		      &output->zoom.motion_listener);
@@ -174,6 +168,7 @@ WL_EXPORT void
 weston_output_init_zoom(struct weston_output *output)
 {
 	output->zoom.active = false;
+	output->zoom.seat = NULL;
 	output->zoom.increment = 0.07;
 	output->zoom.max_level = 0.95;
 	output->zoom.level = 0.0;