Expand on the SurfaceTexture API docs.

This change adds additional documentation explaining how a
SurfaceTexture should be used in OpenGL ES.  It describes some of the
limitations of using the GL_TEXTURE_EXTERNAL_OES texture target.

Change-Id: I7424c1b422e4f402e87372e8b361391fbec82c5c

1 files changed, 7 insertions, 1 deletions

diff --git a/graphics/java/android/graphics/SurfaceTexture.java b/graphics/java/android/graphics/SurfaceTexture.java
index 2d23fe9..970b207 100644
--- a/graphics/java/android/graphics/SurfaceTexture.java
+++ b/graphics/java/android/graphics/SurfaceTexture.java
@@ -45,7 +45,13 @@ import android.os.Message;
  * be done by transforming (1, 1, 0, 1).
  *
  * <p>The texture object uses the GL_TEXTURE_EXTERNAL_OES texture target, which is defined by the
- * OES_EGL_image_external OpenGL ES extension.  This limits how the texture may be used.
+ * <a href="http://www.khronos.org/registry/gles/extensions/OES/OES_EGL_image_external.txt">
+ * GL_OES_EGL_image_external</a> OpenGL ES extension.  This limits how the texture may be used.
+ * Each time the texture is bound it must be bound to the GL_TEXTURE_EXTERNAL_OES target rather than
+ * the GL_TEXTURE_2D target.  Additionally, any OpenGL ES 2.0 shader that samples from the texture
+ * must declare its use of this extension using, for example, an "#extension
+ * GL_OES_EGL_image_external : require" directive.  Such shaders must also access the texture using
+ * the samplerExternalOES GLSL sampler type.
  *
  * <p>SurfaceTexture objects may be created on any thread.  {@link #updateTexImage} may only be
  * called on the thread with the OpenGL ES context that contains the texture object.  The