sometimes we would incorrectly scale the content of a surface

this would happen when a resize was pending (ie: we have received
and processed a resize transaction but have not received a buffer
with the right size) and a new transaction came in that didn't
involve a resize, for instance a translate-only transaction.

in this case, we would incorrectly update the drawing state
with the pending size, eventhough we still don't have a buffer
for it.

the solution is quite simple, we never allow the size to propagate
from current to drawing state during the regular transaction processing
(unless we are in fixed-size mode -- meaning we don't need to have
a matching size buffer), this propagation happens later once we
receive the buffer.

Bug: 6624163
Change-Id: I11a97e4b88a7f3a0571ddcfe99c86cb04ce01a4d

1 files changed, 19 insertions, 6 deletions

diff --git a/services/surfaceflinger/Layer.cpp b/services/surfaceflinger/Layer.cpp
index 593f1781ae..40623404d4 100644
--- a/services/surfaceflinger/Layer.cpp
+++ b/services/surfaceflinger/Layer.cpp
@@ -469,18 +469,31 @@ uint32_t Layer::doTransaction(uint32_t flags)
                 front.requested.crop.getWidth(),
                 front.requested.crop.getHeight());
 
-        if (!isFixedSize()) {
-            // this will make sure LayerBase::doTransaction doesn't update
-            // the drawing state's geometry
-            flags |= eDontUpdateGeometryState;
-        }
-
         // record the new size, form this point on, when the client request
         // a buffer, it'll get the new size.
         mSurfaceTexture->setDefaultBufferSize(
                 temp.requested.w, temp.requested.h);
     }
 
+    if (!isFixedSize()) {
+
+        const bool resizePending = (temp.requested.w != temp.active.w) ||
+                                   (temp.requested.h != temp.active.h);
+
+        if (resizePending) {
+            // don't let LayerBase::doTransaction update the drawing state
+            // if we have a pending resize, unless we are in fixed-size mode.
+            // the drawing state will be updated only once we receive a buffer
+            // with the correct size.
+            //
+            // in particular, we want to make sure the clip (which is part
+            // of the geometry state) is latched together with the size but is
+            // latched immediately when no resizing is involved.
+
+            flags |= eDontUpdateGeometryState;
+        }
+    }
+
     return LayerBase::doTransaction(flags);
 }