[GRASSLIST:10435] Re: [GRASS5] gis manager 2 rc3 - bug fixes and updates

Glynn Clements glynn at gclements.plus.com
Mon Feb 20 12:27:40 EST 2006

Michael Barton wrote:

> As Glynn indicates, TclTk is very flexible in terms of user input options
> (mouse buttons, key combinations, etc.). If it becomes necessary to use a
> right mouse button (or mouse button-key combination) if needed to control a
> tool.
> However, the objective is to make the user access to GRASS's power as simple
> and straightforward as possible. That is, to get work done without having to
> think about how to work the program overly much. To this end, it is good to
> avoid non-standard input methods as much as possible and provide clear user
> feedback on tool operation--while still maintaining their function in an
> efficient manner.

One feature which I don't think that Tk provides is detecting key
press events for modifier keys themselves. This means that you can't
change the cursor depending upon the state of the modifier keys.

That's unfortunate; common behaviour of the zoom tool in paint
programs is click to zoom in, shift-click (or control-click or
alt-click) to zoom out, with the cursor having a +/- sign to indicate
the zoom direction based upon the modifier state. Whilst Tk lets you
determine the modifier state at the time of the click, you can't
determine it beforehand in order to reflect the state in the cursor.

This isn't critical; you can always provide help text in the status
bar or a tooltip to tell the user which modifier keys do what.

Glynn Clements <glynn at gclements.plus.com>

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