CLIM mail archive
Re: "Grouping" of presentations
Date: Thu, 21 May 1992 16:24 MEST
From: Jeff Morrill <jmorrill%BBN.COM@fhg.de>
Date: Wed, 20 May 1992 15:05+0200
From: Stefan Bernemann <email@example.com>
Subject: "Grouping" of presentations
this time :-) I want to implement a feature of drawing applications or
graph editors, namely the grouping of presentations. That means, I want
to *replace* a set of presentations (no matter of what type) by ONE
other presentation (e.g. of type "group").
This is rather easy to do using incremental redisplay. I have something
like this for displaying tree-structured groupings. A non-terminal node
in the tree has a "display children" bit that is either on or off. The
display method on a node checks the bit and recurses if indicated.
However, I don't want to erase and readraw any graphical output done to
the screen, for efficienc reasons but mostly to minimize unnecessary
That's exactly what the :cache-value option to updating-output is for.
Sorry, I wasn't specific enough. The forming of groups, i.e. determining
which objects (presentations) belong to one group, is done by the user.
There is no a priori group structure. Consider the following example:
| A B |
| C |
This shows (phantasy required!) a window with presentations A, B and C.
Now the user selects presentations A and C and wants them to be ONE
GROUP - that means, the presentations must be replaced by one
presentation of type group or such:
| ___ |
| |A |B |
| | | |
| | C| |
| --- |
However, I don't want A and B do be *redrawn*. I don't see how I can use
incremental redisplay for this - I think I have to manipulate the output
history, but don't know how.
Mail: Stefan Bernemann ! Phone: +49-231-9743-139
c/o FhG IML Dortmund ! Fax: +49-231-9743-234
Emil-Figge-Str. 75 ! Email: firstname.lastname@example.org
D-4600 Dortmund 50, FRG !
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