Do not queue trivial buffer for unsupported screenshot request.

When screenshot is not supported, we queue an empty buffer to the
requesting producer. Besides returning a useless screenshot, this
overwrites the valuable error code, returning ERROR_OK whenever we
successfully return the trivial buffer.

Instead, refuse to queue the trivial buffer, and return the original
error code.

This replaces the workaround proposed in
I6da5d2fdecdef6c87d4dd7b353e2464678800110

BUG:27505438
Change-Id: I597a9be25071d2a6ddafb7d39cc1b09fb48d5fd0

2 files changed, 12 insertions, 4 deletions

diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index db03c23b36..3a0e21fb76 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -3440,14 +3440,18 @@ status_t SurfaceFlinger::captureScreenImplLocked(
                     } else {
                         ALOGE("got GL_FRAMEBUFFER_COMPLETE_OES error while taking screenshot");
                         result = INVALID_OPERATION;
+                        window->cancelBuffer(window, buffer, syncFd);
+                        buffer = NULL;
                     }
                     // destroy our image
                     eglDestroyImageKHR(mEGLDisplay, image);
                 } else {
                     result = BAD_VALUE;
                 }
-                // queueBuffer takes ownership of syncFd
-                result = window->queueBuffer(window, buffer, syncFd);
+                if (buffer) {
+                    // queueBuffer takes ownership of syncFd
+                    result = window->queueBuffer(window, buffer, syncFd);
+                }
             }
         } else {
             result = BAD_VALUE;
diff --git a/services/surfaceflinger/SurfaceFlinger_hwc1.cpp b/services/surfaceflinger/SurfaceFlinger_hwc1.cpp
index 16332f34cd..d864874a55 100644
--- a/services/surfaceflinger/SurfaceFlinger_hwc1.cpp
+++ b/services/surfaceflinger/SurfaceFlinger_hwc1.cpp
@@ -3478,14 +3478,18 @@ status_t SurfaceFlinger::captureScreenImplLocked(
                     } else {
                         ALOGE("got GL_FRAMEBUFFER_COMPLETE_OES error while taking screenshot");
                         result = INVALID_OPERATION;
+                        window->cancelBuffer(window, buffer, syncFd);
+                        buffer = NULL;
                     }
                     // destroy our image
                     eglDestroyImageKHR(mEGLDisplay, image);
                 } else {
                     result = BAD_VALUE;
                 }
-                // queueBuffer takes ownership of syncFd
-                result = window->queueBuffer(window, buffer, syncFd);
+                if (buffer) {
+                    // queueBuffer takes ownership of syncFd
+                    result = window->queueBuffer(window, buffer, syncFd);
+                }
             }
         } else {
             result = BAD_VALUE;