File 0001-Drop-wayland-client.h-include.patch of Package vulkan-headers

From 898bd798e823e7708e4dbeb07955ae2ee17f925a Mon Sep 17 00:00:00 2001
From: Jan Engelhardt <jengelh@inai.de>
Date: Tue, 12 Jul 2022 17:10:18 +0200
Subject: [PATCH] Drop wayland-client.h include
Upstream: not sent
References: https://build.opensuse.org/package/show/X11:Wayland/vulkan-loader comment from 2022-07-12

wayland-client may be located outside the default search paths of the compiler
toolchain. In other words, *any* user of wayland-client must use `pkg-config
wayland-client --cflags` for compilation, and, later, `pkg-config
wayland-client --libs` for linking.

A Vulkan program that defines -DVK_USE_PLATFORM_WAYLAND_KHR would, in
the general case, also call at least some Wayland functions. The
build scripts for that program would have to employ `pkg-config
wayland-client --cflags --libs` in any case, based simply on the use
of said Wayland functions.

Now, there is a corner case wherein the program defines
VK_USE_PLATFORM_*, but does not make use of Wayland functions
directly:

	echo "#define VK_USE_PLATFORM_WAYLAND_KHR
	#include <vulkan/vulkan.h>
	int main() {return 0;}" | gcc -x c -

"Should `pkg-config` be required for this?"

One opinion is that the use of -DVK_USE_PLATFORM_WAYLAND_KHR is so
explicitly willful that `pkg-config` is required.

Another stance is that, since no Wayland header and no Wayland
functions were directly used by the program, the program itself
should not have to use `pkg-config`; responsibility to satisfy the
"#include <wayland-client.h>" in vulkan.h would then fall to
vulkan.pc, which would have to pull in wayland-client.pc. That on the
other hand would pull in wayland for everyone, which is bad.

Either way, I found the following option: Delete the include for
which you would need wayland's -I flags. This works because we can
just add forward declaration like "struct wl_display;" to
vulkan_wayland.h. But we don't even need that. C (and C++) seem to be
fine with undeclared names, e.g.

	//no "struct T;"
	struct S { struct T *t; }
	void f(struct T *t) {}

so I guess it's the solution, for now.

Keep in mind that, as soon as a program uses Wayland functions (directly; not
indirectly through vulkan), it needs to #include <wayland-client.h> anyway on
its own, and then the pkg-config case from the first paragraph applies.

---
 include/vulkan/vulkan.h | 1 -
 1 file changed, 1 deletion(-)

diff --git a/include/vulkan/vulkan.h b/include/vulkan/vulkan.h
index 004fa70..3510ac9 100644
--- a/include/vulkan/vulkan.h
+++ b/include/vulkan/vulkan.h
@@ -38,7 +38,6 @@
 
 
 #ifdef VK_USE_PLATFORM_WAYLAND_KHR
-#include <wayland-client.h>
 #include "vulkan_wayland.h"
 #endif
 
-- 
2.36.1