1Fun Day11/21/20072Opening Discussion■Let's look at solutions to the interclass problem.■Vote was 7 for ASCII, 10 for X11.■Do you have any questions about the assignment?3Full Terminal Control■The ncurses library provides you with functions that allow you to write any ASCII character that you want to any point on the screen.■This can allow you to do ASCII animations.■It also includes functions for doing non-blocking input and input of non-character keys.■Normal scanf and getchar functions only read from a terminal once enter has been pressed.■Note that this isn't portable code. It won't work on a Windows box unless perhaps you have something like Cygwin.4Setup■In order to set up a window so that you can use curses function with it you need to initialize it.■You do this with the WINDOW *initscr() function. Let's look at the man page for this function.■The WINDOW* that is returned needs to be remembered because it has to be passed to most of the functions that will draw out characters for us.5“Drawing” Functions■There are number of different functions that can output to the screen. I'm not going to type them all up here, but I'll give a little list. We can look at a web page for a more complete list.mvaddch(win,y,x,ch)mvwaddstr(win,y,x,str)mvwaddchstr(win,y,x,chstr)■After calling one of these call refresh(win) to see the change.■You can use the See Also section of the man pages to find more related functions.6Input Functions■There are a number of functions for getting input in curses. The simplest is wgetch(win).■Unless you set other options this will work just like getchar() blocking the program and printing to screen.■The following lines will allow non-blocking, non-printed input that doesn't print.keypad(win,1);wtimeout(win,0);necho();7X-Windows and X11■Linux and Unix boxes use a windowing system called X-windows. This is a very general graphical system that allows a lot of flexibility.■One of the most significant features of X-windows is the ability to display windows remotely.■Cygwin can give you X-windows under Windows, but by default you can't use it there.8Windows■There are several steps in getting an X window.Get a display. (XOpenDisplay)Get a screen number on the display. (XDefaultScreen)Create the window. (XCreateSimpleWindow)■Here again, the man pages can help us get more information.9Events■Most GUI environments use events for user input. That's because you can't block the thread and there are many different event types (key presses, mouse actions, exposures, etc.)■The is a big union called XEvent that has the different events. Every structure in it shares certain elements at the beginning.■The XNextEvent function will return the next event to you. You switch on the type of the event to determine what you should do about it.■For X-programs the event handling likely belongs in a loop.10Exposures■One type of event that is particular to the X system is exposures.■They tell you that some part of the window has been exposed and that you need to redraw it.■By default, X-windows don't remember what is drawn in them so the refresh has to be done manually.11Graphics Context■The graphics context in X is a struct that tells X how to draw things.■You can create multiple instances of this structure and set them up to draw in different ways. You can think of each one as being like a pencil or brush with a different color, width, etc.■The struct is called XGCValues.12Drawing and Colors■There are a bunch of drawing functions in X11 that begin with XDraw and XFill. They are fairly simply to master and running a command like “man -k XDraw” will list them.■Colors are more challenging. The XAllocNamedColor will give you a color from a set of “named” colors. For more variety you need to use XCreateColormap to make a full color map. This makes X applications more cross-platform compatible, but harder to work with.13Minute Essay■What are you doing for Thanksgiving?■Interclass Problem – Write a little program to use one of these two
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