Autotools build doesn't actually enable X11

[bochecha]

ce8cbdb made X11 optional for both the Autotools and Meson builds.

In src/dispatch_common.h, we can see:

# if !ENABLE_X11
/* Mesa uses this symbol to avoid including X11 headers when including
 * EGL.h; since X11 was explicitly disabled at configuration time, we
 * should do the same
 */
#  define MESA_EGL_NO_X11_HEADERS 1
# endif

Unfortunately, the Autotools build never sets ENABLE_X11, even when --enable-x11 was passed, and the dependencies are installed.

So the resulting build is missing some X11 support.

This causes an ABI break when moving from an Autotools build to a Meson one:

Functions changes summary: 0 Removed, 0 Changed, 0 Added function
Variables changes summary: 0 Removed, 2 Changed (5 filtered out), 0 Added variables

2 Changed variables:

  [C]'typedef EGLDisplay (typedef EGLNativeDisplayType)* epoxy_eglGetDisplay' was changed at egl_generated.h:991:1:
    type of variable changed:
     in pointed to type 'function type typedef EGLDisplay (typedef EGLNativeDisplayType)':
       parameter 1 of type 'typedef EGLNativeDisplayType' changed:
         underlying type 'void*' changed:
           in pointed to type 'void' at Xlib.h:487:1:
             entity changed from 'void' to 'typedef Display' at Xlib.h:487:1
             type size hasn't changed

  [C]'typedef EGLBoolean (typedef EGLDisplay, EGLNativeDisplayType*)* epoxy_eglQueryNativeDisplayNV' was changed at egl_generated.h:1063:1:
    type of variable changed:
     in pointed to type 'function type typedef EGLBoolean (typedef EGLDisplay, EGLNativeDisplayType*)':
       parameter 2 of type 'EGLNativeDisplayType*' changed:
         pointed to type 'typedef EGLNativeDisplayType' changed at eglplatform.h:117:1, as reported earlier

This is when compiling 1.5.2, but I think master is affected in the same way.

Big thanks to @cfergeau for putting me on the right track.

[ebassi]

Thanks for the detective work! We're only ever testing the Meson build in the CI, so it slipped through the cracks.

Could you please test #193 and see if it works? I'd like to get this merged for 1.5.3.