drop, not release, prev buffer if 2nd buffer wl_surface.attach is sent

"A wl_buffer that has been attached and then replaced by another attach instead of committed will not receive a release event, and is not used by the compositor." - wl_surface::attach

Author: ikalco

src/protocols/core/Compositor.cpp

@@ -76,6 +76,9 @@ CWLSurfaceResource::CWLSurfaceResource(SP<CWlSurface> resource_) : resource(reso
 
         pending.offset = {x, y};
 
+        if (pending.buffer)
+            pending.buffer.drop();
+
         auto buf = buffer ? CWLBufferResource::fromResource(buffer) : nullptr;
 
         if (buf && buf->buffer) {

src/protocols/types/Buffer.cpp

@@ -88,3 +88,13 @@ SP<IHLBuffer> CHLBufferReference::operator->() const {
 CHLBufferReference::operator bool() const {
     return buffer;
 }
+
+void CHLBufferReference::drop() {
+    if (!buffer)
+        return;
+
+    buffer->nLocks--;
+    ASSERT(buffer->nLocks >= 0);
+
+    buffer = nullptr;
+}

src/protocols/types/Buffer.hpp

@@ -8,6 +8,7 @@
 #include <aquamarine/buffer/Buffer.hpp>
 
 class CSyncReleaser;
+class CHLBufferReference;
 
 class IHLBuffer : public Aquamarine::IBuffer {
   public:
@@ -36,6 +37,8 @@ class IHLBuffer : public Aquamarine::IBuffer {
 
   private:
     int nLocks = 0;
+
+    friend class CHLBufferReference;
 };
 
 // for ref-counting. Releases in ~dtor
@@ -53,6 +56,9 @@ class CHLBufferReference {
     SP<IHLBuffer>       operator->() const;
     operator bool() const;
 
+    // unlock and drop the buffer without sending release
+    void               drop();
+
     CDRMSyncPointState release;
     SP<IHLBuffer>      buffer;
 };