[gtk/wip/fanc999/gtk-3-24-meson-msvc: 29/37] meson: Enable GLES Windows builds via libANGLE

[Chun-wei Fan <fanchunwei src gnome org>]

commit 2e0b27ac5b55c964516b8c66e9c53d20c4082649
Author: Chun-wei Fan <fanchunwei src gnome org>
Date:   Wed Mar 13 15:32:14 2019 +0800

    meson: Enable GLES Windows builds via libANGLE
    
    Check whether the libepoxy library is built on Windows with support for
    GLES.  If so, enable GLES/EGL support on Windows as well.

 gdk/win32/meson.build |  9 ++++++++-
 meson.build           | 17 +++++++++++++++++
 2 files changed, 25 insertions(+), 1 deletion(-)
---
diff --git a/gdk/win32/meson.build b/gdk/win32/meson.build
index 343a9ff402..15043a9a1d 100644
--- a/gdk/win32/meson.build
+++ b/gdk/win32/meson.build
@@ -35,6 +35,13 @@ gdk_win32_public_headers = files(
   'gdkwin32window.h',
 )
 
+GDK_WIN32_CFLAGS = ['-DGDK_COMPILATION', '-DG_LOG_DOMAIN="Gdk"', '-DINSIDE_GDK_WIN32']
+
+if win32_has_egl
+  GDK_WIN32_CFLAGS += '-DGDK_WIN32_ENABLE_EGL'
+endif
+
+
 install_headers(gdk_win32_public_headers, subdir: 'gtk-3.0/gdk/win32')
 install_headers('gdkwin32.h', subdir: 'gtk-3.0/gdk')
 
@@ -44,5 +51,5 @@ gdk_win32_deps = [ # FIXME
 libgdk_win32 = static_library('gdk-win32',
   gdk_win32_sources, gdkconfig, gdkenum_h,
   include_directories: [confinc, gdkinc],
-  c_args: ['-DGDK_COMPILATION', '-DG_LOG_DOMAIN="Gdk"', '-DINSIDE_GDK_WIN32'],
+  c_args: GDK_WIN32_CFLAGS,
   dependencies: [gdk_deps, gdk_win32_deps])
diff --git a/meson.build b/meson.build
index 7077d3e58d..ba84a966f4 100644
--- a/meson.build
+++ b/meson.build
@@ -586,6 +586,23 @@ if win32_enabled
   endif
   pc_gdk_extra_libs += ['-lwinmm', '-ldwmapi', '-lsetupapi', '-lcfgmgr32']
   backend_immodules += ['ime']
+
+# Check whether libepoxy is built with EGL support on Windows
+  win32_has_egl = cc.links(
+     '''
+     #include <epoxy/egl.h>
+
+     int main(int argc, char *argv[])
+     {
+       EGLDisplay disp = EGL_NO_DISPLAY;
+
+       return epoxy_egl_version (disp);
+     }
+     ''',
+     dependencies : epoxy_dep,
+     name : 'libepoxy supports EGL on Windows'
+    )
+
 endif
 
 # Check for bind_textdomain_codeset, including -lintl if GLib brings it in by