backend-drm/state-propose: Check the surface buffer dimensions for cursor case

In some situations, like positioning a sub-surface that exceeds the
output's dimensions we would adjust the plane state dimensions to some
lower values to that of the buffer. That would ultimately trip the cursor
update function because the buffer itself actually exceeds the maximum
size/dimension of the cursor.

The plane state destination co-ordinates is the area of the view which
is visible on the output, which in some situations, would actually be
smaller than the original buffer dimensions (making it so that it will
pass the cropping/scaling check), but depending on of
how large is the surface buffer, it would tripping the assert wrt to
cursor width/height dimensions.

This hasn't been seen so far due to the fact that until recently we had
a cursor surface that always reached the cursor plane and that was
already being set-up by default (with desktop-shell, which is no longer
the case), and also because kiosk-shell, which doesn't set-up a cursor
surface, was not available.

This adds a check to skip placing the view in the cursor plane if the
buffer dimensions exceed the cursor permitted width/height.
(Suggested-by Daniel Stone).

Signed-off-by: Marius Vlad <marius.vlad@collabora.com>

libweston/backend-drm/state-propose.c

@@ -306,6 +306,7 @@ drm_output_prepare_cursor_view(struct drm_output_state *output_state,
 	struct drm_plane *plane = output->cursor_plane;
 	struct drm_plane_state *plane_state;
 	bool needs_update = false;
+	struct weston_buffer *buffer = ev->surface->buffer_ref.buffer;
 	const char *p_name = drm_output_get_plane_type_name(plane);
 
 	assert(!b->cursors_are_broken);
@@ -337,6 +338,16 @@ drm_output_prepare_cursor_view(struct drm_output_state *output_state,
 		goto err;
 	}
 
+	if (buffer->width > b->cursor_width ||
+	    buffer->height > b->cursor_height) {
+		drm_debug(b, "\t\t\t\t[%s] not assigning view %p to %s plane "
+			     "(surface buffer (%dx%d) larger than permitted"
+			     " (%dx%d))\n", p_name, ev, p_name,
+			     buffer->width, buffer->height,
+			     b->cursor_width, b->cursor_height);
+		goto err;
+	}
+
 	if (plane_state->src_x != 0 || plane_state->src_y != 0 ||
 	    plane_state->src_w > (unsigned) b->cursor_width << 16 ||
 	    plane_state->src_h > (unsigned) b->cursor_height << 16 ||