[Ipe-discuss] Ipe-discuss Digest, Vol 128, Issue 2

[Andrew Martchenko]

Terrific. Thanks very much for the undo code and for the bug report.
Once if fix the bugs and clean up the code a bit I'll add the ipelet to 
the wiki.

Cheers,
Andrew M.

On 03/07/16 20:00, ipe-discuss-request at lists.science.uu.nl wrote:
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>     1. Re: Tangent Lines (Otfried Cheong)
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> ----------------------------------------------------------------------
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> Message: 1
> Date: Sat, 02 Jul 2016 19:27:52 +0200
> From: Otfried Cheong <otfried at ipe.airpost.net>
> To: ipe-discuss at lists.science.uu.nl
> Subject: Re: [Ipe-discuss] Tangent Lines
> Message-ID:
> 	<1467480472.1835598.655081513.5C7109C2 at webmail.messagingengine.com>
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> On Sat, Jul 2, 2016, at 15:38, Andrew Martchenko wrote:
>> The ipelet works quite well, but I would like to improve it by having
>> some of the line segments be selected after the ipelet executes.
>> Specifically in my case, their can be up to four line segments that are
>> tangent to two circles (see attached pdf for example), the segments that
>> cross one another are rarely useful (to me) and I would like them to be
>> selected so that I can easily delete all such segments with a click of a
>> button. Is this something that can be done with an ipelet??
> Yes, this can be done, but it's a bit more tricky.
>
> An ipelet is not allowed to simply modify the current page - it must
> cooperate with Ipe's undo mechanism.   One way to do this is to call
> model:creation, as you do - this will create an entry for the undo stack
> that inserts one new object.   You call this several times, which means
> that if you try to undo your ipelet's effect, you'll see that you need
> to press Ctrl+Z several times to remove the tangents one by one.
>
> I'm attaching a modified version that has a new function create_objects
> that shows how to create an undo item for several new objects.   It
> selects only the ones that have the "select" attribute set.
>
> By the way, there seems to be a problem when you make two disks with the
> same radius and centers at equal y-coordinate:  the outer tangents are
> wrong.
>
> Cheers,
>   Otfried
>
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> End of Ipe-discuss Digest, Vol 128, Issue 2
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