qcam: viewfinder: Make the viewfinder hold a reference to a buffer

The viewfinder is currently expected to render frames to the screen
synchronously in the display() function, or at least to copy data so
that the buffer can be queued in a new request when the function
returns. This prevents optimisations when the capture format is
identical to the display format.

Make the viewfinder take ownership of the buffer, and notify of its
release through a signal. The release is currently still synchronous,
this will be addressed in a subsequent patch.

Rename the ViewFinder::display() function to render() to better describe
its purpose, as it's meant to start the rendering and not display the
frame synchronously.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/src/qcam/viewfinder.cpp b/src/qcam/viewfinder.cpp
index b8feabd5..2a35932e 100644
--- a/src/qcam/viewfinder.cpp
+++ b/src/qcam/viewfinder.cpp
@@ -25,8 +25,7 @@ ViewFinder::~ViewFinder()
 	delete image_;
 }
 
-void ViewFinder::display(const libcamera::FrameBuffer *buffer,
-			 MappedBuffer *map)
+void ViewFinder::render(libcamera::FrameBuffer *buffer, MappedBuffer *map)
 {
 	if (buffer->planes().size() != 1) {
 		qWarning() << "Multi-planar buffers are not supported";
@@ -44,6 +43,8 @@ void ViewFinder::display(const libcamera::FrameBuffer *buffer,
 	converter_.convert(static_cast<unsigned char *>(map->memory),
 			   buffer->metadata().planes[0].bytesused, image_);
 	update();
+
+	renderComplete(buffer);
 }
 
 QImage ViewFinder::getCurrentImage()