trivial/tri-viewport.c - add guide lines, more triangles, make interactive

This is becoming more like a test than a trivial/ example.

progs/trivial/tri-viewport.c

@@ -29,6 +29,10 @@
 
 GLenum doubleBuffer = 1;
 int win;
+static float tx = 0;
+static float ty = 0;
+static float tw = 250;
+static float th = 250;
 
 static void Init(void)
 {
@@ -42,15 +46,11 @@ static void Init(void)
 
 static void Reshape(int width, int height)
 {
-   glViewport(width / -2.0, height / -2.0, width, height);
+   tw = width;
-
+   th = height;
-   glMatrixMode(GL_PROJECTION);
-   glLoadIdentity();
-   glOrtho(-1.0, 1.0, -1.0, 1.0, -0.5, 1000.0);
-   glMatrixMode(GL_MODELVIEW);
-   glLoadIdentity();
 }
 
+
 static void Key(unsigned char key, int x, int y)
 {
    switch (key) {
@@ -62,19 +62,91 @@ static void Key(unsigned char key, int x, int y)
    }
 }
 
+
 static void Draw(void)
 {
+   int i;
+
+   fprintf(stderr, "%f %f\n", tx, ty);
+   fflush(stderr);
+
+   glMatrixMode(GL_PROJECTION);
+   glLoadIdentity();
+   glOrtho(-1.0, 1.0, -1.0, 1.0, -0.5, 1000.0);
+   glMatrixMode(GL_MODELVIEW);
+
    glClear(GL_COLOR_BUFFER_BIT); 
 
-   glBegin(GL_TRIANGLES);
+   glViewport(0, 0, tw, th);
-   glColor3f(.8,0,0); 
+
-   glVertex3f(-0.9,  0.9, -30.0);
+   glBegin(GL_LINES);
-   glColor3f(0,.9,0); 
+   glColor3f(1,1,0); 
-   glVertex3f( 0.9,  0.9, -30.0);
+   glVertex3f(-1, 0, -30.0);
-   glColor3f(0,0,.7); 
+   glVertex3f(1, 0, -30.0);
-   glVertex3f( 0.0, -0.9, -30.0);
+
+   glVertex3f(0,  -1, -30.0);
+   glVertex3f(0,  1, -30.0);
    glEnd();
 
+
+   /* 
+    */
+   glViewport(tx, ty, tw, th);
+
+
+   glBegin(GL_TRIANGLES);
+   glColor3f(1,0,0); 
+   glVertex3f(-1, -1, -30.0);
+   glVertex3f(0, -1, -30.0);
+   glVertex3f(-.5,  -.5, -30.0);
+
+   glColor3f(1,1,1);
+   glVertex3f(0, -1, -30.0);
+   glVertex3f(1, -1, -30.0);
+   glVertex3f(.5,  -.5, -30.0);
+
+   glVertex3f(-.5, -.5, -30.0);
+   glVertex3f(.5, -.5, -30.0);
+   glVertex3f(0,  0, -30.0);
+
+
+   glColor3f(0,1,0); 
+   glVertex3f(1, 1, -30.0);
+   glVertex3f(0, 1, -30.0);
+   glVertex3f(.5,  .5, -30.0);
+
+   glColor3f(1,1,1);
+   glVertex3f(0, 1, -30.0);
+   glVertex3f(-1, 1, -30.0);
+   glVertex3f(-.5,  .5, -30.0);
+
+   glVertex3f(.5, .5, -30.0);
+   glVertex3f(-.5, .5, -30.0);
+   glVertex3f( 0,  0, -30.0);
+
+   glEnd();
+
+
+   glViewport(0, 0, tw, th);
+
+   glBegin(GL_LINES);
+   glColor3f(.5,.5,0); 
+   for (i = -10; i < 10; i++) {
+      float f = i / 10.0;
+
+      if (i == 0)
+         continue;
+
+      glVertex3f(-1, f, -30.0);
+      glVertex3f(1, f, -30.0);
+
+      glVertex3f(f, -1, -30.0);
+      glVertex3f(f, 1, -30.0);
+   }
+   glEnd();
+
+
+
    glFlush();
 
    if (doubleBuffer) {
@@ -86,6 +158,13 @@ static GLenum Args(int argc, char **argv)
 {
    GLint i;
 
+   if (getenv("VPX"))
+      tx = atof(getenv("VPX"));
+
+   if (getenv("VPY"))
+      ty = atof(getenv("VPY"));
+
+
    for (i = 1; i < argc; i++) {
       if (strcmp(argv[i], "-sb") == 0) {
          doubleBuffer = GL_FALSE;
@@ -99,6 +178,30 @@ static GLenum Args(int argc, char **argv)
    return GL_TRUE;
 }
 
+
+static void
+special(int k, int x, int y)
+{
+   switch (k) {
+   case GLUT_KEY_UP:
+      ty += 1.0;
+      break;
+   case GLUT_KEY_DOWN:
+      ty -= 1.0;
+      break;
+   case GLUT_KEY_LEFT:
+      tx -= 1.0;
+      break;
+   case GLUT_KEY_RIGHT:
+      tx += 1.0;
+      break;
+   default:
+      return;
+   }
+   glutPostRedisplay();
+}
+
+
 int main(int argc, char **argv)
 {
    GLenum type;
@@ -124,6 +227,7 @@ int main(int argc, char **argv)
 
    glutReshapeFunc(Reshape);
    glutKeyboardFunc(Key); 
+   glutSpecialFunc(special);
    glutDisplayFunc(Draw);
    glutMainLoop();
    return 0;