PenLayer: Use the correct context for FBO creation

Author: adazem009

src/penlayer.cpp

@@ -68,7 +68,14 @@ void PenLayer::setEngine(libscratchcpp::IEngine *newEngine)
 
     m_engine = newEngine;
 
-    if (m_engine && QOpenGLContext::currentContext()) {
+    if (!m_glCtx) {
+        m_glCtx = QOpenGLContext::currentContext();
+
+        if (m_glCtx)
+            m_surface = m_glCtx->surface();
+    }
+
+    if (m_engine && m_glCtx) {
         m_projectPenLayers[m_engine] = this;
 
         if (!m_painter)
@@ -428,6 +435,10 @@ void PenLayer::addPenLayer(libscratchcpp::IEngine *engine, IPenLayer *penLayer)
 
 QNanoQuickItemPainter *PenLayer::createItemPainter() const
 {
+    m_glCtx = QOpenGLContext::currentContext();
+    Q_ASSERT(m_glCtx);
+    m_surface = m_glCtx->surface();
+    Q_ASSERT(m_surface);
     return new PenLayerPainter;
 }
 
@@ -441,9 +452,17 @@ void PenLayer::geometryChange(const QRectF &newGeometry, const QRectF &oldGeomet
 
 void PenLayer::createFbo()
 {
-    if (!QOpenGLContext::currentContext() || !m_engine)
+    if (!m_glCtx || !m_surface || !m_engine || !m_glF)
         return;
 
+    QOpenGLContext *oldCtx = QOpenGLContext::currentContext();
+    QSurface *oldSurface = oldCtx->surface();
+
+    if (oldCtx != m_glCtx) {
+        oldCtx->doneCurrent();
+        m_glCtx->makeCurrent(m_surface);
+    }
+
     QOpenGLFramebufferObjectFormat fboFormat;
     fboFormat.setAttachment(QOpenGLFramebufferObject::CombinedDepthStencil);
 
@@ -456,6 +475,11 @@ void PenLayer::createFbo()
     m_fbo.reset(newFbo);
     m_texture = Texture(m_fbo->texture(), m_fbo->size());
     m_scale = width() / m_engine->stageWidth();
+
+    if (oldCtx != m_glCtx) {
+        m_glCtx->doneCurrent();
+        oldCtx->makeCurrent(oldSurface);
+    }
 }
 
 void PenLayer::updateTexture()

src/penlayer.h

@@ -65,6 +65,8 @@ class PenLayer : public IPenLayer
         libscratchcpp::IEngine *m_engine = nullptr;
         bool m_hqPen = false;
         std::unique_ptr<QOpenGLFramebufferObject> m_fbo;
+        mutable QOpenGLContext *m_glCtx = nullptr;
+        mutable QSurface *m_surface = nullptr;
         double m_scale = 1;
         std::unique_ptr<QNanoPainter> m_painter;
         std::unique_ptr<QOpenGLExtraFunctions> m_glF;