Present desktop video sequentially through GUI paint acknowledgement

tools/chatgui/src/callwindow.cpp

@@ -44,7 +44,14 @@ public:
         resize(qMin(1100, available.width() * 9 / 10), qMin(800, available.height() * 9 / 10));
     }
     QImage remote, local;
+    CallVideoEngine* engine = nullptr;
+    quint64 serial = 0;
 protected:
+    void hideEvent(QHideEvent* event) override { presented(); QWidget::hideEvent(event); }
+    void changeEvent(QEvent* event) override {
+        QWidget::changeEvent(event);
+        if (isMinimized()) presented();
+    }
     void closeEvent(QCloseEvent* event) override {
         DEBUG_INFO(DEBUG_CATEGORY_CALL, "call video window closed; call continues"); event->accept();
     }
@@ -69,8 +76,12 @@ protected:
             QRect target(QPoint(videoRect.right() - preview.width() - 12, videoRect.top() + 12), preview);
             painter.setPen(QPen(Qt::white, 2)); painter.drawRect(target.adjusted(-1, -1, 1, 1)); painter.drawImage(target, local);
         }
+        painter.end(); presented();
     }
 private:
+    void presented() {
+        if (engine && serial) { engine->imagePresented(serial); serial = 0; }
+    }
     void toggleFullScreen() {
         if (isFullScreen()) { showNormal(); if (!m_geometry.isEmpty()) restoreGeometry(m_geometry); }
         else { m_geometry = saveGeometry(); showFullScreen(); }
@@ -271,6 +282,7 @@ CallWindow::CallWindow(QWidget* parent)
     lay->addWidget(m_bgpPathLabel);
     lay->addWidget(m_statsLabel);
     m_video = new CallVideoEngine(this);
+    m_video->setPresentationDriven(true); m_videoWindow->engine = m_video;
     m_localPreview = new QLabel(this); m_localPreview->setAlignment(Qt::AlignCenter); m_localPreview->hide();
     lay->addWidget(m_localPreview, 0, Qt::AlignHCenter);
     m_videoStatus = new QLabel(this); m_videoStatus->setWordWrap(true); lay->addWidget(m_videoStatus);
@@ -317,10 +329,12 @@ CallWindow::CallWindow(QWidget* parent)
     connect(m_video, &CallVideoEngine::statusChanged, this, [this](const QString& text) {
         m_videoStatus->setText(text); m_videoStatus->setVisible(m_state == Active && !text.isEmpty());
     });
-    connect(m_video, &CallVideoEngine::imageChanged, this, [this](const QImage& image) {
+    connect(m_video, &CallVideoEngine::imageChanged, this, [this](const QImage& image, quint64 serial) {
         bool changed = m_remoteImage.isNull() != image.isNull(); m_remoteImage = image;
-        m_videoWindow->remote = image; m_videoWindow->update();
+        m_videoWindow->remote = image; m_videoWindow->serial = serial; m_videoWindow->update();
         if (changed) updateVideoPresentation();
+        // Скрытое окно продолжает принимать поток, не ждёт невозможного paintEvent.
+        if (!m_videoWindow->isVisible() || m_videoWindow->isMinimized()) m_video->imagePresented(serial);
         update();
     });
     connect(m_video, &CallVideoEngine::localImageChanged, this, [this](const QImage& image) {