+Emitting annotations to the trace
+---------------------------------
+
+From whitin OpenGL applications you can embed annotations in the trace file
+through the following extensions:
+
+* [`GL_KHR_debug`](http://www.opengl.org/registry/specs/KHR/debug.txt)
+
+* [`GL_ARB_debug_output`](http://www.opengl.org/registry/specs/ARB/debug_output.txt)
+
+* [`GL_AMD_debug_output`](http://www.opengl.org/registry/specs/AMD/debug_output.txt)
+
+* [`GL_GREMEDY_string_marker`](http://www.opengl.org/registry/specs/GREMEDY/string_marker.txt)
+
+* [`GL_GREMEDY_frame_terminator`](http://www.opengl.org/registry/specs/GREMEDY/frame_terminator.txt)
+
+**apitrace** will advertise and intercept these GL extensions regardless the GL
+implementation supports them or not. So all you have to do is to use these
+extensions when available, and you can be sure they will be available when
+tracing inside **apitrace**.
+
+For example, if you use [GLEW](http://glew.sourceforge.net/) to dynamically
+detect and use GL extensions, you could easily accomplish this by doing:
+
+ void foo() {
+
+ if (GLEW_GREMEDY_string_marker) {
+ glStringMarkerGREMEDY(0, __FUNCTION__ ": enter");
+ }
+
+ ...
+
+ if (GLEW_GREMEDY_string_marker) {
+ glStringMarkerGREMEDY(0, __FUNCTION__ ": leave");
+ }
+
+ }
+
+This has the added advantage of working equally well with gDEBugger.
+
+Also, provided that the OpenGL implementation supports `GL_KHR_debug`, labels
+defined via glObjectLabel() , and the labels of several objects (textures,
+framebuffers, samplers, etc. ) will appear in the GUI state dumps, in the
+parameters tab.
+
+
+For OpenGL ES applications you can embed annotations in the trace file through the
+[`GL_EXT_debug_marker`](http://www.khronos.org/registry/gles/extensions/EXT/EXT_debug_marker.txt)
+extension.
+
+
+For Direct3D applications you can follow the standard procedure for
+[adding user defined events to Visual Studio Graphics Debugger / PIX](http://msdn.microsoft.com/en-us/library/vstudio/hh873200.aspx):
+
+- `D3DPERF_BeginEvent`, `D3DPERF_EndEvent`, and `D3DPERF_SetMarker` for D3D9 applications.
+
+- `ID3DUserDefinedAnnotation::BeginEvent`,
+ `ID3DUserDefinedAnnotation::EndEvent`, and
+ `ID3DUserDefinedAnnotation::SetMarker` for D3D11.1 applications.