[Qgis-developer] arrows on line strings?

Magnus Homann magnus at homann.se
Thu Jan 31 18:06:13 EST 2008

Tim Sutton wrote:
> Hi Stefanie
> Its been requested a few times but thus far no one has had time to
> implement it. To add it would require adding a bit of logic in
> qgsvectorlayer to overdraw an arrow onto a line once it has been
> renderered (Qt doesnt provide any flow style line styles). Magnus
> Homann has just done similar work for point symbols. If you would like
> to do this work yourself it would be most welcome and we can certainly
> try to help as needed. Others may be interested to help so do let us
> know if you plan to start such work - it will also help to prevent
> duplication of effort.
> Best regards
> Tim
> 2008/1/31, Stefanie Tellex <stefie10 at media.mit.edu>:
>> Hi,
>> I would like to draw arrows on line strings, since they represent
>> movement vectors and I want to show the direction of movement.  I
>> couldn't find any way to do that in the gui or any obvious way in the
>> programmatic API.  What's the best way to add this feature or is it
>> there already somewhere?

I had a vague idea to redo the rendering logic to make it more 
pluggable, so that it would be easier to write your own renderers. I 
also had a an idea to write a vector renderer, which wouldn't be very 
hard at all. But right now, I think we should wait for the render 
mechanism to improve.

We also ahve to do some benchmarking and speed optimization on rendering.

Magnus Homann

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