diff --git a/include/gui/SurfaceTextureClient.h b/include/gui/SurfaceTextureClient.h
index 4cdece9..7992105 100644
--- a/include/gui/SurfaceTextureClient.h
+++ b/include/gui/SurfaceTextureClient.h
@@ -33,6 +33,8 @@
 public:
     SurfaceTextureClient(const sp<ISurfaceTexture>& surfaceTexture);
 
+    sp<ISurfaceTexture> getISurfaceTexture() const;
+
 private:
 
     // can't be copied
diff --git a/include/ui/egl/android_natives.h b/include/ui/egl/android_natives.h
index 0ac34d0..0fc1ddf 100644
--- a/include/ui/egl/android_natives.h
+++ b/include/ui/egl/android_natives.h
@@ -110,6 +110,14 @@
      * conjunction with this query.
      */
     NATIVE_WINDOW_QUEUES_TO_WINDOW_COMPOSER,
+
+    /* Get the concrete type of a ANativeWindow.  See below for the list of
+     * possible return values.
+     *
+     * This query should not be used outside the Android framework and will
+     * likely be removed in the near future.
+     */
+    NATIVE_WINDOW_CONCRETE_TYPE,
 };
 
 /* valid operations for the (*perform)() hook */
@@ -142,6 +150,13 @@
     NATIVE_WINDOW_TRANSFORM_ROT_270 = HAL_TRANSFORM_ROT_270,
 };
 
+/* values returned by the NATIVE_WINDOW_CONCRETE_TYPE query */
+enum {
+    NATIVE_WINDOW_FRAMEBUFFER,                  // FramebufferNativeWindow
+    NATIVE_WINDOW_SURFACE,                      // Surface
+    NATIVE_WINDOW_SURFACE_TEXTURE_CLIENT,       // SurfaceTextureClient
+};
+
 struct ANativeWindow 
 {
 #ifdef __cplusplus
diff --git a/include/utils/String8.h b/include/utils/String8.h
index 6b49ff5..4163697 100644
--- a/include/utils/String8.h
+++ b/include/utils/String8.h
@@ -165,8 +165,8 @@
     String8 walkPath(String8* outRemains = NULL) const;
 
     /*
-     * Return the filename extension.  This is the last '.' and up to
-     * four characters that follow it.  The '.' is included in case we
+     * Return the filename extension.  This is the last '.' and any number
+     * of characters that follow it.  The '.' is included in case we
      * decide to expand our definition of what constitutes an extension.
      *
      * "/tmp/foo/bar.c" --> ".c"
diff --git a/libs/gui/SurfaceTextureClient.cpp b/libs/gui/SurfaceTextureClient.cpp
index a40fac9..7f1d9cb 100644
--- a/libs/gui/SurfaceTextureClient.cpp
+++ b/libs/gui/SurfaceTextureClient.cpp
@@ -40,6 +40,10 @@
     mAllocator = mSurfaceTexture->getAllocator();
 }
 
+sp<ISurfaceTexture> SurfaceTextureClient::getISurfaceTexture() const {
+    return mSurfaceTexture;
+}
+
 int SurfaceTextureClient::setSwapInterval(ANativeWindow* window, int interval) {
     SurfaceTextureClient* c = getSelf(window);
     return c->setSwapInterval(interval);
@@ -160,6 +164,9 @@
         // SurfaceTextureClient currently never queues frames to SurfaceFlinger.
         *value = 0;
         return NO_ERROR;
+    case NATIVE_WINDOW_CONCRETE_TYPE:
+        *value = NATIVE_WINDOW_SURFACE_TEXTURE_CLIENT;
+        return NO_ERROR;
     }
     return BAD_VALUE;
 }
diff --git a/libs/gui/tests/SurfaceTextureClient_test.cpp b/libs/gui/tests/SurfaceTextureClient_test.cpp
index 0f140ff..94b05bc 100644
--- a/libs/gui/tests/SurfaceTextureClient_test.cpp
+++ b/libs/gui/tests/SurfaceTextureClient_test.cpp
@@ -14,8 +14,9 @@
  * limitations under the License.
  */
 
-#include <gui/SurfaceTextureClient.h>
+#include <EGL/egl.h>
 #include <gtest/gtest.h>
+#include <gui/SurfaceTextureClient.h>
 
 namespace android {
 
@@ -35,6 +36,11 @@
     sp<SurfaceTextureClient> mSTC;
 };
 
+TEST_F(SurfaceTextureClientTest, GetISurfaceTextureIsNotNull) {
+    sp<ISurfaceTexture> ist(mSTC->getISurfaceTexture());
+    ASSERT_TRUE(ist != NULL);
+}
+
 TEST_F(SurfaceTextureClientTest, QueuesToWindowCompositorIsFalse) {
     sp<ANativeWindow> anw(mSTC);
     int result = -123;
@@ -44,4 +50,54 @@
     EXPECT_EQ(0, result);
 }
 
+TEST_F(SurfaceTextureClientTest, ConcreteTypeIsSurfaceTextureClient) {
+    sp<ANativeWindow> anw(mSTC);
+    int result = -123;
+    int err = anw->query(anw.get(), NATIVE_WINDOW_CONCRETE_TYPE, &result);
+    EXPECT_EQ(NO_ERROR, err);
+    EXPECT_EQ(NATIVE_WINDOW_SURFACE_TEXTURE_CLIENT, result);
+}
+
+TEST_F(SurfaceTextureClientTest, ANativeWindowLockFails) {
+    sp<ANativeWindow> anw(mSTC);
+    ANativeWindow_Buffer buf;
+    ASSERT_EQ(BAD_VALUE, ANativeWindow_lock(anw.get(), &buf, NULL));
+}
+
+TEST_F(SurfaceTextureClientTest, EglCreateWindowSurfaceFails) {
+    sp<ANativeWindow> anw(mSTC);
+
+    EGLDisplay dpy = eglGetDisplay(EGL_DEFAULT_DISPLAY);
+    ASSERT_EQ(EGL_SUCCESS, eglGetError());
+    ASSERT_NE(EGL_NO_DISPLAY, dpy);
+
+    EGLint majorVersion;
+    EGLint minorVersion;
+    EXPECT_TRUE(eglInitialize(dpy, &majorVersion, &minorVersion));
+    ASSERT_EQ(EGL_SUCCESS, eglGetError());
+
+    EGLConfig myConfig = {0};
+    EGLint numConfigs = 0;
+    EGLint configAttribs[] = {
+        EGL_SURFACE_TYPE, EGL_WINDOW_BIT,
+        EGL_RENDERABLE_TYPE, EGL_OPENGL_ES2_BIT,
+        EGL_RED_SIZE, 8,
+        EGL_GREEN_SIZE, 8,
+        EGL_BLUE_SIZE, 8,
+        EGL_ALPHA_SIZE, 8,
+        EGL_DEPTH_SIZE, 16,
+        EGL_STENCIL_SIZE, 8,
+        EGL_NONE };
+    EXPECT_TRUE(eglChooseConfig(dpy, configAttribs, &myConfig, 1,
+            &numConfigs));
+    ASSERT_EQ(EGL_SUCCESS, eglGetError());
+
+    EGLSurface eglSurface = eglCreateWindowSurface(dpy, myConfig, anw.get(),
+            NULL);
+    ASSERT_EQ(EGL_NO_SURFACE, eglSurface);
+    ASSERT_EQ(EGL_BAD_NATIVE_WINDOW, eglGetError());
+
+    eglTerminate(dpy);
+}
+
 }
diff --git a/libs/surfaceflinger_client/Surface.cpp b/libs/surfaceflinger_client/Surface.cpp
index afabbf4..21d509a 100644
--- a/libs/surfaceflinger_client/Surface.cpp
+++ b/libs/surfaceflinger_client/Surface.cpp
@@ -712,11 +712,15 @@
     case NATIVE_WINDOW_MIN_UNDEQUEUED_BUFFERS:
         *value = MIN_UNDEQUEUED_BUFFERS;
         return NO_ERROR;
-    case NATIVE_WINDOW_QUEUES_TO_WINDOW_COMPOSER:
+    case NATIVE_WINDOW_QUEUES_TO_WINDOW_COMPOSER: {
         sp<ISurfaceComposer> sf(ComposerService::getComposerService());
         *value = sf->authenticateSurface(mSurface) ? 1 : 0;
         return NO_ERROR;
     }
+    case NATIVE_WINDOW_CONCRETE_TYPE:
+        *value = NATIVE_WINDOW_SURFACE;
+        return NO_ERROR;
+    }
     return BAD_VALUE;
 }
 
diff --git a/libs/surfaceflinger_client/tests/Surface_test.cpp b/libs/surfaceflinger_client/tests/Surface_test.cpp
index 74ebf4e..fd07479 100644
--- a/libs/surfaceflinger_client/tests/Surface_test.cpp
+++ b/libs/surfaceflinger_client/tests/Surface_test.cpp
@@ -130,4 +130,12 @@
     ASSERT_TRUE(heap != NULL);
 }
 
+TEST_F(SurfaceTest, ConcreteTypeIsSurface) {
+    sp<ANativeWindow> anw(mSurface);
+    int result = -123;
+    int err = anw->query(anw.get(), NATIVE_WINDOW_CONCRETE_TYPE, &result);
+    EXPECT_EQ(NO_ERROR, err);
+    EXPECT_EQ(NATIVE_WINDOW_SURFACE, result);
+}
+
 }
diff --git a/libs/ui/FramebufferNativeWindow.cpp b/libs/ui/FramebufferNativeWindow.cpp
index 0702d49..dc223f9 100644
--- a/libs/ui/FramebufferNativeWindow.cpp
+++ b/libs/ui/FramebufferNativeWindow.cpp
@@ -286,6 +286,9 @@
         case NATIVE_WINDOW_FORMAT:
             *value = fb->format;
             return NO_ERROR;
+        case NATIVE_WINDOW_CONCRETE_TYPE:
+            *value = NATIVE_WINDOW_FRAMEBUFFER;
+            return NO_ERROR;
     }
     *value = 0;
     return BAD_VALUE;
diff --git a/opengl/libs/EGL/egl.cpp b/opengl/libs/EGL/egl.cpp
index 3d5a4d1..f4a1650 100644
--- a/opengl/libs/EGL/egl.cpp
+++ b/opengl/libs/EGL/egl.cpp
@@ -1094,6 +1094,16 @@
         EGLConfig iConfig = dp->configs[intptr_t(config)].config;
         EGLint format;
 
+        // for now fail if the window is not a Surface.
+        int type = -1;
+        ANativeWindow* anw = reinterpret_cast<ANativeWindow*>(window);
+        if ((anw->query(window, NATIVE_WINDOW_CONCRETE_TYPE, &type) != 0) ||
+                (type == NATIVE_WINDOW_SURFACE_TEXTURE_CLIENT)) {
+            LOGE("native window is a SurfaceTextureClient (currently "
+                    "unsupported)");
+            return setError(EGL_BAD_NATIVE_WINDOW, EGL_NO_SURFACE);
+        }
+
         // set the native window's buffers format to match this config
         if (cnx->egl.eglGetConfigAttrib(iDpy,
                 iConfig, EGL_NATIVE_VISUAL_ID, &format)) {