RHIBuffer: don't destroy buffer immediately when orphaning

We need to keep past QRhiBuffer alive long enough to have submitted any
updates we might have already recorded for them.

Change-Id: I3807cbca64773b0c61afefd6378ae397b175c2e5
Reviewed-by: Mike Krus <mike.krus@kdab.com>

3 files changed, 26 insertions, 2 deletions

diff --git a/src/plugins/renderers/rhi/io/rhibuffer.cpp b/src/plugins/renderers/rhi/io/rhibuffer.cpp
index edff21e0c..0f19bf250 100644
--- a/src/plugins/renderers/rhi/io/rhibuffer.cpp
+++ b/src/plugins/renderers/rhi/io/rhibuffer.cpp
@@ -116,17 +116,32 @@ bool RHIBuffer::bind(SubmissionContext *ctx, Type t)
 void RHIBuffer::destroy()
 {
     if (m_rhiBuffer) {
-        m_rhiBuffer->destroy();
         delete m_rhiBuffer;
         m_rhiBuffer = nullptr;
     }
+    destroyOrphaned();
     m_allocSize = 0;
 }
 
+void RHIBuffer::destroyOrphaned()
+{
+    for (QRhiBuffer *oldBuffer : m_buffersToCleanup)
+        delete oldBuffer;
+    m_buffersToCleanup.clear();
+}
+
+// Note: when we orphan, we have to keep the previous QRhiBuffer alive until
+// after frame has been submitted. This is because we might have already stored
+// updates in the RHI Command Buffers for the buffer that is about to be
+// destroyed. We therefore have to wait until command buffer has been submitted
+// until we can destroy the buffer.
 void RHIBuffer::orphan()
 {
     m_datasToUpload.clear();
-    destroy();
+    if (m_rhiBuffer) {
+        m_buffersToCleanup.push_back(m_rhiBuffer);
+        m_rhiBuffer = nullptr;
+    }
 }
 
 void RHIBuffer::allocate(const QByteArray &data, bool dynamic)
diff --git a/src/plugins/renderers/rhi/io/rhibuffer_p.h b/src/plugins/renderers/rhi/io/rhibuffer_p.h
index 27d26c9a4..4d13836b7 100644
--- a/src/plugins/renderers/rhi/io/rhibuffer_p.h
+++ b/src/plugins/renderers/rhi/io/rhibuffer_p.h
@@ -81,6 +81,7 @@ public:
 
     bool bind(SubmissionContext *ctx, Type t);
     void destroy();
+    void destroyOrphaned();
     void allocate(const QByteArray &data, bool dynamic = true);
     void update(const QByteArray &data, int offset = 0);
     QByteArray download(SubmissionContext *ctx, uint size);
@@ -98,6 +99,8 @@ private:
 
     QRhiBuffer *m_rhiBuffer {};
 
+    std::vector<QRhiBuffer *> m_buffersToCleanup;
+
     std::vector<std::pair<QByteArray /*data*/, int /*offset*/>> m_datasToUpload;
 };
 
diff --git a/src/plugins/renderers/rhi/renderer/renderer.cpp b/src/plugins/renderers/rhi/renderer/renderer.cpp
index 2b9c858d0..096994da1 100644
--- a/src/plugins/renderers/rhi/renderer/renderer.cpp
+++ b/src/plugins/renderers/rhi/renderer/renderer.cpp
@@ -2561,6 +2561,12 @@ void Renderer::cleanGraphicsResources()
     for (Qt3DCore::QNodeId bufferId : buffersToRelease)
         m_submissionContext->releaseBuffer(bufferId);
 
+    const RHIBufferManager *bufferManager = m_RHIResourceManagers->rhiBufferManager();
+    const std::vector<HRHIBuffer> &activeBufferHandles = bufferManager->activeHandles();
+    // Release internal QRhiBuffer that might have been orphaned
+    for (const HRHIBuffer &bufferH : activeBufferHandles)
+        bufferH->destroyOrphaned();
+
     // When Textures are cleaned up, their id is saved so that they can be
     // cleaned up in the render thread
     const QList<Qt3DCore::QNodeId> cleanedUpTextureIds = std::move(m_textureIdsToCleanup);