by: Stefan Petersen, spe@geda.seul.org This document is released under GPL
1999-07-24
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.
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.
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.
Two simple examples of keymaps are 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.
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:
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.
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.
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.
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.
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. |
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