gfx.cpp

/*
A simple graphics library for CSE 20211 by Douglas Thain
For complete documentation, see:
http://www.nd.edu/~dthain/courses/cse20211/fall2011/gfx
Version 3, 11/07/2012 - Now much faster at changing colors rapidly.
Version 2, 9/23/2011 - Fixes a bug that could result in jerky animation.
*/

#include <X11/Xlib.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>

#include "gfx.h"

/*
gfx_open creates several X11 objects, and stores them in globals
for use by the other functions in the library.
*/

static Display *gfx_display=0;
static Window  gfx_window;
static GC      gfx_gc;
static Colormap gfx_colormap;
static int      gfx_fast_color_mode = 0;

/* These values are saved by gfx_wait then retrieved later by gfx_xpos and gfx_ypos. */

static int saved_xpos = 0;
static int saved_ypos = 0;

/* Open a new graphics window. */

void gfx_open( int width, int height, const char *title )
{
    gfx_display = XOpenDisplay(0);
    if(!gfx_display) {
        fprintf(stderr,"gfx_open: unable to open the graphics window.\n");
        exit(1);
    }

    Visual *visual = DefaultVisual(gfx_display,0);
    if(visual && visual->c_class==TrueColor) {
        gfx_fast_color_mode = 1;
    } else {
        gfx_fast_color_mode = 0;
    }

    int blackColor = BlackPixel(gfx_display, DefaultScreen(gfx_display));
    int whiteColor = WhitePixel(gfx_display, DefaultScreen(gfx_display));

    gfx_window = XCreateSimpleWindow(gfx_display, DefaultRootWindow(gfx_display), 0, 0, width, height, 0, blackColor, blackColor);

    XSetWindowAttributes attr;
    attr.backing_store = Always;

    XChangeWindowAttributes(gfx_display,gfx_window,CWBackingStore,&attr);

    XStoreName(gfx_display,gfx_window,title);

    XSelectInput(gfx_display, gfx_window, StructureNotifyMask|KeyPressMask|ButtonPressMask);

    XMapWindow(gfx_display,gfx_window);

    gfx_gc = XCreateGC(gfx_display, gfx_window, 0, 0);

    gfx_colormap = DefaultColormap(gfx_display,0);

    XSetForeground(gfx_display, gfx_gc, whiteColor);

    // Wait for the MapNotify event

    for(;;) {
        XEvent e;
        XNextEvent(gfx_display, &e);
        if (e.type == MapNotify)
            break;
    }
}

/* Draw a single point at (x,y) */

void gfx_point( int x, int y )
{
    XDrawPoint(gfx_display,gfx_window,gfx_gc,x,y);
}

/* Draw a line from (x1,y1) to (x2,y2) */

void gfx_line( int x1, int y1, int x2, int y2 )
{
    XDrawLine(gfx_display,gfx_window,gfx_gc,x1,y1,x2,y2);
}

/* Change the current drawing color. */

void gfx_color( int r, int g, int b )
{
    XColor color;

    if(gfx_fast_color_mode) {
        /* If this is a truecolor display, we can just pick the color directly. */
        color.pixel = ((b&0xff) | ((g&0xff)<<8) | ((r&0xff)<<16) );
    } else {
        /* Otherwise, we have to allocate it from the colormap of the display. */
        color.pixel = 0;
        color.red = r<<8;
        color.green = g<<8;
        color.blue = b<<8;
        XAllocColor(gfx_display,gfx_colormap,&color);
    }

    XSetForeground(gfx_display, gfx_gc, color.pixel);
}

/* Clear the graphics window to the background color. */

void gfx_clear()
{
    XClearWindow(gfx_display,gfx_window);
}

/* Change the current background color. */

void gfx_clear_color( int r, int g, int b )
{
    XColor color;
    color.pixel = 0;
    color.red = r<<8;
    color.green = g<<8;
    color.blue = b<<8;
    XAllocColor(gfx_display,gfx_colormap,&color);

    XSetWindowAttributes attr;
    attr.background_pixel = color.pixel;
    XChangeWindowAttributes(gfx_display,gfx_window,CWBackPixel,&attr);
}

int gfx_event_waiting()
{
    XEvent event;

    gfx_flush();

    while (1) {
        if(XCheckMaskEvent(gfx_display,-1,&event)) {
            if(event.type==KeyPress) {
                XPutBackEvent(gfx_display,&event);
                return 1;
            } else if (event.type==ButtonPress) {
                XPutBackEvent(gfx_display,&event);
                return 1;
            } else {
                return 0;
            }
        } else {
            return 0;
        }
    }
}

/* Wait for the user to press a key or mouse button. */

char gfx_wait()
{
    XEvent event;

    gfx_flush();

    while(1) {
        XNextEvent(gfx_display,&event);

        if(event.type==KeyPress) {
            saved_xpos = event.xkey.x;
            saved_ypos = event.xkey.y;
            return XLookupKeysym(&event.xkey,0);
        } else if(event.type==ButtonPress) {
            saved_xpos = event.xkey.x;
            saved_ypos = event.xkey.y;
            return event.xbutton.button;
        }
    }
}

/* Return the X and Y coordinates of the last event. */

int gfx_xpos()
{
    return saved_xpos;
}

int gfx_ypos()
{
    return saved_ypos;
}

/* Flush all previous output to the window. */

void gfx_flush()
{
    XFlush(gfx_display);
}