DirectShow: Postpone setting camera image processing param if not ready

Setting camera image processing parameters fails if the graph
builder is not ready.

We avoid this race condition by having a list of pending parameter
changes which is applied when graph builder has been created.

Task-number: QTBUG-69143
Change-Id: I5702ea5a2dceacff333fcf8dce05372a0208b8d9
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>
Reviewed-by: Maurice Kalinowski <maurice.kalinowski@qt.io>

2 files changed, 12 insertions, 3 deletions

diff --git a/src/plugins/directshow/camera/dscamerasession.cpp b/src/plugins/directshow/camera/dscamerasession.cpp
index ca3c47cb8..324ab44e2 100644
--- a/src/plugins/directshow/camera/dscamerasession.cpp
+++ b/src/plugins/directshow/camera/dscamerasession.cpp
@@ -208,8 +208,8 @@ QVariant DSCameraSession::imageProcessingParameter(
         QCameraImageProcessingControl::ProcessingParameter parameter) const
 {
     if (!m_graphBuilder) {
-        qWarning() << "failed to access to the graph builder";
-        return QVariant();
+        auto it = m_pendingImageProcessingParametrs.find(parameter);
+        return it != m_pendingImageProcessingParametrs.end() ? it.value() : QVariant();
     }
 
     const QCameraImageProcessingControl::ProcessingParameter resultingParameter =
@@ -249,7 +249,7 @@ void DSCameraSession::setImageProcessingParameter(
         const QVariant &value)
 {
     if (!m_graphBuilder) {
-        qWarning() << "failed to access to the graph builder";
+        m_pendingImageProcessingParametrs.insert(parameter, value);
         return;
     }
 
@@ -960,6 +960,13 @@ void DSCameraSession::updateImageProcessingParametersInfos()
     }
 
     pVideoProcAmp->Release();
+
+    for (auto it = m_pendingImageProcessingParametrs.cbegin();
+        it != m_pendingImageProcessingParametrs.cend();
+        ++it) {
+        setImageProcessingParameter(it.key(), it.value());
+    }
+    m_pendingImageProcessingParametrs.clear();
 }
 
 bool DSCameraSession::connectGraph()
diff --git a/src/plugins/directshow/camera/dscamerasession.h b/src/plugins/directshow/camera/dscamerasession.h
index 07c3d9ef9..c3be6144e 100644
--- a/src/plugins/directshow/camera/dscamerasession.h
+++ b/src/plugins/directshow/camera/dscamerasession.h
@@ -230,6 +230,8 @@ private:
     // Internal state
     QCamera::Status m_status;
 
+    QMap<QCameraImageProcessingControl::ProcessingParameter, QVariant> m_pendingImageProcessingParametrs;
+
     friend class SampleGrabberCallbackPrivate;
 };