How To Setup Keymapping In gschem

Stefan Petersen, spe@geda.seul.org
This document is released under GPL (http://www.fsf.org/copyleft/gpl.html)

1999-07-24






About this document

The purpose of this document is to try to explain how key mapping works in gEDA/gschem schematic entry program. It uses the langauge Scheme a lot, which is a Lisp-dialect and is used in gschem as a scripting language. If you're not familiar with this language, please see the dictionary (see appendix A, page X, for a short description of common data structures used in Scheme.

1   Functionality

When you press a button in gschem, a Scheme function is called. This function (press-key) accepts one argument, the name of the pressed key. Then there are Scheme routines to evaluate which key you pressed and call the appropriate action.

Since the evaluation routines are written in Scheme it's simple to change the behaviour of what happens when you presses a key. You can implement macros or do several things at each key press. For example, the ``repeat-last-key´´ command is implemented completly in Scheme.

2   Keymaps

The current implementation is built-up around ``keymaps''. A keymap is a list with pairs. Each pairs first element (the car-element) is which key to react on, and the second element (cdr) is a ``what-to-do-next''. This can either be an action, a function to call or another keymap.

2.1   An example on keymaps

Two simple examples of keymaps is seen in figure 1 and figure 2.


(define global-keymap
  '(("Escape" . cancel)
    ("a" . add-keymap)))
Figure 1: First example of an simple keymap

In figure 1 is the keymap called global-keymap. This keymap is the first keymap used. If you for example press the 'a'-key, global-keymap tells us that next key pressed will be interpreted by add-keymap (see figure 2).


(define add-keymap
  '(("c" . add-component)
    ("a" . add-attribute)
    ("n" . add-net-hotkey)))
Figure 2: Second example of an simple keymap

If you, after you pressed 'a', press a 'c' the built-in action add-component comes to live. This is exactly what had happend if you had selected Add, Component...in the menubar.

When an action has been performed the current keymap is reset back to
global-keymap.

Available built-in actions are listed in appendix B.

2.2   Description of keys

The key are described as:

For a -- ``a''
For Shift-A -- ``Shift A''
For Control-a -- ``Control a''
For Alt-a -- ``Alt a''

There are a few simple rules to follow when keys for a new keymap is defined:

2.3   Actions

The built-in actions that can be called are listed in appendix B.

Sometimes you may notice that there are similar actions, like edit-rotate-90 and edit-rotate-90-hotkey. They do the same thing, just that the -hotkey actions is run immediately, while the other wait for you to select something.

2.4   Function calls

If the cdr-element is an ordinary Scheme function that function is called. The function can't receive any arguments.

This can be used if you want to do complex tasks, like several actions in a row or do some calculation. You can do rather advanced actions since the Guile dialect of Scheme used in gschem is extended from plain Scheme. For further information on Guile, please see the Guile documentation.

2.5   Another keymap

If the cdr-element is another keymap then that command is a multi-key command, ie you need to press at least two keys to cause an action. The first key is desribed in the first keymap, which points to the next keymap. The second keymap describes what should happen when the second key is pressed.

3   Where are the key mappings stored

The keymap is stored in the startup file for gschem, namely
<startpath, typically /usr/local>/share/gEDA/system-gschemrc.

You can then redefine or add keymaps as you like (I think) in your local setup file for gschem,
~/.gEDA/gschemrc

The Scheme functions used to resolve keypresses to actions are stored at
<startpath, typically /usr/local>/share/gEDA/scheme/gschem.scm.
This is configurable in the gschemrc files.

A   Dictionary

function A subprogram in Scheme, C or other programming languages.
action What gschem (in this case) does when you press a key or a set of keys.
list A data structure very common in Lisp-looking languages like Scheme. Simply put, a long list of values.
pair (also dotted pair) A datstructure also very common in Lisp-looking languages.
car element First element in a pair. Since lists are decendents from pairs, car is also the first element in a list.
cdr element (pronounced cudr) The second element in a pair. In the list case it denotes the rest of list.

B   Built-in actions in gschem

Run
grep gh_register_procedure_0_0 gschem/src/g_register.c
and do some work in emacsen.

file-new-window
file-new
file-open
file-script
file-save
file-save-as
file-save-all
file-print
file-image
file-close-window
file-quit
edit-select
edit-copy
edit-copy-hotkey
edit-move
edit-move-hotkey
edit-delete
edit-rotate-90
edit-rotate-90-hotkey
edit-mirror
edit-mirror-hotkey
edit-slot
edit-color
edit-edit
edit-lock
edit-unlock
edit-translate
edit-embed
edit-unembed
edit-hidden
view-redraw
view-zoom-full
view-zoom-limits
view-zoom-in
view-zoom-out
view-zoom-box
view-zoom-box-hotkey
view-pan
view-pan-hotkey
view-update-nets
page-manager
page-next
page-prev
page-new
page-close
page-discard
page-print
add-component
add-attribute
add-net
add-net-hotkey
add-text
add-line
add-line-hotkey
add-box
add-box-hotkey
add-circle
add-circle-hotkey
add-arc
add-arc-hotkey
add-pin
add-pin-hotkey
hierarchy-open-symbol
attributes-attach
attributes-detach
attributes-show-name
attributes-show-value
attributes-show-both
attributes-visibility-toggle
options-text-size
options-snap-size
options-action-feedback
options-grid
options-snap
options-show-log-window
options-show-coord-window
misc-misc
cancel

This document was translated from LATEX by HEVEA.