create failsafe window for always maintaining reference to shared context, fixes runtime error when removing external window objects from patch if only one present

Author: d3cod3

src/ofxVisualProgramming.cpp

@@ -159,6 +159,9 @@ void ofxVisualProgramming::setup(ofxImGui::Gui* _guiRef, string release){
     canvas.toggleOfCam();
     easyCam.enableOrtho();
 
+    // create failsafe window for always maintaining reference to shared context
+    setupFailsafeWindow();
+
     // RESET TEMP FOLDER
     resetTempFolder();
 
@@ -187,6 +190,28 @@ void ofxVisualProgramming::setup(ofxImGui::Gui* _guiRef, string release){
 
 }
 
+//--------------------------------------------------------------
+void ofxVisualProgramming::setupFailsafeWindow(){
+    ofGLFWWindowSettings settings;
+#if defined(OFXVP_GL_VERSION_MAJOR) && defined(OFXVP_GL_VERSION_MINOR)
+    settings.setGLVersion(OFXVP_GL_VERSION_MAJOR,OFXVP_GL_VERSION_MINOR);
+#else
+    settings.setGLVersion(3,2);
+#endif
+    settings.shareContextWith = mainWindow;
+    settings.decorated = true;
+    settings.resizable = false;
+    settings.visible = false;
+    settings.setPosition(ofDefaultVec2(0,0));
+    settings.setSize(10,10);
+
+    failsafeWindow = dynamic_pointer_cast<ofAppGLFWWindow>(ofCreateWindow(settings));
+    failsafeWindow->setVerticalSync(false);
+    failsafeWindow->setWindowPosition(0,0);
+
+    glfwSetWindowCloseCallback(failsafeWindow->getGLFWWindow(),GL_FALSE);
+}
+
 //--------------------------------------------------------------
 void ofxVisualProgramming::update(){
 

src/ofxVisualProgramming.h

@@ -60,6 +60,7 @@ class ofxVisualProgramming : public pdsp::Wrapper {
 
     void            setRetina(bool retina);
     void            setup(ofxImGui::Gui* guiRef = nullptr, string release="");
+    void            setupFailsafeWindow();
     void            update();
     void            updateCanvasViewport();
     void            draw();
@@ -210,6 +211,8 @@ class ofxVisualProgramming : public pdsp::Wrapper {
 private:
     void audioProcess(float *input, int bufferSize, int nChannels);
 
-    mutable ofMutex         vp_mutex;
+    mutable ofMutex                 vp_mutex;
+
+    shared_ptr<ofAppGLFWWindow>     failsafeWindow;
 
 };