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This is a description of how to actually use the screen package. In it, we assume all updating, reading, etc. is applied to All instructions will work on any window, with changing the function name and parameters as mentioned above. In order to use the screen package, the routines must know about terminal character- istics, and the space for and must be allocated. These functions are performed by Since it must allocate space for the windows, it can overflow core when attempting to do so. On this rather rare occasion, returns ERR. must be called before any of the routines which affect windows are used. If it is not, the program will core dump as soon as either or are referenced. However, it is usually best to wait to call it until after you are sure you will need it, like after checking for startup errors. Terminal status changing routines like and should be called after Now that the screen windows have been allocated, you can set them up for the run. If you want to, say, allow the window to scroll, use If you want the cursor to be left after the last change, use If this isn't done, will move the cursor to the window's current after updating it. New windows of your own can be created, too, by us- ing the functions and will allow you to get rid of old windows. If you wish to change the official size of the terminal by hand, just set the variables and to be what you want, and then call This is best done before, but can be done either before or after, the first call to as it will always delete any existing and/or before creating new ones. Now that we have set things up, we will want to actually update the terminal. The basic functions used to change what will go on a window are and adds a character at the current , returning ERR if it would cause the window to illegally scroll, printing a character in the lower right-hand corner of a terminal which automatically scrolls if scrolling is not allowed. changes the current to whatever you want them to be. It returns ERR if you try to move off the window when scrolling is not allowed. As mentioned above, you can combine the two into to do both things in one fell swoop. The other out- put functions, such as and all call to add characters to the win- dow. After you have put on the window what you want there, when you want the portion of the terminal covered by the window to be made to look like it, you must call In order to optimize finding changes, assumes that any part of the window not changed since the last of that window has not been changed on the terminal, that you have not refreshed a portion of the terminal with an overlapping window. If this is not the case, the routines and are provided to make it look like a desired part of window has been changed, thus forcing check that whole subsection of the terminal for changes. If you call with it will make the screen look like thinks it looks like. This is useful for implementing a command which would redraw the screen in case it get messed up. Input is essentially a mirror image of output. The complementary function to is which, if echo is set, will call to echo the char- acter. Since the screen package needs to know what is on the terminal at all times, if characters are to be echoed, the tty must be in raw or cbreak mode. If it is not, sets it to be cbreak, and then reads in the character. All sorts of fun func- tions exists for maintaining and changing information about the windows. For the most part, the descriptions in section 5.4. should suffice. In order to do certain optimizations, and, on some terminals, to work at all, some things must be done before the screen routines start up. These functions are performed in and which are called by In order to clean up after the routines, the routine is provided. It restores tty modes to what they were when was first called. Thus, anytime after the call to initscr, should be called before exiting.
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