Search Top Index
HELP VEDNOTABS A. Sloman June 1991 (and VEDHARDTABS, VEDREADINTABS) <boolean> -> vednotabs <boolean> -> vedhardtabs <boolean> -> vedreadintabs CONTENTS - (Use <ENTER> g to access required sections) -- Introduction -- vednotabs -- vedhardtabs -- vedreadintabs -- Setting the value of vednotabs for each file -- See also: -- Introduction ------------------------------------------------------- The facilities described here enable users to control the way VED handles tab characters. (I.e. ascii 9). There are three main variables that are involved in determining whether tabs are preserved or deleted in files: vednotabs, vedhardtabs and vedreadintabs. The variable vedindentstep determines the spacing of "tab stops" in the file. -- vednotabs true ----------------------------------------------------- If VEDNOTABS is TRUE (default) then when an attempt is made to insert a tab character into the VED buffer (either via the keyboard, or via VED procedures such as * vedcharinsert and * vedinsertstring), then the tab is immediately converted into an appropriate number of spaces, up to the next tab column. The integer valued variable * VEDINDENTSTEP defines how far apart the 'tab' columns are in the file. Also, if VEDNOTABS is TRUE, then tabs are converted to spaces when the file is read in or written to disc. -- vednotabs false ---------------------------------------------------- If it is FALSE, then tabs are inserted when the TAB key is pressed, and tabs in files read from disc are preserved. The tabs are actually represented within the VED buffer as a number of tab characters corresponding to the number of screen locations filled by the tab, and this can sometimes cause confusion when user programs manipulate strings of text in VED's buffer. (See REF * veddecodetabs). -- vedhardtabs: controls insertion or deletion in a tab --------------- If VEDNOTABS is FALSE, i.e. if tabs are to be preserved, then it is ambiguous what should happen if you try to insert or delete a character in the middle of a tab. This ambiguity is resoved by VEDHARDTABS. If VEDHARDTABS is TRUE (the default) then if you try to insert or delete a character while the cursor is in the middle of the screen space corresponding to a tab, then the bell will ring, and the change will not be allowed. If VEDHARDTABS is FALSE, then the tab will be immediately converted to spaces and the appropriate insertion or deletion will be done without your noticing. If VEDNOTABS is TRUE, then VEDHARDTABS has no effect. -- vedreadintabs: controls preservation of tabs in disk files --------- Because many people wish to use VEDNOTABS set TRUE as their default, but wish to preserve tabs in files read from the disc, there is an additional variable, VEDREADINTABS, which if set TRUE, has the following effect: whenever a file is read in, if it contains any tabs, then the variable VEDNOTABS is set FALSE for that file, so that TABS are preserved. The default value of VEDREADINTABS is now TRUE, to minimise unwanted loss of tabs. Make it false in your vedinit.p file if you don't ever want to have tabs in files. -- Setting the value of vednotabs for each file ----------------------- Unlike the other variables, vednotabs is one of the variables associated with a file, which can be set differently for each file. For more information on such variables see REF * VEDVARS. It is possible to control the value of VEDNOTABS for individual files EITHER by redefining the procedure *VEDVEDDEFAULTS OR by setting up appropriate associations between different kinds of files and their VED variable settings, as described in HELP *VEDFILETYPES Note that the default value of the list -vedfiletypes- has an initial default condition that makes -vednotabs- true for all files. This can easily be overridden for certain files by adding an extra sublist. See HELP * VEDFILETYPES. -- See also: ---------------------------------------------------------- HELP * VEDINDENTSTEP - controlling the effect of tabs The following give information on setting VED defaults HELP * VEDFILETYPES HELP * VEDVEDDEFAULTS HELP * VEDINITIALISE (Changing state after file read in) HELP * INITIAL (Gives an overview of procedures for initialising your VED environment.) REF * vedinitialise For tailoring files on the basis of their contents. --- C.all/help/vednotabs --- Copyright University of Sussex 1991. All rights reserved. ----------