GLFW simple triangle is lost? - macos

Question

I modified the "Simple example" example in GLFW3.0.4 in Mac OSX 10.8 as an XCode 4.6 project (runs fine when unchanged). I am having a (2D) rectangle drawn with an external library (which draws via shaders). I can see the rectangle but If I draw the sample triangle (immediate drawn) before it, the triangle is seen in the first splash (frame) and then it is lost. If I try to draw it after, the triangle is never seen. I can only see the rectangle and I don't know what settings/states the library is changing!
I tried to inspect the application with OpenGL Profiler. Stopped before CGLFlushDrawable and could not find the triangle in any of the buffers (front, back, depth, stencil).
Am I doing something (prominently) wrong? The profiler allows only gl-function breakpoints. How can I debug this (more efficiently) and find the problem.
Here is (much of the changed parts of) the code:
void glfw2DViewport(GLFWwindow * window) {
float ratio;
int width, height;
glfwGetFramebufferSize(window, &width, &height);
ratio = width / (float) height;
glViewport(0, 0, width, height);
glClearColor(0.8, 0.8, 0.8, 1.0); // Lets see if something black is drawn!!
glClear(GL_COLOR_BUFFER_BIT);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
// eye is at 0,0,0 looking to positive Z, -1(behind) to 1 are clipping planes:
// https://www.opengl.org/sdk/docs/man2/xhtml/glOrtho.xml
glOrtho(ratio, -ratio, -1.f, 1.f, 1.0f, -1.f);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
// ----- 2D settings -----
glfwSwapInterval(1);
glEnable(GL_SMOOTH);
glDisable(GL_DEPTH_TEST);
//glDisable(GL_STENCIL_TEST); // Disabling changed nothing!!
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glLineWidth(5.0f);
glEnable(GL_LINE_SMOOTH);
glPointSize(5.0f);
glEnable(GL_POINT_SMOOTH);
}
int main(void) {
GLFWwindow* window;
glfwSetErrorCallback(error_callback);
if (!glfwInit())
exit(EXIT_FAILURE);
window = glfwCreateWindow(640, 480, "Simple example", NULL, NULL);
if (!window) {
glfwTerminate();
exit(EXIT_FAILURE);
}
glfwMakeContextCurrent(window);
glfw2DViewport(window);
//...
while (!glfwWindowShouldClose(window)) {
glMatrixMode(GL_MODELVIEW_MATRIX);
glLoadIdentity();
glClear(GL_COLOR_BUFFER_BIT);
//drawUnitTriangle(); // can be seen just in the first frame!
glPushClientAttrib(GL_CLIENT_ALL_ATTRIB_BITS); // A vain attempt?
glPushAttrib(GL_ALL_ATTRIB_BITS); // Another vain attempt??
external_library_identity_matrix();
external_library_rectangle(POS,RED);
external_library_flush();
glPopAttrib();
glPopClientAttrib();
// Other vain attempts:
glfwMakeContextCurrent(window);
glMatrixMode(GL_MODELVIEW_MATRIX);
glLoadIdentity();
drawUnitTriangle(); // Nothing is Drawn!!
glfwSwapBuffers(window);
glfwPollEvents();
}
glfwDestroyWindow(window);
glfwTerminate();
exit(EXIT_SUCCESS);
}

Answer 1

Are you sure the posted code is exactly what you are building with? If that's true, please check the argument of glMatrixMode() it should be GL_MODELVIEW, not GL_MODELVIEW_MATRIX. There are two places where you set it like this.
Since you already have glfw2DViewport(), why don't you put it in the while loop and delete other model view setting codes?