316 lines
5.3 KiB
HTML
316 lines
5.3 KiB
HTML
<HTML
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><HEAD
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><TITLE
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>X</TITLE
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><META
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NAME="GENERATOR"
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CONTENT="Modular DocBook HTML Stylesheet Version 1.63
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"><LINK
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REL="HOME"
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TITLE="Linux Backspace/Delete mini-HOWTO"
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HREF="index.html"><LINK
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REL="PREVIOUS"
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TITLE="Why It Doesn't (Always) Work"
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HREF="why.html"><LINK
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REL="NEXT"
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TITLE="What You Should Do When Writing Applications"
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HREF="writing.html"></HEAD
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><BODY
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CLASS="SECT1"
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BGCOLOR="#FFFFFF"
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TEXT="#000000"
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LINK="#0000FF"
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VLINK="#840084"
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ALINK="#0000FF"
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><DIV
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CLASS="NAVHEADER"
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><TABLE
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WIDTH="100%"
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BORDER="0"
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CELLPADDING="0"
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CELLSPACING="0"
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><TR
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><TH
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COLSPAN="3"
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ALIGN="center"
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>Linux <B
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CLASS="KEYCAP"
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>Backspace</B
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>/<B
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CLASS="KEYCAP"
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>Delete</B
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> mini-HOWTO</TH
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></TR
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><TR
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><TD
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WIDTH="10%"
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ALIGN="left"
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VALIGN="bottom"
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><A
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HREF="why.html"
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>Prev</A
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></TD
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><TD
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WIDTH="80%"
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ALIGN="center"
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VALIGN="bottom"
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></TD
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><TD
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WIDTH="10%"
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ALIGN="right"
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VALIGN="bottom"
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><A
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HREF="writing.html"
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>Next</A
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></TD
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></TR
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></TABLE
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><HR
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ALIGN="LEFT"
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WIDTH="100%"></DIV
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><DIV
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CLASS="SECT1"
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><H1
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CLASS="SECT1"
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><A
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NAME="X"
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>4. X</A
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></H1
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><P
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>The situation under X is not really different. There is just a
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different layer, that is, the X window system translates the scancodes into
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its own keysyms, which are much more varied and precise than the console
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ones, and feeds them into applications (by the way, this is the reason why
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<SPAN
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CLASS="APPLICATION"
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>XEmacs</SPAN
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> is not plagued by the problem: X
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translates keycode 22 to keysym <SPAN
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CLASS="KEYSYM"
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>BackSpace</SPAN
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> and keycode 107
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to keysym <SPAN
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CLASS="KEYSYM"
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>Delete</SPAN
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>, and then the user can easily assign to
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those keysyms the desired behaviour). Of course, a terminal emulator
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program (usually a VT100 emulator in the X world) must translate the
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X keysyms into ASCII sequences, so we are again in our sore
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business.</P
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><P
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>More in detail, usually <SPAN
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CLASS="APPLICATION"
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>xterm</SPAN
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> behaves
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exactly like the console (i.e., it emits the same <SPAN
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CLASS="ACRONYM"
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>ASCII</SPAN
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>
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sequences), but, for instance, <SPAN
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CLASS="APPLICATION"
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>gnome-terminal</SPAN
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> in
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Red Hat <7.0 or ≥7.1 emits <SPAN
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CLASS="SYMBOL"
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>BS</SPAN
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> for
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<B
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CLASS="KEYCAP"
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>Backspace</B
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> and <SPAN
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CLASS="SYMBOL"
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>DEL</SPAN
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> for
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<B
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CLASS="KEYCAP"
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>Delete</B
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>. The real fun starts when you realise that by
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default they use the <EM
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>same</EM
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> terminal-database entry, so
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the fact that the <TT
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CLASS="LITERAL"
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>kbs</TT
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> capability is associated to an
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<SPAN
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CLASS="ACRONYM"
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>ASCII</SPAN
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> <SPAN
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CLASS="SYMBOL"
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>DEL</SPAN
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> makes all correctly behaving
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applications produce the same behaviour for the <B
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CLASS="KEYCAP"
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>Backspace</B
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>
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and <B
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CLASS="KEYCAP"
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>Delete</B
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> keys in
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<SPAN
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CLASS="APPLICATION"
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>gnome-terminal</SPAN
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>. The simple statement
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<TABLE
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BORDER="1"
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BGCOLOR="#E0E0E0"
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WIDTH="100%"
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><TR
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><TD
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><FONT
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COLOR="#000000"
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><PRE
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CLASS="SCREEN"
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> bash$ export TERM=gnome</PRE
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></FONT
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></TD
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></TR
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></TABLE
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> can solve the problem in this case for
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correctly behaving applications. Well, not always, because your system
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could lack an entry in the terminal database named
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<TT
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CLASS="LITERAL"
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>gnome</TT
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>, in particular if it is not very up-to-date.</P
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><P
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>In any case, this is not always a solution: if, for instance, you
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have a Red Hat 7.0 distribution, your
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<SPAN
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CLASS="APPLICATION"
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>gnome-terminal</SPAN
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> behaves like a console. But
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beware: if you upgraded your desktop using the Helix distribution, then
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your <SPAN
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CLASS="APPLICATION"
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>gnome-terminal</SPAN
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> behaves like a pre-7.0 Red
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Hat.</P
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><P
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>Just to make easier the following discussion, let us define
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<I
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CLASS="FIRSTTERM"
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>standard</I
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> a VT100 emulator behaving like the console,
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and <I
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CLASS="FIRSTTERM"
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>deviant</I
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> one that emits <SPAN
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CLASS="SYMBOL"
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>BS</SPAN
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> for
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<B
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CLASS="KEYCAP"
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>Backspace</B
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> and <SPAN
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CLASS="SYMBOL"
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>DEL</SPAN
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> for
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<B
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CLASS="KEYCAP"
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>Delete</B
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>.<A
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NAME="AEN188"
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HREF="#FTN.AEN188"
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>[1]</A
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>
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Thus, for instance, <SPAN
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CLASS="APPLICATION"
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>xterm</SPAN
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> has always been
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standard in the Debian distribution, while it switched a couple of times
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from standard to deviant and viceversa in Red Hat; the behaviour of
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<SPAN
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CLASS="APPLICATION"
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>gnome-terminal</SPAN
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> is even more erratic. See <A
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HREF="morehack.html"
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>Section 8</A
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> for some information on how to turn a deviant terminal
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into a standard one.</P
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></DIV
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><H3
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CLASS="FOOTNOTES"
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>Notes</H3
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><TABLE
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BORDER="0"
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CLASS="FOOTNOTES"
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WIDTH="100%"
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><TR
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><TD
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ALIGN="LEFT"
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VALIGN="TOP"
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WIDTH="5%"
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><A
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NAME="FTN.AEN188"
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HREF="x.html#AEN188"
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>[1]</A
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></TD
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><TD
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ALIGN="LEFT"
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VALIGN="TOP"
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WIDTH="95%"
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><P
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>Also these definitions have been
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asserted/disputed several times commenting this document. If you have any
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definitive information on this subject, please write me.</P
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></TD
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></TR
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></TABLE
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><DIV
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CLASS="NAVFOOTER"
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><HR
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ALIGN="LEFT"
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WIDTH="100%"><TABLE
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WIDTH="100%"
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BORDER="0"
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CELLPADDING="0"
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CELLSPACING="0"
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><TR
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><TD
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WIDTH="33%"
|
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ALIGN="left"
|
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VALIGN="top"
|
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><A
|
|
HREF="why.html"
|
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>Prev</A
|
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></TD
|
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><TD
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WIDTH="34%"
|
|
ALIGN="center"
|
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VALIGN="top"
|
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><A
|
|
HREF="index.html"
|
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>Home</A
|
|
></TD
|
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><TD
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WIDTH="33%"
|
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ALIGN="right"
|
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VALIGN="top"
|
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><A
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HREF="writing.html"
|
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>Next</A
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></TD
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></TR
|
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><TR
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><TD
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WIDTH="33%"
|
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ALIGN="left"
|
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VALIGN="top"
|
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>Why It Doesn't (Always) Work</TD
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><TD
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WIDTH="34%"
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ALIGN="center"
|
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VALIGN="top"
|
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> </TD
|
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><TD
|
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WIDTH="33%"
|
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ALIGN="right"
|
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VALIGN="top"
|
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>What You Should Do When Writing Applications</TD
|
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></TR
|
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></TABLE
|
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></DIV
|
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></BODY
|
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></HTML
|
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> |