Add pixel format conversion utils

include/pixels.h

@@ -0,0 +1,7 @@
+#pragma once
+
+#include <wayland-client.h>
+#include <pixman.h>
+#include <stdbool.h>
+
+bool wl_shm_to_pixman_fmt(pixman_format_code_t* dst, enum wl_shm_format src);

meson.build

@@ -69,6 +69,7 @@ sources = [
 	'src/vnc.c',
 	'src/strlcpy.c',
 	'src/evdev-to-qnum.c',
+	'src/pixels.c',
 ]
 
 dependencies = [

src/pixels.c

@@ -0,0 +1,74 @@
+#include <wayland-client.h>
+#include <pixman.h>
+#include <stdbool.h>
+
+bool wl_shm_to_pixman_fmt(pixman_format_code_t* dst, enum wl_shm_format src)
+{
+#define LOWER_R r
+#define LOWER_G g
+#define LOWER_B b
+#define LOWER_A a
+#define LOWER_X x
+#define LOWER_
+#define LOWER(x) LOWER_##x
+
+#define CONCAT_(a, b) a ## b
+#define CONCAT(a, b) CONCAT_(a, b)
+
+#define FMT_WL_SHM(x, y, z, v, a, b, c, d) WL_SHM_FORMAT_##x##y##z##v##a##b##c##d
+
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+#define FMT_PIXMAN(x, y, z, v, a, b, c, d) \
+	CONCAT(CONCAT(CONCAT(CONCAT(CONCAT(CONCAT(CONCAT(CONCAT(\
+	PIXMAN_, LOWER(x)), a), LOWER(y)), b), LOWER(z)), c), LOWER(v)), d)
+#else
+#define FMT_PIXMAN(x, y, z, v, a, b, c, d) \
+	CONCAT(CONCAT(CONCAT(CONCAT(CONCAT(CONCAT(CONCAT(CONCAT(\
+	PIXMAN_, LOWER(v)), d), LOWER(z)), c), LOWER(y)), b), LOWER(x)), a)
+#endif
+
+	switch (src) {
+#define X(...) \
+	case FMT_WL_SHM(__VA_ARGS__): *dst = FMT_PIXMAN(__VA_ARGS__); break
+
+	/* 32 bits */
+	X(A,R,G,B,8,8,8,8);
+	X(A,B,G,R,8,8,8,8);
+	X(X,R,G,B,8,8,8,8);
+	X(X,B,G,R,8,8,8,8);
+	X(R,G,B,A,8,8,8,8);
+	X(B,G,R,A,8,8,8,8);
+	X(R,G,B,X,8,8,8,8);
+	X(B,G,R,X,8,8,8,8);
+
+	/* 24 bits */
+	X(R,G,B,,8,8,8,);
+	X(B,G,R,,8,8,8,);
+
+	/* 16 bits */
+	X(R,G,B,,5,6,5,);
+	X(B,G,R,,5,6,5,);
+
+	/* These are incompatible on big endian */
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+	X(A,R,G,B,2,10,10,10);
+	X(X,R,G,B,2,10,10,10);
+	X(A,B,G,R,2,10,10,10);
+	X(X,B,G,R,2,10,10,10);
+	X(A,R,G,B,1,5,5,5);
+	X(A,B,G,R,1,5,5,5);
+	X(X,R,G,B,1,5,5,5);
+	X(X,B,G,R,1,5,5,5);
+	X(A,R,G,B,4,4,4,4);
+	X(A,B,G,R,4,4,4,4);
+	X(X,R,G,B,4,4,4,4);
+	X(X,B,G,R,4,4,4,4);
+#endif
+
+#undef X
+
+	default: return false;
+	}
+
+	return true;
+}