plugins/screencast: Corrupt header to indicate that buffer has no data

SPA_META_HEADER_FLAG_CORRUPTED indicates that the buffer contains
absolutely no any data.

SPA_CHUNK_FLAG_CORRUPTED indicates that the buffer has no frame contents
but it can contain other data, for example cursor metadata.

src/plugins/screencast/screencaststream.cpp

@@ -546,7 +546,7 @@ void ScreenCastStream::recordFrame(const QRegion &_damagedRegion)
         uint8_t *data = static_cast<uint8_t *>(spa_data->data);
         if (!data) {
             qCWarning(KWIN_SCREENCAST) << objectName() << "Failed to record frame: invalid buffer data";
-            spa_data->chunk->flags = SPA_CHUNK_FLAG_CORRUPTED;
+            corruptHeader(spa_buffer);
             pw_stream_queue_buffer(m_pwStream, buffer);
             return;
         }
@@ -557,7 +557,7 @@ void ScreenCastStream::recordFrame(const QRegion &_damagedRegion)
 
         if ((stride * size.height()) > spa_data->maxsize) {
             qCDebug(KWIN_SCREENCAST) << objectName() << "Failed to record frame: frame is too big";
-            spa_data->chunk->flags = SPA_CHUNK_FLAG_CORRUPTED;
+            corruptHeader(spa_buffer);
             pw_stream_queue_buffer(m_pwStream, buffer);
             return;
         }
@@ -576,7 +576,7 @@ void ScreenCastStream::recordFrame(const QRegion &_damagedRegion)
         auto dmabuf = m_dmabufDataForPwBuffer.constFind(buffer);
         if (dmabuf == m_dmabufDataForPwBuffer.constEnd()) {
             qCDebug(KWIN_SCREENCAST) << objectName() << "Failed to record frame: no dmabuf data";
-            spa_data->chunk->flags = SPA_CHUNK_FLAG_CORRUPTED;
+            corruptHeader(spa_buffer);
             pw_stream_queue_buffer(m_pwStream, buffer);
             return;
         }
@@ -630,7 +630,7 @@ void ScreenCastStream::recordFrame(const QRegion &_damagedRegion)
         }
     } else {
         qCWarning(KWIN_SCREENCAST, "%s Failed to record frame: invalid buffer type: %d", objectName().toUtf8().constData(), spa_data[0].type);
-        spa_data->chunk->flags = SPA_CHUNK_FLAG_CORRUPTED;
+        corruptHeader(spa_buffer);
         pw_stream_queue_buffer(m_pwStream, buffer);
         return;
     }
@@ -656,6 +656,14 @@ void ScreenCastStream::addHeader(spa_buffer *spaBuffer)
     }
 }
 
+void ScreenCastStream::corruptHeader(spa_buffer *spaBuffer)
+{
+    spa_meta_header *spaHeader = (spa_meta_header *)spa_buffer_find_meta_data(spaBuffer, SPA_META_Header, sizeof(spaHeader));
+    if (spaHeader) {
+        spaHeader->flags = SPA_META_HEADER_FLAG_CORRUPTED;
+    }
+}
+
 void ScreenCastStream::addDamage(spa_buffer *spaBuffer, const QRegion &damagedRegion)
 {
     if (spa_meta *vdMeta = spa_buffer_find_meta(spaBuffer, SPA_META_VideoDamage)) {

src/plugins/screencast/screencaststream.h

@@ -91,6 +91,7 @@ private:
     void coreFailed(const QString &errorMessage);
     void sendCursorData(Cursor *cursor, spa_meta_cursor *spa_cursor);
     void addHeader(spa_buffer *spaBuffer);
+    void corruptHeader(spa_buffer *spaBuffer);
     void addDamage(spa_buffer *spaBuffer, const QRegion &damagedRegion);
     void newStreamParams();
     void enqueue(pw_buffer *buffer);