compositor: only reflow the outputs if the shell did not move them

weston_compositor_reflow_outputs() assumes that all output are positioned from
left to right with no gaps in the same order in which they where created.

If the shell moves an output with weston_output_move() then this assumption is
no longer true. So stop reflowing the outputs in the case. The shell is now
responsible for positioning all outputs as needed.

Signed-off-by: Michael Olbrich <m.olbrich@pengutronix.de>

include/libweston/libweston.h

@@ -1263,6 +1263,7 @@ struct weston_compositor {
 	struct wl_list plugin_api_list; /* struct weston_plugin_api::link */
 
 	uint32_t output_id_pool;
+	bool output_flow_dirty;
 
 	struct xkb_rule_names xkb_names;
 	struct xkb_context *xkb_context;

libweston/compositor.c

@@ -6253,6 +6253,9 @@ weston_head_get_destroy_listener(struct weston_head *head,
 	return wl_signal_get(&head->destroy_signal, notify);
 }
 
+static void
+weston_output_set_position(struct weston_output *output, int x, int y);
+
 /* Move other outputs when one is resized so the space remains contiguous. */
 static void
 weston_compositor_reflow_outputs(struct weston_compositor *compositor,
@@ -6261,6 +6264,9 @@ weston_compositor_reflow_outputs(struct weston_compositor *compositor,
 	struct weston_output *output;
 	bool start_resizing = false;
 
+	if (compositor->output_flow_dirty)
+		return;
+
 	if (!delta_width)
 		return;
 
@@ -6271,7 +6277,7 @@ weston_compositor_reflow_outputs(struct weston_compositor *compositor,
 		}
 
 		if (start_resizing) {
-			weston_output_move(output, output->x + delta_width, output->y);
+			weston_output_set_position(output, output->x + delta_width, output->y);
 			output->dirty = 1;
 		}
 	}
@@ -6377,8 +6383,8 @@ weston_output_init_geometry(struct weston_output *output, int x, int y)
 /**
  * \ingroup output
  */
-WL_EXPORT void
-weston_output_move(struct weston_output *output, int x, int y)
+static void
+weston_output_set_position(struct weston_output *output, int x, int y)
 {
 	struct weston_head *head;
 	struct wl_resource *resource;
@@ -6424,6 +6430,16 @@ weston_output_move(struct weston_output *output, int x, int y)
 	}
 }
 
+/**
+ * \ingroup output
+ */
+WL_EXPORT void
+weston_output_move(struct weston_output *output, int x, int y)
+{
+	output->compositor->output_flow_dirty = true;
+	weston_output_set_position(output, x, y);
+}
+
 /** Signal that a pending output is taken into use.
  *
  * Removes the output from the pending list and adds it to the compositor's