qt: Refactor renderers buffer ownership

Invert the way buffers are created; make renderer create buffers for
renderer stack.
Use QImage bits as the buffer for software renderer.

src/qt/qt_rendererstack.hpp

@@ -7,7 +7,7 @@
 #include <memory>
 #include <vector>
 #include <atomic>
-#include <array>
+#include <tuple>
 
 namespace Ui {
 class RendererStack;
@@ -46,7 +46,7 @@ public:
 
     RendererCommon* rendererWindow{nullptr};
 signals:
-    void blitToRenderer(const std::unique_ptr<uint8_t>* img, int, int, int, int, std::atomic_flag* in_use);
+    void blitToRenderer(int buf_idx, int x, int y, int w, int h);
 
 public slots:
     void blit(int x, int y, int w, int h);
@@ -64,13 +64,10 @@ private:
     int x, y, w, h, sx, sy, sw, sh;
 
     int currentBuf = 0;
-    std::array<std::unique_ptr<uint8_t>, 2> imagebufs;
+    std::vector<std::tuple<uint8_t*, std::atomic_flag*>> imagebufs;
 
     std::unique_ptr<QWidget> current;
 
-    /* atomic flag for each buffer to not overload the renderer */
-    std::vector<std::atomic_flag> buffers_in_use;
-
     friend class MainWindow;
 };