rootston/layer_shell: fix clicking after surface moved/resized

Layer surfaces are not notified of cursor position changes if the surface moves, only if the cursor moves. This workaround emits a cursor position event every time a cursor ends up over a newly resized layer surface to make sure the following clicks land in the right place.

This change doesn't address sending leave events when a cursor previously present over the surface becomes away.

There are 2 separate mechanisms in play, because a layer surface gets resized in 2 steps:

1. Layer surface resize & rearrange.
2. Underlying surface resize.

The first step may affect all layer surfaces. The cursor events are sent to cursors placed over all layer surfaces which have moved (not been resized). The second step affects any layer surface whose surface changed size. The cursor event is sent only to that surface.

Together, these events cover all surfaces: those which moves, and those which changed size, as long as each layer surface resize is accompanied by an immediate surface resize.

rootston/layer_shell.c

@@ -1,6 +1,12 @@
+#ifndef _POSIX_C_SOURCE
+#define _POSIX_C_SOURCE 200112L
+#endif
 #include <assert.h>
+#include <errno.h>
 #include <stdbool.h>
 #include <stdlib.h>
+#include <string.h>
+#include <time.h>
 #include <wayland-server.h>
 #include <wlr/types/wlr_box.h>
 #include <wlr/types/wlr_surface.h>
@@ -73,7 +79,32 @@ static void apply_exclusive(struct wlr_box *usable_area,
 	}
 }
 
-static void arrange_layer(struct wlr_output *output, struct wl_list *list,
+static void update_cursors(struct roots_layer_surface *roots_surface,
+		struct wl_list *seats /* struct roots_seat */) {
+	struct roots_seat *seat;
+	wl_list_for_each(seat, seats, link) {
+		double sx, sy;
+
+		struct wlr_surface *surface = desktop_surface_at(
+			seat->input->server->desktop,
+			seat->cursor->cursor->x, seat->cursor->cursor->y, &sx, &sy, NULL);
+
+		if (surface == roots_surface->layer_surface->surface) {
+			struct timespec time;
+			if (clock_gettime(CLOCK_MONOTONIC, &time) == 0) {
+				roots_cursor_update_position(seat->cursor,
+					time.tv_sec * 1000 + time.tv_nsec / 1000000);
+			} else {
+				wlr_log(WLR_ERROR, "Failed to get time, not updating"
+					"position. Errno: %s\n", strerror(errno));
+			}
+		}
+	}
+}
+
+static void arrange_layer(struct wlr_output *output,
+		struct wl_list *seats /* struct *roots_seat */,
+		struct wl_list *list /* struct *roots_layer_surface */,
 		struct wlr_box *usable_area, bool exclusive) {
 	struct roots_layer_surface *roots_surface;
 	struct wlr_box full_area = { 0 };
@@ -143,12 +174,25 @@ static void arrange_layer(struct wlr_output *output, struct wl_list *list,
 			wlr_layer_surface_close(layer);
 			continue;
 		}
+
 		// Apply
+		struct wlr_box old_geo = roots_surface->geo;
 		roots_surface->geo = box;
 		apply_exclusive(usable_area, state->anchor, state->exclusive_zone,
 				state->margin.top, state->margin.right,
 				state->margin.bottom, state->margin.left);
 		wlr_layer_surface_configure(layer, box.width, box.height);
+
+		// Having a cursor newly end up over the moved layer will not
+		// automatically send a motion event to the surface. The event needs to
+		// be synthesized.
+		// Only update layer surfaces which kept their size (and so buffers) the
+		// same, because those with resized buffers will be handled separately.
+
+		if (roots_surface->geo.x != old_geo.x
+				|| roots_surface->geo.y != old_geo.y) {
+			update_cursors(roots_surface, seats);
+		}
 	}
 }
 
@@ -158,16 +202,16 @@ void arrange_layers(struct roots_output *output) {
 			&usable_area.width, &usable_area.height);
 
 	// Arrange exclusive surfaces from top->bottom
-	arrange_layer(output->wlr_output,
+	arrange_layer(output->wlr_output, &output->desktop->server->input->seats,
 			&output->layers[ZWLR_LAYER_SHELL_V1_LAYER_OVERLAY],
 			&usable_area, true);
-	arrange_layer(output->wlr_output,
+	arrange_layer(output->wlr_output, &output->desktop->server->input->seats,
 			&output->layers[ZWLR_LAYER_SHELL_V1_LAYER_TOP],
 			&usable_area, true);
-	arrange_layer(output->wlr_output,
+	arrange_layer(output->wlr_output, &output->desktop->server->input->seats,
 			&output->layers[ZWLR_LAYER_SHELL_V1_LAYER_BOTTOM],
 			&usable_area, true);
-	arrange_layer(output->wlr_output,
+	arrange_layer(output->wlr_output, &output->desktop->server->input->seats,
 			&output->layers[ZWLR_LAYER_SHELL_V1_LAYER_BACKGROUND],
 			&usable_area, true);
 	memcpy(&output->usable_area, &usable_area, sizeof(struct wlr_box));
@@ -180,16 +224,16 @@ void arrange_layers(struct roots_output *output) {
 	}
 
 	// Arrange non-exlusive surfaces from top->bottom
-	arrange_layer(output->wlr_output,
+	arrange_layer(output->wlr_output, &output->desktop->server->input->seats,
 			&output->layers[ZWLR_LAYER_SHELL_V1_LAYER_OVERLAY],
 			&usable_area, false);
-	arrange_layer(output->wlr_output,
+	arrange_layer(output->wlr_output, &output->desktop->server->input->seats,
 			&output->layers[ZWLR_LAYER_SHELL_V1_LAYER_TOP],
 			&usable_area, false);
-	arrange_layer(output->wlr_output,
+	arrange_layer(output->wlr_output, &output->desktop->server->input->seats,
 			&output->layers[ZWLR_LAYER_SHELL_V1_LAYER_BOTTOM],
 			&usable_area, false);
-	arrange_layer(output->wlr_output,
+	arrange_layer(output->wlr_output, &output->desktop->server->input->seats,
 			&output->layers[ZWLR_LAYER_SHELL_V1_LAYER_BACKGROUND],
 			&usable_area, false);
 
@@ -238,6 +282,20 @@ static void handle_surface_commit(struct wl_listener *listener, void *data) {
 		struct roots_output *output = wlr_output->data;
 		struct wlr_box old_geo = layer->geo;
 		arrange_layers(output);
+
+		// Cursor changes which happen as a consequence of resizing a layer
+		// surface are applied in arrange_layers. Because the resize happens
+		// before the underlying surface changes, it will only receive a cursor
+		// update if the new cursor position crosses the *old* sized surface in
+		// the *new* layer surface.
+		// Another cursor move event is needed when the surface actually
+		// changes.
+		struct wlr_surface *surface = layer_surface->surface;
+		if (surface->previous.width != surface->current.width ||
+				surface->previous.height != surface->current.height) {
+			update_cursors(layer, &output->desktop->server->input->seats);
+		}
+
 		if (memcmp(&old_geo, &layer->geo, sizeof(struct wlr_box)) != 0) {
 			output_damage_whole_local_surface(output, layer_surface->surface,
 					old_geo.x, old_geo.y, 0);