added doublebuffer examples

x/button.cpp

 /*
 CS 349 Code Examples: X Windows and XLib
 
-    animation.cpp   Ball bouncing in xinfo.window (minimal version)
+    button.cpp   Implement a ToggleButton UI Widget
 
 - - - - - - - - - - - - - - - - - - - - - -
 

x/doublebuffer.cpp → x/doublebuffer1.cpp

 /*
 CS 349 Code Examples: X Windows and XLib
 
-    doublebuffer.cpp   How to do double buffering (minimal version)
-    				   Note, it's pretty hard to see any difference.
+    doublebuffer1.cpp   How to do double buffering (minimal version using animation.cpp)
+    				    Note, it's pretty hard to see any difference.
 
 - - - - - - - - - - - - - - - - - - - - - -
 

x/doublebuffer2.cpp

+/*
+CS 349 Code Examples: X Windows and XLib
+
+    doublebuffer2.cpp   Adds many balls to animation to make doublebuffering
+    					effect more obvious.
+
+- - - - - - - - - - - - - - - - - - - - - -
+
+See associated makefile for compiling instructions
+
+*/
+
+#include <cstdlib>
+#include <iostream>
+#include <unistd.h>
+#include <sys/time.h>
+
+#include <X11/Xlib.h>
+#include <X11/Xutil.h>
+
+#include <vector>
+
+
+// get microseconds
+unsigned long now() {
+	timeval tv;
+	gettimeofday(&tv, NULL);
+	return tv.tv_sec * 1000000 + tv.tv_usec;
+}
+
+
+using namespace std;
+
+Display* display;
+Window window;
+
+// frames per second to run animation loop
+int FPS = 60;
+
+int main( int argc, char *argv[] ) {
+	display = XOpenDisplay("");
+	if (display == NULL) exit (-1);
+	int screennum = DefaultScreen(display);
+	long background = WhitePixel(display, screennum);
+	long foreground = BlackPixel(display, screennum);
+	window = XCreateSimpleWindow(display, DefaultRootWindow(display),
+	                             10, 10, 300, 200, 2, foreground, background);
+	XSelectInput(display, window,
+	             ButtonPressMask | KeyPressMask); // select events
+	XMapRaised(display, window);
+	XFlush(display);
+
+	XEvent event; // save the event here
+
+	// ball postition, size, and velocity
+	vector<XPoint> ballPos;
+	vector<XPoint> ballDir;
+	int numBalls = 1000;
+
+	for (int i = 0; i < numBalls; i++) {
+		XPoint bp;
+		bp.x = rand() % 300;
+		bp.y = rand() % 200;
+		XPoint bd;
+		bd.x = rand() % 3;
+		bd.y = rand() % 3;
+		ballPos.push_back(bp);
+		ballDir.push_back(bd);
+	}
+
+	// XPoint ballPos;
+	// ballPos.x = 50;
+	// ballPos.y = 50;
+	int ballSize = 10;
+	// XPoint ballDir;
+	// ballDir.x = 3;
+	// ballDir.y = 3;
+
+	// create gc for drawing
+	GC gc = XCreateGC(display, window, 0, 0);
+
+
+	// time of last window paint
+	unsigned long lastRepaint = 0;
+
+	XWindowAttributes w;
+	XGetWindowAttributes(display, window, &w);
+
+	// DOUBLE BUFFER
+	// create bimap (pximap) to us a other buffer
+	int depth = DefaultDepth(display, DefaultScreen(display));
+	Pixmap	buffer = XCreatePixmap(display, window, w.width, w.height, depth);
+
+	bool useBuffer = true;
+
+	// event loop
+	while ( true ) {
+
+		// TRY THIS
+		// comment out this conditional to see what happens when
+		// events block (run the program and keep pressing the mouse)
+		if (XPending(display) > 0) {
+			XNextEvent( display, &event );
+
+			switch ( event.type ) {
+
+			// mouse button press
+			case ButtonPress:
+				useBuffer = !useBuffer;
+				cout << "double buffer " << useBuffer << endl;
+				break;
+
+			case KeyPress: // any keypress
+				KeySym key;
+				char text[10];
+				int i = XLookupString( (XKeyEvent*)&event, text, 10, &key, 0 );
+				if ( i == 1 && text[0] == 'q' ) {
+					XCloseDisplay(display);
+					exit(0);
+				}
+				break;
+			}
+		}
+
+		unsigned long end = now();
+
+		if (end - lastRepaint > 1000000 / FPS) {
+
+			Pixmap pixmap;
+
+			if (useBuffer) {
+
+				pixmap = buffer;
+				// draw into the buffer
+				// note that a window and a pixmap are “drawables”
+				XSetForeground(display, gc, WhitePixel(display, DefaultScreen(display)));
+				XFillRectangle(display, pixmap, gc,
+				               0, 0, w.width, w.height);
+			} else {
+				pixmap = window;
+				// clear background
+				XClearWindow(display, pixmap);
+			}
+
+
+			for (int i = 0; i < numBalls; i++) {
+
+
+				// draw ball from centre
+				XSetForeground(display, gc, BlackPixel(display, DefaultScreen(display)));
+				XFillArc(display, pixmap, gc,
+				         ballPos[i].x - ballSize / 2,
+				         ballPos[i].y - ballSize / 2,
+				         ballSize, ballSize,
+				         0, 360 * 64);
+
+				// update ball position
+				ballPos[i].x += ballDir[i].x;
+				ballPos[i].y += ballDir[i].y;
+
+				// bounce ball
+				if (ballPos[i].x + ballSize / 2 > w.width ||
+				        ballPos[i].x - ballSize / 2 < 0)
+					ballDir[i].x = -ballDir[i].x;
+				if (ballPos[i].y + ballSize / 2 > w.height ||
+				        ballPos[i].y - ballSize / 2 < 0)
+					ballDir[i].y = -ballDir[i].y;
+			}
+
+			// copy buffer to window
+			if (useBuffer) {
+				XCopyArea(display, pixmap, window, gc,
+				          0, 0, w.width, w.height,  // region of pixmap to copy
+				          0, 0); // position to put top left corner of pixmap in window
+			}
+
+			XFlush( display );
+
+			lastRepaint = now(); // remember when the paint happened
+		}
+
+		// IMPORTANT: sleep for a bit to let other processes work
+		if (XPending(display) == 0) {
+			usleep(1000000 / FPS - (end - lastRepaint));
+		}
+
+
+	}
+	XCloseDisplay(display);
+}