139 lines
2.7 KiB
C
139 lines
2.7 KiB
C
/*
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* glClear + glScissor + Undefined content of framebuffer
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*/
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#include <stdio.h>
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#include <string.h>
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#include <stdlib.h>
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#include <GL/glut.h>
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GLenum doubleBuffer;
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GLint Width = 200, Height = 150;
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static void Init(void)
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{
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fprintf(stderr, "GL_RENDERER = %s\n", (char *) glGetString(GL_RENDERER));
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fprintf(stderr, "GL_VERSION = %s\n", (char *) glGetString(GL_VERSION));
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fprintf(stderr, "GL_VENDOR = %s\n", (char *) glGetString(GL_VENDOR));
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fprintf(stderr, "Top right corner should be red\n");
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fflush(stderr);
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}
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static void Reshape(int width, int height)
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{
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Width = width;
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Height = height;
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glViewport(0, 0, (GLint)width, (GLint)height);
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glMatrixMode(GL_PROJECTION);
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glLoadIdentity();
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glOrtho(-1.0, 1.0, -1.0, 1.0, -0.5, 1000.0);
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glMatrixMode(GL_MODELVIEW);
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}
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static void Key(unsigned char key, int x, int y)
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{
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switch (key) {
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case 27:
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exit(1);
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default:
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glutPostRedisplay();
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return;
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}
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}
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static void Draw(void)
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{
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glColor4f(1.0, 0.0, 0.0, 1.0);
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glBegin(GL_QUADS);
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glVertex2d(0.0, 0.0);
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glVertex2d(0.0, 1.0);
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glVertex2d(1.0, 1.0);
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glVertex2d(1.0, 0.0);
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glEnd();
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glBegin(GL_QUADS);
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glVertex2d(0.0, 0.0);
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glVertex2d(0.0, -1.0);
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glVertex2d(1.0, -1.0);
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glVertex2d(1.0, 0.0);
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glEnd();
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glEnable(GL_SCISSOR_TEST);
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glClearColor(1, 1, 0, 0);
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glScissor(Width / 2, 0, Width - Width / 2, Height / 2);
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glClear(GL_COLOR_BUFFER_BIT);
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glClearColor(0, 0, 1, 0);
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glScissor(0, Height / 2, Width / 2, Height - Height / 2);
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glClear(GL_COLOR_BUFFER_BIT);
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glDisable(GL_SCISSOR_TEST);
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glColor4f(0.0, 1.0, 0.0, 1.0);
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glBegin(GL_QUADS);
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glVertex2d( 0.0, 0.0);
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glVertex2d( 0.0, -1.0);
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glVertex2d(-1.0, -1.0);
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glVertex2d(-1.0, 0.0);
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glEnd();
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glFlush();
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if (doubleBuffer) {
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glutSwapBuffers();
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}
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}
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static GLenum Args(int argc, char **argv)
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{
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GLint i;
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doubleBuffer = GL_TRUE;
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for (i = 1; i < argc; i++) {
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if (strcmp(argv[i], "-sb") == 0) {
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doubleBuffer = GL_FALSE;
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} else if (strcmp(argv[i], "-db") == 0) {
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doubleBuffer = GL_TRUE;
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} else {
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fprintf(stderr, "%s (Bad option).\n", argv[i]);
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return GL_FALSE;
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}
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}
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return GL_TRUE;
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}
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int main(int argc, char **argv)
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{
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GLenum type;
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glutInit(&argc, argv);
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if (Args(argc, argv) == GL_FALSE) {
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exit(1);
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}
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glutInitWindowPosition(0, 0); glutInitWindowSize( Width, Height );
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type = GLUT_RGB | GLUT_ALPHA;
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type |= (doubleBuffer) ? GLUT_DOUBLE : GLUT_SINGLE;
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glutInitDisplayMode(type);
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if (glutCreateWindow(argv[0]) == GL_FALSE) {
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exit(1);
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}
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Init();
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Reshape(Width, Height);
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glutReshapeFunc(Reshape);
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glutKeyboardFunc(Key);
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glutDisplayFunc(Draw);
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glutMainLoop();
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return 0;
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}
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