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POopengl rubberbanded box not showing
 

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  1. POopengl rubberbanded box not showing
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    <p>I'm trying to draw a selection box over an image drawn using glDrawPixels, but I cannot get it to show. In order to represent the coordinates of the box, I have 4 global integers that I update on mouse actions (the first 2 on click, the others when the mouse is dragged), which I then use in the drawing function. I'm sure that the drawing function is called when the mouse gets dragged, and that the four values at least get updated, since I tried printing them every time the drawing function gets called. The OpenGL calls I have in the main are:</p> <pre><code>glutInit(&amp;argc, argv); glutInitWindowSize(WINDOW_DIM, WINDOW_DIM); glutInitWindowPosition(0, 0); glutInitDisplayMode(GLUT_RGB|GLUT_DOUBLE); glutCreateWindow("Window"); glutDisplayFunc(display); glutMouseFunc(mouse); glutMotionFunc(motion); glClearColor(0.0, 0.0, 0.0, 1.0); glDisable(GL_DEPTH_TEST); glutMainLoop(); </code></pre> <p>and my display function:</p> <pre><code>void display() { printf("calling display\n"); for(unsigned int i=0; i&lt;WINDOW_DIM*WINDOW_DIM; ++i) { pixels[i]=colors[img[i]]; } glClear(GL_COLOR_BUFFER_BIT); glDrawPixels(WINDOW_DIM, WINDOW_DIM, GL_RGB, GL_FLOAT, (float*)pixels); glutSwapBuffers(); if(upd_xmin!=0 || upd_ymin!=0 || upd_xmax!=0 || upd_ymax!=0) { glDrawBuffer(GL_FRONT); glLogicOp(GL_XOR); glEnable(GL_COLOR_LOGIC_OP); printf("drawing selection\n"); printf("coords %d %d %d %d\n", upd_xmin, upd_ymin, upd_xmax, upd_ymax); glColor3f(1.0, 1.0, 1.0); glLineWidth(3.0); glBegin(GL_LINE_LOOP); glVertex2i(upd_xmin, upd_ymin); glVertex2i(upd_xmin, upd_ymax); glVertex2i(upd_xmax, upd_ymax); glVertex2i(upd_xmax, upd_ymin); glEnd(); glDisable(GL_COLOR_LOGIC_OP); glDrawBuffer(GL_BACK); } } </code></pre> <p>As I said, I don't think the problem is with the mouse and motion function, seeing how the coordinates of the box (the upd_x and upd_y variables in the code above) get updated when there's a mouse event, but if needed I can post those as well. </p>
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