[vlc-devel] [PATCH 6/7] egl_display: improve support detection

[Romain Vimont]

A module egl_display must only provide EGL displays where eglTerminate()
can be called, even if other modules are using EGL (typically because it
is internally refcounted).

This is always the case on Android, so egl_display was initially only
enabled on Android:
https://android.googlesource.com/platform/frameworks/native/+/master/opengl/libs/EGL/egl_display.cpp

But this may also be the case on other platforms which support
EGL_KHR_display_reference:
https://www.khronos.org/registry/EGL/extensions/KHR/EGL_KHR_display_reference.txt

Co-authored-by: Alexandre Janniaux <ajanni at videolabs.io>
---
 modules/video_output/opengl/Makefile.am       |  2 +-
 .../video_output/opengl/egl_display_generic.c | 36 +++++++++++++++++++
 2 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/modules/video_output/opengl/Makefile.am b/modules/video_output/opengl/Makefile.am
index 3bee347ef0..c7cbdedfb6 100644
--- a/modules/video_output/opengl/Makefile.am
+++ b/modules/video_output/opengl/Makefile.am
@@ -92,7 +92,7 @@ endif # HAVE_GL
 libegl_display_generic_plugin_la_SOURCES = video_output/opengl/egl_display_generic.c
 libegl_display_generic_plugin_la_CPPFLAGS = $(AM_CPPFLAGS) $(EGL_FLAGS)
 libegl_display_generic_plugin_la_LIBADD = $(EGL_LIBS)
-if HAVE_ANDROID
+if HAVE_EGL
 vout_LTLIBRARIES += libegl_display_generic_plugin.la
 endif
 
diff --git a/modules/video_output/opengl/egl_display_generic.c b/modules/video_output/opengl/egl_display_generic.c
index dfa68125c4..cca13beec8 100644
--- a/modules/video_output/opengl/egl_display_generic.c
+++ b/modules/video_output/opengl/egl_display_generic.c
@@ -31,11 +31,47 @@
 
 #include "egl_display.h"
 
+static EGLenum GetPlatform(const char *extensions)
+{
+#ifdef EGL_KHR_platform_x11
+    if (vlc_gl_StrHasToken(extensions, "EGL_EXT_platform_x11"))
+        return EGL_PLATFORM_X11_KHR;
+#endif
+
+#ifdef EGL_KHR_platform_wayland
+    if (vlc_gl_StrHasToken(extensions, "EGL_EXT_platform_wayland"))
+        return EGL_PLATFORM_WAYLAND_KHR;
+#endif
+
+    return 0;
+}
+
 static vlc_egl_display_open_fn Open;
 static int
 Open(struct vlc_egl_display *display)
 {
+#ifdef __ANDROID__
+    /* The default display is refcounted on Android */
     display->display = eglGetDisplay(EGL_DEFAULT_DISPLAY);
+#elif defined(EGL_KHR_display_reference)
+    const char *extensions = eglQueryString(EGL_NO_DISPLAY, EGL_EXTENSIONS);
+
+    if (!vlc_gl_StrHasToken(extensions, "EGL_KHR_display_reference"))
+        return VLC_EGENERIC;
+
+    EGLenum platform = GetPlatform(extensions);
+    if (!platform)
+        return VLC_EGENERIC;
+
+    const EGLAttrib attribs[] = {
+        EGL_TRACK_REFERENCES_KHR, EGL_TRUE,
+        EGL_NONE,
+    };
+
+    display->display =
+        eglGetPlatformDisplay(platform, EGL_DEFAULT_DISPLAY, attribs);
+#endif
+
     if (display->display == EGL_NO_DISPLAY)
         return VLC_EGENERIC;
 
-- 
2.30.1