SurfaceTexture: parameterize the texture target

This change adds a hack to allow Android Browser to use a SurfaceTexture
to stream RGBA images to a GL_TEXTURE_2D texture object.

Change-Id: Idb90064d5d4b920959ef3be7451362ac5012460e

include/gui/SurfaceTexture.h

@@ -20,6 +20,7 @@
 #include <EGL/egl.h>
 #include <EGL/eglext.h>
 #include <GLES2/gl2.h>
+#include <GLES2/gl2ext.h>
 
 #include <gui/ISurfaceTexture.h>
 
@@ -61,7 +62,8 @@ public:
 
     // tex indicates the name OpenGL texture to which images are to be streamed.
     // This texture name cannot be changed once the SurfaceTexture is created.
-    SurfaceTexture(GLuint tex, bool allowSynchronousMode = true);
+    SurfaceTexture(GLuint tex, bool allowSynchronousMode = true,
+            GLenum texTarget = GL_TEXTURE_EXTERNAL_OES);
 
     virtual ~SurfaceTexture();
 
@@ -458,6 +460,14 @@ private:
     // member variables are accessed.
     mutable Mutex mMutex;
 
+    // mTexTarget is the GL texture target with which the GL texture object is
+    // associated.  It is set in the constructor and never changed.  It is
+    // almost always GL_TEXTURE_EXTERNAL_OES except for one use case in Android
+    // Browser.  In that case it is set to GL_TEXTURE_2D to allow
+    // glCopyTexSubImage to read from the texture.  This is a hack to work
+    // around a GL driver limitation on the number of FBO attachments, which the
+    // browser's tile cache exceeds.
+    const GLenum mTexTarget;
 };
 
 // ----------------------------------------------------------------------------

libs/gui/SurfaceTexture.cpp

@@ -94,7 +94,8 @@ static int32_t createProcessUniqueId() {
     return android_atomic_inc(&globalCounter);
 }
 
-SurfaceTexture::SurfaceTexture(GLuint tex, bool allowSynchronousMode) :
+SurfaceTexture::SurfaceTexture(GLuint tex, bool allowSynchronousMode,
+        GLenum texTarget) :
     mDefaultWidth(1),
     mDefaultHeight(1),
     mPixelFormat(PIXEL_FORMAT_RGBA_8888),
@@ -110,7 +111,8 @@ SurfaceTexture::SurfaceTexture(GLuint tex, bool allowSynchronousMode) :
     mSynchronousMode(false),
     mAllowSynchronousMode(allowSynchronousMode),
     mConnectedApi(NO_CONNECTED_API),
-    mAbandoned(false) {
+    mAbandoned(false),
+    mTexTarget(texTarget) {
     // Choose a name using the PID and a process-unique ID.
     mName = String8::format("unnamed-%d-%d", getpid(), createProcessUniqueId());
 
@@ -698,9 +700,8 @@ status_t SurfaceTexture::updateTexImage() {
             ST_LOGW("updateTexImage: clearing GL error: %#04x", error);
         }
 
-        glBindTexture(GL_TEXTURE_EXTERNAL_OES, mTexName);
-        glEGLImageTargetTexture2DOES(GL_TEXTURE_EXTERNAL_OES,
-                (GLeglImageOES)image);
+        glBindTexture(mTexTarget, mTexName);
+        glEGLImageTargetTexture2DOES(mTexTarget, (GLeglImageOES)image);
 
         bool failed = false;
         while ((error = glGetError()) != GL_NO_ERROR) {
@@ -735,7 +736,7 @@ status_t SurfaceTexture::updateTexImage() {
         mDequeueCondition.signal();
     } else {
         // We always bind the texture even if we don't update its contents.
-        glBindTexture(GL_TEXTURE_EXTERNAL_OES, mTexName);
+        glBindTexture(mTexTarget, mTexName);
     }
 
     return OK;
@@ -761,7 +762,7 @@ bool SurfaceTexture::isExternalFormat(uint32_t format)
 }
 
 GLenum SurfaceTexture::getCurrentTextureTarget() const {
-    return GL_TEXTURE_EXTERNAL_OES;
+    return mTexTarget;
 }
 
 void SurfaceTexture::getTransformMatrix(float mtx[16]) {