From dad7312814ed6ed014c51e2c72a0429399cfad73 Mon Sep 17 00:00:00 2001
From: Andri Yngvason <andri@yngvason.is>
Date: Sun, 19 Sep 2021 19:54:23 +0000
Subject: [PATCH] pixels: Add fourcc_to_pixman_fmt

---
 include/pixels.h |  6 ++++-
 src/pixels.c     | 69 ++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 74 insertions(+), 1 deletion(-)

diff --git a/include/pixels.h b/include/pixels.h
index 3ebd1d9..aa4c9ad 100644
--- a/include/pixels.h
+++ b/include/pixels.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2019 Andri Yngvason
+ * Copyright (c) 2019 - 2021 Andri Yngvason
  *
  * Permission to use, copy, modify, and/or distribute this software for any
  * purpose with or without fee is hereby granted, provided that the above
@@ -18,6 +18,8 @@
 
 #include <stdint.h>
 #include <unistd.h>
+#include <pixman.h>
+#include <stdbool.h>
 
 struct rfb_pixel_format;
 
@@ -31,3 +33,5 @@ int rfb_pixfmt_from_fourcc(struct rfb_pixel_format *dst, uint32_t src);
 uint32_t rfb_pixfmt_to_fourcc(const struct rfb_pixel_format* fmt);
 
 int pixel_size_from_fourcc(uint32_t fourcc);
+
+bool fourcc_to_pixman_fmt(pixman_format_code_t* dst, uint32_t src);
diff --git a/src/pixels.c b/src/pixels.c
index 9b25909..ad7d2ff 100644
--- a/src/pixels.c
+++ b/src/pixels.c
@@ -247,3 +247,72 @@ int pixel_size_from_fourcc(uint32_t fourcc)
 
 	return 0;
 }
+
+bool fourcc_to_pixman_fmt(pixman_format_code_t* dst, uint32_t src)
+{
+	assert(!(src & DRM_FORMAT_BIG_ENDIAN));
+
+#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_DRM(x, y, z, v, a, b, c, d) DRM_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_DRM(__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,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;
+}