gl-renderer: Rename buffer_damage variable

The buffer_damage variable stores accumulated damage from previous
frames. This is the area that, before considering our current repaint
request, we need to repaint in order to bring the older buffer up to
date with the last buffer we rendered into.

Rename to previous_damage so it's a bit more clear what this refers to.

Signed-off-by: Daniel Stone <daniels@collabora.com>

libweston/renderer-gl/gl-renderer.c

@@ -1434,7 +1434,10 @@ gl_renderer_repaint_output(struct weston_output *output,
 	struct gl_renderer *gr = get_renderer(compositor);
 	EGLBoolean ret;
 	static int errored;
-	pixman_region32_t buffer_damage, total_damage;
+	/* areas we've damaged since we last used this buffer */
+	pixman_region32_t previous_damage;
+	/* total area we need to repaint this time */
+	pixman_region32_t total_damage;
 	enum gl_border_status border_status = BORDER_STATUS_CLEAN;
 	struct weston_view *view;
 
@@ -1489,18 +1492,18 @@ gl_renderer_repaint_output(struct weston_output *output,
 	}
 
 	pixman_region32_init(&total_damage);
-	pixman_region32_init(&buffer_damage);
+	pixman_region32_init(&previous_damage);
 
-	output_get_damage(output, &buffer_damage, &border_status);
+	output_get_damage(output, &previous_damage, &border_status);
 	output_rotate_damage(output, output_damage, go->border_status);
 
-	pixman_region32_union(&total_damage, &buffer_damage, output_damage);
+	pixman_region32_union(&total_damage, &previous_damage, output_damage);
 	border_status |= go->border_status;
 
 	repaint_views(output, &total_damage);
 
 	pixman_region32_fini(&total_damage);
-	pixman_region32_fini(&buffer_damage);
+	pixman_region32_fini(&previous_damage);
 
 	draw_output_borders(output, border_status);