[Xastir-Dev] Map Drawing Tweaks

[Chris Bell]

> > This is an excellent idea, and it would go well with the suggestion I
> > made of providing minimum zoom levels for maps as part of the chooser.
> 
> Since we really need to get on to Xastir-2 sometime soon and not get
> bogged down in too much other stuff, how about this as a compromise:
> 

I think it is worth experimenting with these concepts, and how users
will interact and use them.  We should see what is cool and what is a
pain so our design spec for V2 is that much better focused.

> 
> Don't draw a map if its extents are less than 10% of the viewport in
> either direction.
> 
> Don't draw a map if the viewport is less than 10% of the map extents
> in both directions.

I experimented with this a while back for rasters, skipping maps that
were "too far" from 1:1 pixel translations.  It was hard to tune the
limits to get consistently good looking maps.  Basing the check on the
extents might not work in some cases (compare a 320x320 jpg vs. a
world shapefile) so it almost has to be per map.  Rasters are easy,
since they have an inherent pixel scale that we can check.  Vectors
are harder, how do you decide (other that the easy case of less that
xx% of the viewport) on the feature size?  I like to have my world
outline shapefile even when looking at close in details.  

> 
> Make the percent value user-changeable.
> 
> 
> Doing it this way instead of adding min/max to the Map
> Chooser->Properties menu would allow a quick fix, without having to
> implement a more complicated method twice, once for Xastir-1.2.x,
> once for Xastir-2/Database version.
> 
> It also allows the user to set a global default, avoiding going into
> the properties menu and changing things on every file.
> 

Maybe a global per type (vector/raster) as a better compromise?  I
found 3 was a reasonable raster limit (draw between 3:1 and 1:3 pixel
scales).  I still have that patch saved away somewhere, so would be
easy to add back in.   

btw, great suggestions!  This has been on my personal annoyance list
forever!  

Chris.
KD6ZWR
cbell at junknet.com