vo_opengl: angle: dynamically load ANGLE

ANGLE is _really_ annoying to build. (Requires special toolchain and a
recent MSVC version.) This results in various issues with people
having trouble to build mpv against ANGLE (apparently linking it
against a prebuilt binary doesn't count, or using binaries from
potentially untrusted sources is not wanted).

Dynamically loading ANGLE is going to be a huge convenience. This commit
implements this, with special focus on keeping it source compatible to
a normal build with ANGLE linked at build-time.

1 files changed, 2 insertions, 3 deletions

diff --git a/wscript b/wscript
index d4f84e13b4..0a031aac81 100644
--- a/wscript
+++ b/wscript
@@ -699,9 +699,8 @@ video_output_features = [
         'desc': 'OpenGL Win32 ANGLE Backend',
         'deps_any': [ 'os-win32', 'os-cygwin' ],
         'groups': [ 'gl' ],
-        'func': check_statement(['EGL/egl.h'],
-                                'eglCreateWindowSurface(0, 0, 0, 0)',
-                                lib='EGL')
+        'func': check_statement(['EGL/egl.h', 'EGL/eglext.h'],
+                                'int x = EGL_D3D_TEXTURE_2D_SHARE_HANDLE_ANGLE')
     } , {
         'name': '--vdpau',
         'desc': 'VDPAU acceleration',