Xlib Fundamentals the concept of windows in X

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Xlib Fundamentals

the concept of windows in X

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Windows in X X Window Programming Lab

Xlib Fundamentals

Xlib is a set of library routines used to implement the basic X calls.

X toolkits not only provide all the functionality of Xlib routines and is much easier to use.

It is still important to understand how the Xlib works.

- Creating and displaying the window - Drawing with X

- Text - Color - Events

J. Park 1/11 CSE 180 (U Penn)

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Windows are what X is all about

Each window is a data structure stored in the X server.

Identied by an ID of Window type (usually an unsigned 32 bit integer).

To create a single window application 1. Connect to the server

2. Check the environment 3. Create the window

4. Display the window

| !!!! |

N. Destroy window and close the display

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Connecting to the server and Checking the environment

Make the initial connection: XOpenDisplay()

Display *display;

display = XOpenDisplay ( (char *) NULL);

Determine which screen you are connected to: DefaultScreen()

int screen;

screen = DefaultScreen(display);

Ask the X server what the characteristics of the screen are:

DisplayWidth (display,screen) DisplayHeight (display,screen) DefaultDepth (display,screen)

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Creating the window

XCreateSimpleWindow(), XCreateWindow()

#include <X11/Xlib.h>

Display *display;

Window parent_window;

int x, y;

unsigned int width, height;

unsigned int border_width;

int depth;

unsigned int class;

Visual *visual;

unsigned long valuemask;

XSetWindowAttributes *attributes;

window = XCreateWindow (display, parent_window, x, y, width, height, border_width, depth, class, valuemask, attributes );

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XCreateWindow()

Returns the widow ID

parameters:

{

target display

{

parent's id

{

desired pixel location of the TLC of this new window

{

size of the window in pixels

{

how wide the window's border should be (in pixels)

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{

number of bit planes available

{

class: InputOutput, InputOnly or CopyFromParent

{

The attributes structure contains 15 elds related to the window. The valuemask variable is a bit mask, indicating which of the 15 elds you have actually specied.

background pixel - the color of the window background

border pixel - the color of the window border

event mask - ask for window expose events

override redirect - allows you to override the window manager

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#include <X11/Xlib.h>

#include <X11/Xutil.h>

Display *display;

int screen;

XSetWindowAttributes attributes;

unsigned long attr_mask;

attributes.background_pixel = WhitePixel(display, screen);

attributes.border_pixel = BlackPixel(display, screen);

attributes.event_mask = ExposureMask;

attributes.override_redirect = False;

attr_mask = CWBackPixel | CWBorderPixel | CWEventMask | CWOverrideRedirect;

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Getting ready to display the window

Before we can display the window we need to provide some hints about it to the window manager: data structure

XSize- Hints

{

As with XSetAttributes, there is a mask, this time stored inside the structure in the eld ags (e.g.,

USPosition - user specied x, y

USSize - user specied width, height PPosition - program specied position PSize - program specied size

PMinSize - min size PMaxSize - max size

PAspect - min and max aspect ratios)

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Once the size hints have been set up they are passed to thewindow manager using the

XSetNormalHints

^function.

Display * display;

Window window;

XSizeHints hints;

XSetNormalHints(display, window, &hints);

Initialize the window's name (before we actually display the window) to be shown in the windows title bar:

XStoreName

function

Display * display;

Window window;

char window_name [ ];

XStoreName (display, window, window_name);

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Displaying the window

XMapWindow(), XMapRaised()

Display * display;

Window window;

XMapWindow(display,window);

XMapRaised(display,window);

To be sure that the window is displayed we must ush the cache.

XFlush(display);

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Cleaning up

Once our program has nished we should destroy all windows and close the display.

XDestroyWindow(display, window);

XCloseDisplay(display);