Add make_shadow and paint_all_new to backend_common.c

Also made make_shadow private in render.c

Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>

src/backend/backend_common.h

@@ -1,6 +1,13 @@
 #pragma once
 #include <xcb/xcb_image.h>
-#include "common.h"
+#include <xcb/render.h>
+
+#include <stdbool.h>
+
+#include "region.h"
+
+typedef struct session session_t;
+typedef struct win win;
 
 bool build_shadow(session_t *ps, double opacity, const int width, const int height,
                   xcb_render_picture_t shadow_pixel, xcb_pixmap_t *pixmap,
@@ -8,3 +15,5 @@ bool build_shadow(session_t *ps, double opacity, const int width, const int heig
 
 xcb_render_picture_t
 solid_picture(session_t *ps, bool argb, double a, double r, double g, double b);
+
+void paint_all_new(session_t *ps, region_t *region, win *const t);