buffer: track asynchronous buffers and don't release them until unref

synchronous buffers are read instantly and we can release them, but asynchronous ones have to be locked until they are unref'd from .current to avoid reading from a buffer after .release()

1 files changed, 12 insertions, 4 deletions

diff --git a/src/protocols/core/Compositor.cpp b/src/protocols/core/Compositor.cpp
index e8503ae8..db6e3258 100644
--- a/src/protocols/core/Compositor.cpp
+++ b/src/protocols/core/Compositor.cpp
@@ -107,6 +107,7 @@ CWLSurfaceResource::CWLSurfaceResource(SP<CWlSurface> resource_) : resource(reso
 
         pending.damage.intersect(CBox{{}, pending.size});
 
+        auto    previousBuffer       = current.buffer;
         CRegion previousBufferDamage = accumulateCurrentBufferDamage();
 
         current = pending;
@@ -119,11 +120,12 @@ CWLSurfaceResource::CWLSurfaceResource(SP<CWlSurface> resource_) : resource(reso
             //    current.damage.copy().scale(current.scale).transform(current.transform, current.size.x, current.size.y).add(current.bufferDamage).add(previousBufferDamage);
             current.buffer->update(CBox{{}, {INT32_MAX, INT32_MAX}}); // FIXME: figure this out to not use this hack. QT apps are wonky without this.
 
-            // release the buffer, glTexImage2D is synchronous (as in, data is consumed after the call returns)
+            // release the buffer if it's synchronous as update() has done everything thats needed
             // so we can let the app know we're done.
-            // for dma buffers, this doesn't matter.
-            current.buffer->sendRelease();
-            bufferReleased = true;
+            if (current.buffer->isSynchronous()) {
+                current.buffer->sendRelease();
+                bufferReleased = true;
+            }
         }
 
         // TODO: we should _accumulate_ and not replace above if sync
@@ -146,6 +148,12 @@ CWLSurfaceResource::CWLSurfaceResource(SP<CWlSurface> resource_) : resource(reso
                 },
                 nullptr);
         }
+
+        // for async buffers, we can only release the buffer once we are unrefing it from current.
+        if (previousBuffer && !previousBuffer->isSynchronous() && !bufferReleased) {
+            previousBuffer->sendRelease();
+            bufferReleased = true;
+        }
     });
 
     resource->setDamage([this](CWlSurface* r, int32_t x, int32_t y, int32_t w, int32_t h) { pending.damage.add(CBox{x, y, w, h}); });