NSView to ofTexture

view_to_tex.cpp

void viewToTex(NSView * view, ofTexture& tex) {
    // this is based on listing 11-3 at
    // https://developer.apple.com/library/content/documentation/GraphicsImaging/Conceptual/OpenGL-MacProgGuide/opengl_texturedata/opengl_texturedata.html
    
    NSBitmapImageRep * bitmap = [view bitmapImageRepForCachingDisplayInRect:view.visibleRect];
    [view cacheDisplayInRect:view.visibleRect toBitmapImageRep:bitmap];
    
    glPixelStorei(GL_UNPACK_ROW_LENGTH, bitmap.bytesPerRow / bitmap.samplesPerPixel);
    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
    
    if (tex.getTextureData().textureID == 0) {
        throw std::runtime_error("texture isn't allocated");
    }
    
    glBindTexture(GL_TEXTURE_RECTANGLE_ARB, tex.getTextureData().textureID);
    glTexParameteri(GL_TEXTURE_RECTANGLE_ARB, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    
    if(!bitmap.isPlanar && (bitmap.samplesPerPixel == 3 || bitmap.samplesPerPixel == 4)) {
        glTexImage2D(GL_TEXTURE_RECTANGLE_ARB,
                     0,
                     bitmap.samplesPerPixel == 4 ? GL_RGBA8 : GL_RGB8,
                     bitmap.pixelsWide,
                     bitmap.pixelsHigh,
                     0,
                     bitmap.samplesPerPixel == 4 ? GL_RGBA : GL_RGB,
                     GL_UNSIGNED_BYTE,
                     bitmap.bitmapData);
    } else {
        throw std::runtime_error("unsupported bitmap data");
    }
    
    // hail-mary reset back to default
    glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
    glPixelStorei(GL_UNPACK_ALIGNMENT, 4);
}

z_usage.cpp

NSView * view = ...;
    
renderedTexture = ofTexture();
renderedTexture.allocate(512, 512, GL_RGBA);
viewToTex(view, renderedTexture);