plugins: record downstream GstGLContext.

Record GL context supplied by downstream elements. This can be useful,
and further needed, to enforce run-time check that the GL context is
compatible for use by libgstvaapi. e.g. check that we don't create a
VA/GLX display for EGL/X11 contexts.

https://bugzilla.gnome.org/show_bug.cgi?id=725643

Original-path-by: Matthew Waters <ystreet00@gmail.com>

configure.ac

@@ -503,6 +503,38 @@ dnl ... video parsers
 AM_CONDITIONAL([USE_LOCAL_VIDEO_PARSERS],
     [test "$enable_builtin_videoparsers" = "yes"])
 
+dnl ... opengl helper libraries
+HAVE_GSTGL=0
+if test "$enable_glx" = "yes" -o "$enable_egl" = "yes"; then
+    PKG_CHECK_MODULES([GST_GL],
+        [gstreamer-gl-$GST_PKG_VERSION >= $GST_PLUGINS_BAD_VERSION_REQUIRED],
+        [HAVE_GSTGL=1], [HAVE_GSTGL=0])
+fi
+
+if test $HAVE_GSTGL -eq 1; then
+    AC_CACHE_CHECK([for GStreamer OpenGL helper libraries],
+        [ac_cv_have_gst_gl_helpers], [
+        saved_CPPFLAGS="$CPPFLAGS"
+        CPPFLAGS="$CPPFLAGS $GST_GL_CFLAGS"
+        saved_LIBS="$LIBS"
+        LIBS="$saved_LIBS"
+        AC_CHECK_HEADERS([gst/gl/gl.h], [:], [HAVE_GSTGL=0])
+        AC_COMPILE_IFELSE(
+            [AC_LANG_PROGRAM(
+                [[#include <gst/gl/gl.h>]],
+                [[GstGLContext gl_context;]])],
+            [ac_cv_have_gst_gl_helpers="yes"],
+            [ac_cv_have_gst_gl_helpers="no" HAVE_GSTGL=0]
+        )
+        CPPFLAGS="$saved_CPPFLAGS"
+        LIBS="$saved_LIBS"
+    ])
+fi
+AM_CONDITIONAL([USE_GST_GL_HELPERS], [test $HAVE_GSTGL -eq 1])
+
+AC_DEFINE_UNQUOTED([USE_GST_GL_HELPERS], [$HAVE_GSTGL],
+    [Defined to 1 if GStreamer OpenGL helper libraries are available])
+
 case $GST_API_VERSION in
 0.10)   lt_bias=gst0_vaapi_lt_current_bias;;
 1.0)    lt_bias=gst1_vaapi_lt_current_bias;;

gst/vaapi/Makefile.am

@@ -35,6 +35,11 @@ libgstvaapi_LIBS += \
 	$(top_builddir)/gst-libs/gst/vaapi/libgstvaapi-wayland-$(GST_API_VERSION).la
 endif
 
+if USE_GST_GL_HELPERS
+libgstvaapi_CFLAGS	+= $(GST_GL_CFLAGS)
+libgstvaapi_LIBS	+= $(GST_GL_LIBS)
+endif
+
 libgstvaapi_source_c = \
 	gstvaapi.c		\
 	gstvaapidecode.c	\

gst/vaapi/gstvaapipluginbase.c

@@ -295,6 +295,7 @@ gst_vaapi_plugin_base_close (GstVaapiPluginBase * plugin)
 {
   g_clear_object (&plugin->uploader);
   gst_vaapi_display_replace (&plugin->display, NULL);
+  gst_object_replace (&plugin->gl_context, NULL);
 
   gst_caps_replace (&plugin->sinkpad_caps, NULL);
   plugin->sinkpad_caps_changed = FALSE;
@@ -629,12 +630,17 @@ gst_vaapi_plugin_base_decide_allocation (GstVaapiPluginBase * plugin,
   gboolean has_video_alignment = FALSE;
 #if GST_CHECK_VERSION(1,1,0) && USE_GLX
   gboolean has_texture_upload_meta = FALSE;
+  guint idx;
 #endif
 
   g_return_val_if_fail (plugin->display != NULL, FALSE);
 
   gst_query_parse_allocation (query, &caps, &need_pool);
 
+  /* We don't need any GL context beyond this point if not requested
+     so explicitly through GstVideoGLTextureUploadMeta */
+  gst_object_replace (&plugin->gl_context, NULL);
+
   if (!caps)
     goto error_no_caps;
 
@@ -648,7 +654,23 @@ gst_vaapi_plugin_base_decide_allocation (GstVaapiPluginBase * plugin,
 
 #if GST_CHECK_VERSION(1,1,0) && USE_GLX
   has_texture_upload_meta = gst_query_find_allocation_meta (query,
-      GST_VIDEO_GL_TEXTURE_UPLOAD_META_API_TYPE, NULL);
+      GST_VIDEO_GL_TEXTURE_UPLOAD_META_API_TYPE, &idx);
+
+#if USE_GST_GL_HELPERS
+  if (has_texture_upload_meta) {
+    const GstStructure *params;
+    GstObject *gl_context;
+
+    gst_query_parse_nth_allocation_meta (query, idx, &params);
+    if (params) {
+      if (gst_structure_get (params, "gst.gl.GstGLContext", GST_GL_TYPE_CONTEXT,
+              &gl_context, NULL) && gl_context) {
+        gst_vaapi_plugin_base_set_gl_context (plugin, gl_context);
+        gst_object_unref (gl_context);
+      }
+    }
+  }
+#endif
 #endif
 
   gst_video_info_init (&vi);
@@ -936,3 +958,22 @@ error_copy_buffer:
     return GST_FLOW_NOT_SUPPORTED;
   }
 }
+
+/**
+ * gst_vaapi_plugin_base_set_gl_context:
+ * @plugin: a #GstVaapiPluginBase
+ * @object: the new GL context from downstream
+ *
+ * Registers the new GL context. The change is effective at the next
+ * call to gst_vaapi_plugin_base_ensure_display(), where the
+ * underlying display object could be re-allocated to fit the GL
+ * context needs
+ */
+void
+gst_vaapi_plugin_base_set_gl_context (GstVaapiPluginBase * plugin,
+    GstObject * object)
+{
+#if USE_GST_GL_HELPERS
+  gst_object_replace (&plugin->gl_context, object);
+#endif
+}

gst/vaapi/gstvaapipluginbase.h

@@ -32,6 +32,10 @@
 #include <gst/vaapi/gstvaapidisplay.h>
 #include "gstvaapiuploader.h"
 
+#ifdef HAVE_GST_GL_GL_H
+# include <gst/gl/gstglcontext.h>
+#endif
+
 G_BEGIN_DECLS
 
 typedef struct _GstVaapiPluginBase GstVaapiPluginBase;
@@ -145,6 +149,8 @@ struct _GstVaapiPluginBase
   GstVaapiDisplayType display_type_req;
   gchar *display_name;
 
+  GstObject *gl_context;
+
   GstVaapiUploader *uploader;
   gboolean uploader_used;
 };
@@ -233,6 +239,11 @@ GstFlowReturn
 gst_vaapi_plugin_base_get_input_buffer (GstVaapiPluginBase * plugin,
     GstBuffer * inbuf, GstBuffer ** outbuf_ptr);
 
+G_GNUC_INTERNAL
+void
+gst_vaapi_plugin_base_set_gl_context (GstVaapiPluginBase * plugin,
+    GstObject * object);
+
 G_END_DECLS
 
 #endif /* GST_VAAPI_PLUGIN_BASE_H */