src: include primary header first

This is a common practice in C projects, which simply enforces that
each header must compile cleanly without implicit dependencies on
other headers (see also the previous commit).

src/img/img-png.c

@@ -3,6 +3,7 @@
  * Copyright (C) Johan Malm 2023
  */
 #define _POSIX_C_SOURCE 200809L
+#include "img/img-png.h"
 #include <assert.h>
 #include <cairo.h>
 #include <png.h>
@@ -12,7 +13,6 @@
 #include <wlr/util/log.h>
 #include "buffer.h"
 #include "common/string-helpers.h"
-#include "img/img-png.h"
 
 /*
  * cairo_image_surface_create_from_png() does not gracefully handle non-png

src/img/img-svg.c

@@ -3,6 +3,7 @@
  * Copyright (C) Johan Malm 2023
  */
 #define _POSIX_C_SOURCE 200809L
+#include "img/img-svg.h"
 #include <cairo.h>
 #include <librsvg/rsvg.h>
 #include <stdbool.h>
@@ -11,7 +12,6 @@
 #include <wlr/util/log.h>
 #include "buffer.h"
 #include "common/string-helpers.h"
-#include "img/img-svg.h"
 #include "labwc.h"
 
 RsvgHandle *

src/img/img-xbm.c

@@ -6,6 +6,7 @@
  */
 
 #define _POSIX_C_SOURCE 200809L
+#include "img/img-xbm.h"
 #include <assert.h>
 #include <stdbool.h>
 #include <stdint.h>
@@ -14,7 +15,6 @@
 #include <string.h>
 #include <drm_fourcc.h>
 #include "img/img.h"
-#include "img/img-xbm.h"
 #include "common/grab-file.h"
 #include "common/mem.h"
 #include "common/string-helpers.h"

src/img/img-xpm.c

@@ -11,6 +11,7 @@
  * Adapted for labwc by John Lindgren, 2024
  */
 
+#include "img/img-xpm.h"
 #include <glib.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -21,7 +22,6 @@
 #include "common/buf.h"
 #include "common/graphic-helpers.h"
 #include "common/mem.h"
-#include "img/img-xpm.h"
 
 enum buf_op { op_header, op_cmap, op_body };
 

src/img/img.c

@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0-only
 
+#include "img/img.h"
 #include <assert.h>
 #include <wlr/util/log.h>
 #include "buffer.h"
@@ -9,7 +10,6 @@
 #include "common/macros.h"
 #include "common/mem.h"
 #include "common/string-helpers.h"
-#include "img/img.h"
 #include "img/img-png.h"
 #if HAVE_RSVG
 #include "img/img-svg.h"