qt: Add overload protection to renderers

Added atomic_flags for renderer buffers to prevent concurrent usage and
overloading the renderer with draw requests when it's busy.

src/qt/qt_hardwarerenderer.cpp

@@ -1,5 +1,6 @@
 #include "qt_hardwarerenderer.hpp"
 #include <QApplication>
+#include <atomic>
 
 extern "C" {
 #include <86box/86box.h>
@@ -34,10 +35,11 @@ void HardwareRenderer::setRenderType(RenderType type) {
     setFormat(format);
 }
 
-void HardwareRenderer::onBlit(const QImage& img, int x, int y, int w, int h) {
+void HardwareRenderer::onBlit(const QImage& img, int x, int y, int w, int h, std::atomic_flag* in_use) {
     image = img;
     source.setRect(x, y, w, h);
     update();
+    in_use->clear();
 }
 
 void HardwareRenderer::resizeEvent(QResizeEvent *event) {

src/qt/qt_hardwarerenderer.hpp

@@ -43,7 +43,7 @@ public:
     void setRenderType(RenderType type);
 
 public slots:
-    void onBlit(const QImage& img, int, int, int, int);
+    void onBlit(const QImage& img, int, int, int, int, std::atomic_flag* in_use);
 
 protected:
     void resizeEvent(QResizeEvent *event) override;

src/qt/qt_rendererstack.cpp

@@ -27,6 +27,11 @@ RendererStack::RendererStack(QWidget *parent) :
     imagebufs = QVector<QImage>(2);
     imagebufs[0] = QImage{QSize(2048 + 64, 2048 + 64), QImage::Format_RGB32};
     imagebufs[1] = QImage{QSize(2048 + 64, 2048 + 64), QImage::Format_RGB32};
+
+    buffers_in_use = std::vector<std::atomic_flag>(2);
+    buffers_in_use[0].clear();
+    buffers_in_use[1].clear();
+
 #ifdef WAYLAND
     if (QApplication::platformName().contains("wayland")) {
         wl_init();
@@ -165,7 +170,7 @@ void RendererStack::leaveEvent(QEvent* event)
 // called from blitter thread
 void RendererStack::blit(int x, int y, int w, int h)
 {
-    if ((w <= 0) || (h <= 0) || (w > 2048) || (h > 2048) || (buffer32 == NULL))
+    if ((w <= 0) || (h <= 0) || (w > 2048) || (h > 2048) || (buffer32 == NULL) || buffers_in_use[currentBuf].test_and_set())
     {
         video_blit_complete();
         return;
@@ -182,7 +187,7 @@ void RendererStack::blit(int x, int y, int w, int h)
         video_screenshot((uint32_t *)imagebits, 0, 0, 2048 + 64);
     }
     video_blit_complete();
-    blitToRenderer(imagebufs[currentBuf], sx, sy, sw, sh);
+    blitToRenderer(imagebufs[currentBuf], sx, sy, sw, sh, &buffers_in_use[currentBuf]);
     currentBuf = (currentBuf + 1) % 2;
 }
 
@@ -190,11 +195,11 @@ void RendererStack::on_RendererStack_currentChanged(int arg1) {
     disconnect(this, &RendererStack::blitToRenderer, nullptr, nullptr);
     switch (arg1) {
     case 0:
-        connect(this, &RendererStack::blitToRenderer, dynamic_cast<SoftwareRenderer*>(currentWidget()), &SoftwareRenderer::onBlit);
+        connect(this, &RendererStack::blitToRenderer, dynamic_cast<SoftwareRenderer*>(currentWidget()), &SoftwareRenderer::onBlit, Qt::QueuedConnection);
         break;
     case 1:
     case 2:
-        connect(this, &RendererStack::blitToRenderer, dynamic_cast<HardwareRenderer*>(currentWidget()), &HardwareRenderer::onBlit);
+        connect(this, &RendererStack::blitToRenderer, dynamic_cast<HardwareRenderer*>(currentWidget()), &HardwareRenderer::onBlit, Qt::QueuedConnection);
         break;
     }
 }

src/qt/qt_rendererstack.hpp

@@ -4,6 +4,8 @@
 #include <QStackedWidget>
 #include <QKeyEvent>
 #include <QEvent>
+#include <vector>
+#include <atomic>
 
 namespace Ui {
 class RendererStack;
@@ -32,7 +34,7 @@ public:
     }
 
 signals:
-    void blitToRenderer(const QImage& img, int, int, int, int);
+    void blitToRenderer(const QImage& img, int, int, int, int, std::atomic_flag* in_use);
 
 public slots:
     void blit(int x, int y, int w, int h);
@@ -57,6 +59,9 @@ private:
     // when calling bits();
     int currentBuf = 0;
     QVector<QImage> imagebufs;
+
+    /* atomic flag for each buffer to not overload the renderer */
+    std::vector<std::atomic_flag> buffers_in_use;
 };
 
 #endif // QT_RENDERERCONTAINER_HPP

src/qt/qt_softwarerenderer.cpp

@@ -7,10 +7,11 @@ void SoftwareRenderer::paintEvent(QPaintEvent *event) {
     onPaint(this);
 }
 
-void SoftwareRenderer::onBlit(const QImage& img, int x, int y, int w, int h) {
+void SoftwareRenderer::onBlit(const QImage& img, int x, int y, int w, int h, std::atomic_flag* in_use) {
     image = img;
     source.setRect(x, y, w, h);
     update();
+    in_use->clear();
 }
 
 void SoftwareRenderer::resizeEvent(QResizeEvent *event) {

src/qt/qt_softwarerenderer.hpp

@@ -2,6 +2,7 @@
 #define SOFTWARERENDERER_HPP
 
 #include <QWidget>
+#include <atomic>
 #include "qt_renderercomon.hpp"
 
 class SoftwareRenderer : public QWidget, public RendererCommon
@@ -12,7 +13,7 @@ public:
 
     void paintEvent(QPaintEvent *event) override;
 public slots:
-    void onBlit(const QImage& img, int, int, int, int);
+    void onBlit(const QImage& img, int, int, int, int, std::atomic_flag* in_use);
 
 protected:
     void resizeEvent(QResizeEvent *event) override;