futzing around with opengl

Makefile

@@ -1,5 +1,6 @@
 all:
 	cd ./basics && $(MAKE)
+	cd ./opengl && $(MAKE)
 
 
 .PHONY: all

opengl/Makefile

@@ -0,0 +1,19 @@
+CPPC := g++
+BINDIR := $(PWD)/bin
+
+ALL_TARGETS = $(BINDIR)/demo
+
+
+all: $(ALL_TARGETS)
+
+
+clean:
+	rm -vf ./bin/*
+
+
+$(BINDIR)/demo:
+	cd src && \
+	gcc -o $(BINDIR)/demo demo.c -lX11 -lGL -lGLU
+
+
+.PHONY: all clean

opengl/src/demo.c

@@ -0,0 +1,92 @@
+#include<stdio.h>
+#include<stdlib.h>
+#include<X11/X.h>
+#include<X11/Xlib.h>
+#include<GL/gl.h>
+#include<GL/glx.h>
+#include<GL/glu.h>
+
+Display                 *dpy;
+Window                  root;
+GLint                   att[] = { GLX_RGBA, GLX_DEPTH_SIZE, 24, GLX_DOUBLEBUFFER, None };
+XVisualInfo             *vi;
+Colormap                cmap;
+XSetWindowAttributes    swa;
+Window                  win;
+GLXContext              glc;
+XWindowAttributes       gwa;
+XEvent                  xev;
+
+
+void DrawAQuad() {
+    glClearColor(1.0, 1.0, 1.0, 1.0);
+    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+
+    glMatrixMode(GL_PROJECTION);
+    glLoadIdentity();
+    glOrtho(-1., 1., -1., 1., 1., 20.);
+
+    glMatrixMode(GL_MODELVIEW);
+    glLoadIdentity();
+    gluLookAt(0., 0., 10., 0., 0., 0., 0., 1., 0.);
+
+    glBegin(GL_QUADS);
+    glColor3f(1., 0., 0.); glVertex3f(-.75, -.75, 0.);
+    glColor3f(0., 1., 0.); glVertex3f( .75, -.75, 0.);
+    glColor3f(0., 0., 1.); glVertex3f( .75,  .75, 0.);
+    glColor3f(1., 1., 0.); glVertex3f(-.75,  .75, 0.);
+    glEnd();
+}
+
+int main(int argc, char *argv[]) {
+
+    dpy = XOpenDisplay(NULL);
+
+    if(dpy == NULL) {
+        printf("\n\tcannot connect to X server\n\n");
+        exit(0);
+    }
+
+    root = DefaultRootWindow(dpy);
+
+    vi = glXChooseVisual(dpy, 0, att);
+
+    if(vi == NULL) {
+        printf("\n\tno appropriate visual found\n\n");
+        exit(0); } 
+    else {
+        printf("\n\tvisual %p selected\n", (void *)vi->visualid); } /* %p creates hexadecimal output like in glxinfo */
+
+    cmap = XCreateColormap(dpy, root, vi->visual, AllocNone);
+
+    swa.colormap = cmap;
+    swa.event_mask = ExposureMask | KeyPressMask;
+
+    win = XCreateWindow(dpy, root, 0, 0, 600, 600, 0, vi->depth, InputOutput, vi->visual, CWColormap | CWEventMask, &swa);
+
+    XMapWindow(dpy, win);
+
+    XStoreName(dpy, win, "VERY SIMPLE APPLICATION");
+
+    glc = glXCreateContext(dpy, vi, NULL, GL_TRUE);
+    glXMakeCurrent(dpy, win, glc);
+
+    glEnable(GL_DEPTH_TEST); 
+
+    while(1) {
+        XNextEvent(dpy, &xev);
+
+        if(xev.type == Expose) {
+            XGetWindowAttributes(dpy, win, &gwa);
+            glViewport(0, 0, gwa.width, gwa.height);
+            DrawAQuad(); 
+            glXSwapBuffers(dpy, win); }
+
+        else if(xev.type == KeyPress) {
+            glXMakeCurrent(dpy, None, NULL);
+            glXDestroyContext(dpy, glc);
+            XDestroyWindow(dpy, win);
+            XCloseDisplay(dpy);
+            exit(0); }
+    } /* this closes while(1) { */
+} /* this is the } which closes int main(int argc, char *argv[]) { */