initial commit: maps an XDG toplevel window

shm.h

@@ -0,0 +1,24 @@
+#pragma once
+
+#include <stdbool.h>
+#include <stddef.h>
+
+#include <cairo.h>
+#include <wayland-client.h>
+
+struct buffer {
+    int width;
+    int height;
+
+    bool busy;
+    size_t size;
+    void *mmapped;
+
+    struct wl_buffer *wl_buf;
+
+    cairo_surface_t *cairo_surface;
+    cairo_t *cairo;
+};
+
+struct buffer *shm_get_buffer(struct wl_shm *shm, int width, int height);
+void shm_fini(void);