1 files changed, 137 insertions, 0 deletions
diff --git a/progs/trivial/clear-undefined.c b/progs/trivial/clear-undefined.c
new file mode 100644
index 0000000000..ce066bf8e6
--- /dev/null
+++ b/progs/trivial/clear-undefined.c
@@ -0,0 +1,137 @@
+/*
+ * glClear + glScissor + Undefined content of framebuffer
+ */
+
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <GL/glut.h>
+
+
+GLenum doubleBuffer;
+GLint Width = 200, Height = 150;
+
+static void Init(void)
+{
+   fprintf(stderr, "GL_RENDERER   = %s\n", (char *) glGetString(GL_RENDERER));
+   fprintf(stderr, "GL_VERSION    = %s\n", (char *) glGetString(GL_VERSION));
+   fprintf(stderr, "GL_VENDOR     = %s\n", (char *) glGetString(GL_VENDOR));
+   fprintf(stderr, "Top right corner should be red\n");
+}
+
+static void Reshape(int width, int height)
+{
+   Width = width;
+   Height = height;
+
+   glViewport(0, 0, (GLint)width, (GLint)height);
+
+   glMatrixMode(GL_PROJECTION);
+   glLoadIdentity();
+   glOrtho(-1.0, 1.0, -1.0, 1.0, -0.5, 1000.0);
+   glMatrixMode(GL_MODELVIEW);
+}
+
+static void Key(unsigned char key, int x, int y)
+{
+    switch (key) {
+      case 27:
+	exit(1);
+      default:
+	glutPostRedisplay();
+	return;
+    }
+
+}
+
+static void Draw(void)
+{
+   glColor4f(1.0, 0.0, 0.0, 1.0);
+   glBegin(GL_QUADS);
+   glVertex2d(0.0, 0.0);
+   glVertex2d(0.0, 1.0);
+   glVertex2d(1.0, 1.0);
+   glVertex2d(1.0, 0.0);
+   glEnd();
+
+   glBegin(GL_QUADS);
+   glVertex2d(0.0,  0.0);
+   glVertex2d(0.0, -1.0);
+   glVertex2d(1.0, -1.0);
+   glVertex2d(1.0,  0.0);
+   glEnd();
+
+   glEnable(GL_SCISSOR_TEST);
+   glClearColor(1, 1, 0, 0);
+   glScissor(Width / 2, 0, Width - Width / 2, Height / 2);
+   glClear(GL_COLOR_BUFFER_BIT);
+
+   glClearColor(0, 0, 1, 0);
+   glScissor(0, Height / 2, Width / 2, Height - Height / 2);
+   glClear(GL_COLOR_BUFFER_BIT);
+   glDisable(GL_SCISSOR_TEST);
+
+   glColor4f(0.0, 1.0, 0.0, 1.0);
+   glBegin(GL_QUADS);
+   glVertex2d( 0.0,  0.0);
+   glVertex2d( 0.0, -1.0);
+   glVertex2d(-1.0, -1.0);
+   glVertex2d(-1.0,  0.0);
+   glEnd();
+
+   glFlush();
+
+   if (doubleBuffer) {
+      glutSwapBuffers();
+   }
+}
+
+static GLenum Args(int argc, char **argv)
+{
+    GLint i;
+
+    doubleBuffer = GL_TRUE;
+
+    for (i = 1; i < argc; i++) {
+        if (strcmp(argv[i], "-sb") == 0) {
+	    doubleBuffer = GL_FALSE;
+	} else if (strcmp(argv[i], "-db") == 0) {
+	    doubleBuffer = GL_TRUE;
+	} else {
+	    fprintf(stderr, "%s (Bad option).\n", argv[i]);
+	    return GL_FALSE;
+	}
+    }
+    return GL_TRUE;
+}
+
+int main(int argc, char **argv)
+{
+    GLenum type;
+
+    glutInit(&argc, argv);
+
+    if (Args(argc, argv) == GL_FALSE) {
+	exit(1);
+    }
+
+    glutInitWindowPosition(0, 0); glutInitWindowSize( Width, Height );
+
+
+    type = GLUT_RGB | GLUT_ALPHA;
+    type |= (doubleBuffer) ? GLUT_DOUBLE : GLUT_SINGLE;
+    glutInitDisplayMode(type);
+
+    if (glutCreateWindow(argv[0]) == GL_FALSE) {
+	exit(1);
+    }
+
+    Init();
+	Reshape(Width, Height);
+
+    glutReshapeFunc(Reshape);
+    glutKeyboardFunc(Key);
+    glutDisplayFunc(Draw);
+    glutMainLoop();
+    return 0;
+}