trying to write Syphon server code in c++ header

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  • #59314

    interwebjill
    Participant

    I am using the Syphon framework to serve video frames to a client. There is one line of code I need to use to serve the frames through the server, and I am stuck trying to write it into my c++ code.

    The Syphon documentation here gives this example:

    
    [myServer publishFrameTexture:myTex textureTarget:GL_TEXTURE_RECTANGLE_EXT imageRegion:NSMakeRect(0, 0, width, height) textureDimensions:NSMakeSize(width, height) flipped:NO];

    How do I incorporate this into my c++ header? I have set my xcode compiler flags so that “Other C Flags” are set to “-x objective-c” and “Other C++ Flags” to “-x objective-c++”.

    To give some context the rest of my code currently looks like this (and it builds):

        class OpencvMat2Syphon {
        
            // hack to call glut to create opengl context (one only so they don't wipe out each other)
            static bool haveGLContext;
            uint texId;
            CGLContextObj ctx;
            static SyphonServer *syphonServer;
        
        public:
        
            OpencvMat2Syphon() {
                
                if (!haveGLContext) {
                    char* str[1];  // glut hack for faking passing CLI parameters from main
                    int argc = 1;
                    str[0] = "app";
                    glutInit(&argc, str);
                    glutCreateWindow("imageGrabber");
                    glutDisplayFunc([]{});
                    glutHideWindow();
                    haveGLContext = true;
                }
                
                ctx = CGLGetCurrentContext();
                std::cout << "cgl context: " << ctx << std::endl;
                SyphonServer *syphonServer = [[SyphonServer alloc] initWithName:@"imageGrabberOutput" context:ctx options:nil];
                
                glGenTextures(1, &texId);
            
                glBindTexture(GL_TEXTURE_2D, texId);
                glTexEnvf( GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE );
                glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST );
                glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST );
            }
        
            ~OpencvMat2Syphon() {
                glDeleteTextures(1, &texId);
            }
        
            uint getTexId() {
                return texId;
            }
        
            void uploadTexture(cv::Mat mat) {
            
                glBindTexture(GL_TEXTURE_2D, texId);
                // can do swizzling/channel-flipping here? see https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glTexImage2D.xhtml
                glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB8, mat.cols, mat.rows, 0, GL_RGB, GL_UNSIGNED_BYTE, mat.data);
        
                
        // ??            [syphonServer publishFrameTexture:texId textureTarget:GL_TEXTURE_2D imageRegion:NSMakeRect(0, 0, 1280, 720) textureDimensions:NSMakeSize(1280, 720) flipped:NO];
    
            }
        };
    
        bool OpencvMat2Syphon::haveGLContext = false;
    #59322

    vade
    Keymaster

    What you need to do use leverage Obj-C++ and make a shim class that bridges your C++ and your Obj-C code, so you can safely call this C++ interface from your C++ app.

    Typically you do this by:

    Make an Obj-C++ wrapper which holds the pure Obj-C classes, state and methods you need.

    You make a pure C++ class which wraps those that Obj-C++ class and only in private interfaces (ie, not public facing in headers etc) the Obj-C code (this isolates your pure C++ land from Obj-C bullshit, memory management and headers)

    Then you call your C++ as normal.

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