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From: Kai-Martin Knaak <knaak AT iqo DOT uni-hannover DOT de>
Subject: Re: [geda-user] how to you actually draw a polygon?
Date: Mon, 07 Mar 2016 20:02:34 +0100
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Peter Clifton wrote:

> On 6 Mar 2016 16:20, "Kai-Martin Knaak"
> <kmk AT familieknaak DOT de> wrote:
> 
>> A combination of 45° and 90° lines should always be able to close the
>> polygon.
> 
> This is true, but given a fine grid, it isn't always easy to get the
> vertices to line up as you might want to achieve that.

I imagined, the GUI does the hard work of finding a combination that fits. 
The resulting 45° corner may not be on grid. But we tend to do this for 
tracks too (when they snap to off grid pins).


>> In a perfect GUI the cursor would snap to the start vertex.
> 
> Not enough, unless we added some means to create two edge segments at
> once (like with tracking).... 

The two-edge segment strategy used for routing is what had in mind. 
Wouldn't it be possible to reuse this algorithm for polygon creation?

Maybe, the similarity to routing can be exploited even more: 

1) draw the first segment

2) create two point like helper pin objects. One at each end of the first 
segment.

3) create a net that connects the two helper pins.

4) Flag the first segment to not be ignored by the update rats action.

5) Draw the polygon like you do with regular routing

Benefits: The application and the user already know what it takes to 
satisfy an unrouted net. All the bells and whistles of regular routing are 
available. You could even use the autorouter to close the last gap.

---<)kaimartin(>---
-- 
Kai-Martin Knaak                                  tel: +49-511-762-2895
Universität Hannover, Inst. für Quantenoptik      fax: +49-511-762-2211	
Welfengarten 1, 30167 Hannover           http://www.iqo.uni-hannover.de
GPG key:    http://pgp.mit.edu:11371/pks/lookup?search=Knaak+kmk&op=get