compositor-drm: Split cursor handling into prepare and set

Like how we handle overlays, we split drm_output_set_cursor() into
drm_output_prepare_cursor_surface() that will assign the hw cursor to
a suitable surface and drm_output_set_cursor() that will do the actual
work of updating cursor contents and moving it.  This is more in line
with how we handle everything else, and lets us update cursor contents
based on changes to the cursor plane damage.

This works when the cursor content changes but also accumulates
damage when the cursor changes output.  In that case we move the
cursor surface to the cursor plane in the new output and
weston_surface_move_to_plane() will generate the damage that triggers
download of sprite contents there.

src/compositor-drm.c

@@ -125,7 +125,8 @@ struct drm_output {
 	struct gbm_bo *cursor_bo[2];
 	struct weston_plane cursor_plane;
 	struct weston_plane fb_plane;
-	int current_cursor, cursor_free;
+	struct weston_surface *cursor_surface;
+	int current_cursor;
 	EGLSurface egl_surface;
 	struct drm_fb *current, *next;
 	struct backlight *backlight;
@@ -163,6 +164,11 @@ struct drm_sprite {
 	uint32_t formats[];
 };
 
+static void
+drm_output_set_cursor(struct drm_output *output);
+static void
+drm_disable_unused_sprites(struct weston_output *output_base);
+
 static int
 drm_sprite_crtc_supported(struct weston_output *output_base, uint32_t supported)
 {
@@ -367,6 +373,8 @@ drm_output_repaint(struct weston_output *output_base,
 
 	output->page_flip_pending = 1;
 
+	drm_output_set_cursor(output);
+
 	/*
 	 * Now, update all the sprite surfaces
 	 */
@@ -405,6 +413,8 @@ drm_output_repaint(struct weston_output *output_base,
 		output->vblank_pending = 1;
 	}
 
+	drm_disable_unused_sprites(&output->base);
+
 	return;
 }
 
@@ -683,10 +693,28 @@ drm_output_prepare_overlay_surface(struct weston_output *output_base,
 }
 
 static struct weston_plane *
-drm_output_set_cursor(struct weston_output *output_base,
+drm_output_prepare_cursor_surface(struct weston_output *output_base,
 				  struct weston_surface *es)
 {
 	struct drm_output *output = (struct drm_output *) output_base;
+
+	if (output->cursor_surface)
+		return NULL;
+	if (es->output_mask != (1u << output_base->id))
+		return NULL;
+	if (es->buffer == NULL || !wl_buffer_is_shm(es->buffer) ||
+	    es->geometry.width > 64 || es->geometry.height > 64)
+		return NULL;
+
+	output->cursor_surface = es;
+
+	return &output->cursor_plane;
+}
+
+static void
+drm_output_set_cursor(struct drm_output *output)
+{
+	struct weston_surface *es = output->cursor_surface;
 	struct drm_compositor *c =
 		(struct drm_compositor *) output->base.compositor;
 	EGLint handle, stride;
@@ -695,16 +723,14 @@ drm_output_set_cursor(struct weston_output *output_base,
 	unsigned char *s;
 	int i, x, y;
 
-	if (!output->cursor_free)
-		return NULL;
-	if (es->output_mask != (1u << output_base->id))
-		return NULL;
-	if (es->buffer == NULL || !wl_buffer_is_shm(es->buffer) ||
-	    es->geometry.width > 64 || es->geometry.height > 64)
-		return NULL;
+	if (es == NULL) {
+		drmModeSetCursor(c->drm.fd, output->crtc_id, 0, 0, 0);
+		return;
+	}
 
-	output->cursor_free = 0;
-	if (es->buffer && pixman_region32_not_empty(&es->damage)) {
+	if (es->buffer && pixman_region32_not_empty(&output->cursor_plane.damage)) {
+		pixman_region32_fini(&output->cursor_plane.damage);
+		pixman_region32_init(&output->cursor_plane.damage);
 		output->current_cursor ^= 1;
 		bo = output->cursor_bo[output->current_cursor];
 		memset(buf, 0, sizeof buf);
@@ -731,8 +757,6 @@ drm_output_set_cursor(struct weston_output *output_base,
 		output->cursor_plane.x = x;
 		output->cursor_plane.y = y;
 	}
-
-	return &output->cursor_plane;
 }
 
 static void
@@ -759,7 +783,7 @@ drm_assign_planes(struct weston_output *output)
 	 * as we do for flipping full screen surfaces.
 	 */
 	pixman_region32_init(&overlap);
-	drm_output->cursor_free = 1;
+	drm_output->cursor_surface = NULL;
 	primary = &c->base.primary_plane;
 	wl_list_for_each_safe(es, next, &c->base.surface_list, link) {
 		pixman_region32_init(&surface_overlap);
@@ -770,7 +794,7 @@ drm_assign_planes(struct weston_output *output)
 		if (pixman_region32_not_empty(&surface_overlap))
 			next_plane = primary;
 		if (next_plane == NULL)
-			next_plane = drm_output_set_cursor(output, es);
+			next_plane = drm_output_prepare_cursor_surface(output, es);
 		if (next_plane == NULL)
 			next_plane = drm_output_prepare_scanout_surface(output, es);
 		if (next_plane == NULL)
@@ -785,11 +809,6 @@ drm_assign_planes(struct weston_output *output)
 		pixman_region32_fini(&surface_overlap);
 	}
 	pixman_region32_fini(&overlap);
-
-	if (drm_output->cursor_free)
-		drmModeSetCursor(c->drm.fd, drm_output->crtc_id, 0, 0, 0);
-
-	drm_disable_unused_sprites(output);
 }
 
 static void