add examples for 1-3-windowing system

x/1-3-WindowingSystem/hello.cpp

+/*
+CS 349 Hello X Windows
+
+- - - - - - - - - - - - - - - - - - - - - -
+
+Commands to compile and run:
+
+    g++ -o drawing.min drawing.min.cpp -L/usr/X11R6/lib -lX11 -lstdc++
+    ./drawing.min
+
+Note: the -L option and -lstdc++ may not be needed on some machines.
+
+*/
+
+#include <unistd.h>
+#include <cstdlib>
+#include <iostream>
+#include <X11/Xlib.h>
+
+Display* display;
+Window window;
+
+int main( int argc, char* argv[] ) {
+
+  // open display
+  display = XOpenDisplay("");
+  if (!display) exit (-1);
+  int screen = DefaultScreen(display);
+  int w = 200;
+  int h = 100;
+  window = XCreateSimpleWindow(display, DefaultRootWindow(display),
+                               10, 10, w, h, 2,
+                               BlackPixel(display, screen), WhitePixel(display, screen));
+  XMapRaised(display, window);
+  XFlush(display);
+
+  // give server 10ms to get set up before sending drawing commands
+  usleep(10 * 1000);           
+
+  // drawing demo with graphics context here ...
+  GC gc = XCreateGC(display, window, 0, 0);       // create a graphics context
+  XSetForeground(display, gc, BlackPixel(display, screen));
+  XSetBackground(display, gc, WhitePixel(display, screen));
+
+  //load a larger font
+  XFontStruct * font;
+  font = XLoadQueryFont (display, "12x24");
+  XSetFont (display, gc, font->fid);
+
+  // draw text
+  std::string text("hello X Windows");
+  XDrawImageString( display, window, gc,
+                    10, h / 2, text.c_str(), text.length());
+
+  XFlush(display);
+  std::cout << "ENTER2exit"; std::cin.get(); // wait for input
+  XCloseDisplay(display);
+
+}

x/1-3-WindowingSystem/makefile

+# super simple makefile
+# call it using 'make NAME=name_of_code_file_without_extension'
+# (assumes a .cpp extension)
+NAME = "null.min"
+
+# Add $(MAC_OPT) to the compile line for macOS 
+# (should be ignored by Linux, set to nothing if causing problems)
+MAC_OPT = -I/opt/X11/include
+
+all:
+	@echo "Compiling..."
+	g++ -o $(NAME) $(NAME).cpp -L/opt/X11/lib -lX11 -lstdc++ $(MAC_OPT)
+
+run: all
+	@echo "Running..."
+	./$(NAME) 
+
+clean:
+	-rm *o

x/1-3-WindowingSystem/null.min.cpp

+/*
+CS 349 Code Examples: X Windows and XLib
+
+    null        Creates and destroys a display (a good first test to see
+                if X Windows is working).
+
+- - - - - - - - - - - - - - - - - - - - - -
+
+See associated makefile for compiling instructions
+
+*/
+
+#include <cstdlib>
+#include <iostream>
+#include <X11/Xlib.h> // main Xlib header
+
+Display* display;
+
+int main() {
+    display = XOpenDisplay(""); // open display (using DISPLAY env var)
+    if (display == NULL) {
+        std::cout << "error\n";
+        exit (-1);
+    } else {
+        std::cout << "success!: ";
+    	XCloseDisplay(display); // close display
+    }
+}

x/1-3-WindowingSystem/openwindow.cpp

+/*
+CS 349 Code Examples: X Windows and XLib
+
+    openwindow     Opens a single blank window
+
+- - - - - - - - - - - - - - - - - - - - - -
+
+See associated makefile for compiling instructions
+
+*/
+
+#include <cstdlib>
+#include <iostream>
+#include <list>
+
+/*
+ * Header files for X functions
+ */
+#include <X11/Xlib.h>
+#include <X11/Xutil.h>
+
+using namespace std;
+
+
+/*
+ * Information to draw on the window.
+ */
+struct XInfo {
+    Display*    display;
+    int      screen;
+    Window   window;
+};
+
+
+/*
+ * Function to put out a message on error exits.
+ */
+void error( string str ) {
+    cerr << str << endl;
+    exit(0);
+}
+
+
+/*
+ * Create a window
+ */
+void initX(int argc, char* argv[], XInfo& xinfo) {
+    XSizeHints hints;
+
+    hints.x = 100;
+    hints.y = 100;
+    hints.width = 400;
+    hints.height = 400;
+    hints.flags = PPosition | PSize;
+
+    /*
+    * Display opening uses the DISPLAY  environment variable.
+    * It can go wrong if DISPLAY isn't set, or you don't have permission.
+    */
+    xinfo.display = XOpenDisplay( "" );
+    if ( !xinfo.display )   {
+        error( "Can't open display." );
+    }
+
+    /*
+    * Find out some things about the display you're using.
+    */
+    // DefaultScreen is as macro to get default screen index
+    xinfo.screen = DefaultScreen( xinfo.display ); 
+
+
+
+    unsigned long white, black;
+    white = XWhitePixel( xinfo.display, xinfo.screen ); 
+    black = XBlackPixel( xinfo.display, xinfo.screen );
+
+    xinfo.window = XCreateSimpleWindow(
+        xinfo.display,              // display where window appears
+        DefaultRootWindow( xinfo.display ), // window's parent in window tree
+        hints.x, hints.y,           // upper left corner location
+        hints.width, hints.height,  // size of the window
+        10,                         // width of window's border
+        black,                      // window border colour
+        white );                        // window background colour
+
+    // extra window properties like a window title
+    XSetStandardProperties(
+        xinfo.display,      // display containing the window
+        xinfo.window,       // window whose properties are set
+        "x1_openWindow",    // window's title
+        "OW",               // icon's title
+        None,               // pixmap for the icon
+        argv, argc,         // applications command line args
+        &hints);            // size hints for the window
+
+    /*
+     * Put the window on the screen.
+     */
+    XMapRaised( xinfo.display, xinfo.window );
+
+    XFlush(xinfo.display);
+}
+
+
+int main ( int argc, char* argv[] ) {
+
+    XInfo xinfo;
+
+    initX(argc, argv, xinfo);
+
+    // wait for user input to quit (a concole event for now)
+    cout << "press ENTER to exit";
+    cin.get();
+
+    XCloseDisplay(xinfo.display);
+}

x/1-3-WindowingSystem/openwindow.min.cpp

+/*
+CS 349 Code Examples: X Windows and XLib
+
+    openwindow.min     Opens a single blank window.
+
+- - - - - - - - - - - - - - - - - - - - - -
+
+See associated makefile for compiling instructions
+
+*/
+
+#include <cstdlib>
+#include <iostream>
+#include <X11/Xlib.h>
+
+Display* display;
+Window window;                          // save the window id
+
+int main( int argc, char* argv[] ) {
+    display = XOpenDisplay("");         // open display using DISPLAY env var
+    if (!display) exit (-1);            // couldn't open, so bail
+    int screen = DefaultScreen(display);// info about the display
+    window = XCreateSimpleWindow(
+         display,                       // display where window appears
+         DefaultRootWindow(display),    // window's parent
+         10, 10,                        // location: x,y
+         400, 300,                      // size: width, height
+         2,                             // width of border
+         BlackPixel(display, screen),   // foreground colour
+         WhitePixel(display, screen));  // background colour
+    XMapRaised(display, window);        // put window on screen
+    XFlush(display);                    // flush the output buffer
+    std::cout << "ENTER2exit"; std::cin.get(); // wait for input
+    XCloseDisplay(display);
+}

x/readme.md

+# CS 349 X Windows and XLib Example Code
+
+
+To make ("compile and link") an example, use the included makefile with 
+the name of cpp file passed as a variable. For example, to make hello.cpp:
+
+```bash
+	make NAME="hello"
+```
+
+Then, to run:
+
+```bash
+    ./hello 
+```
+
+Or you can even compile, link, and run in one step:
+
+```bash
+    make run NAME="hello"
+```
+