[vlc-devel] [PATCH 1/2] egl_pbuffer: improve support detection

[Romain Vimont]

The video filter egl_pbuffer may be used only if the display is
refcounted, because we don't know if other modules are using EGL.

This is always the case on Android, so egl_pbuffer 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_filter/egl_pbuffer.c      | 53 ++++++++++++++++++++++++-
 modules/video_output/opengl/Makefile.am |  7 ++++
 2 files changed, 58 insertions(+), 2 deletions(-)

diff --git a/modules/video_filter/egl_pbuffer.c b/modules/video_filter/egl_pbuffer.c
index 0ecc2562d0..78cd48b3fd 100644
--- a/modules/video_filter/egl_pbuffer.c
+++ b/modules/video_filter/egl_pbuffer.c
@@ -127,12 +127,61 @@ static bool DestroyImageKHR(vlc_gl_t *gl, void *image)
     return sys->eglDestroyImageKHR(sys->display, image);
 }
 
-static int InitEGL(vlc_gl_t *gl, unsigned width, unsigned height)
+static bool GetPlatform(const char *extensions, EGLenum *out)
+{
+#ifdef EGL_KHR_platform_x11
+    if (vlc_gl_StrHasToken(extensions, "EGL_EXT_platform_x11"))
+    {
+        *out = EGL_PLATFORM_X11_KHR;
+        return true;
+    }
+#endif
+
+#ifdef EGL_KHR_platform_wayland
+    if (vlc_gl_StrHasToken(extensions, "EGL_EXT_platform_wayland"))
+    {
+        *out = EGL_PLATFORM_WAYLAND_KHR;
+        return true;
+    }
+#endif
+
+    return false;
+}
+
+static bool InitDefaultEGLDisplay(vlc_gl_t *gl)
 {
     struct vlc_gl_pbuffer *sys = gl->sys;
 
+#ifdef __ANDROID__
+    /* The default display is refcounted on Android */
     sys->display = eglGetDisplay(EGL_DEFAULT_DISPLAY);
-    if (sys->display == EGL_NO_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 false;
+
+    EGLenum platform;
+    if (!GetPlatform(extensions, &platform))
+        return false;
+
+    const EGLAttrib attribs[] = {
+        EGL_TRACK_REFERENCES_KHR, EGL_TRUE,
+        EGL_NONE,
+    };
+
+    sys->display =
+        eglGetPlatformDisplay(platform, EGL_DEFAULT_DISPLAY, attribs);
+#endif
+
+    return sys->display != EGL_NO_DISPLAY;
+}
+
+static int InitEGL(vlc_gl_t *gl, unsigned width, unsigned height)
+{
+    struct vlc_gl_pbuffer *sys = gl->sys;
+
+    if (!InitDefaultEGLDisplay(gl))
         return VLC_EGENERIC;
 
     /* Initialize EGL display */
diff --git a/modules/video_output/opengl/Makefile.am b/modules/video_output/opengl/Makefile.am
index dcb8ace5c6..d3170d9ac7 100644
--- a/modules/video_output/opengl/Makefile.am
+++ b/modules/video_output/opengl/Makefile.am
@@ -93,6 +93,13 @@ libegl_pbuffer_filter_plugin_la_SOURCES = video_filter/egl_pbuffer.c
 libegl_pbuffer_filter_plugin_la_CPPFLAGS = $(AM_CPPFLAGS) $(EGL_FLAGS)
 libegl_pbuffer_filter_plugin_la_LIBADD = $(LIBM) $(EGL_LIBS)
 
+if HAVE_LINUX
+if HAVE_GL
+libegl_pbuffer_filter_plugin_la_LIBADD += libvlc_opengl.la $(GL_LIBS)
+vout_LTLIBRARIES += libegl_pbuffer_filter_plugin.la
+endif
+endif
+
 if HAVE_ANDROID
 libegl_pbuffer_filter_plugin_la_LIBADD += libvlc_opengles.la $(GLES2_LIBS)
 libegl_pbuffer_filter_plugin_la_CPPFLAGS += -DUSE_OPENGL_ES2=1
-- 
2.30.1