[josm-dev] make slippy map a core feature

[Dave Hansen]

On Sun, 2009-10-11 at 23:05 +0200, Sebastian Klein wrote:
> Dave Hansen wrote:
>  > Have you tried a recent version?  For me, it is the single fastest way
>  > to browse the slippymap.  It's way faster and more responsive than any
>  > browser.  It also has features that allow you to tune the quantity of
>  > tiles that it keeps in memory.  It's not a direct size limit, but it
>  > should let you have control. 
>  >
> 
> Yes, I have the recent version.
> After making myself familiar with it a little more I have to admit it's 
> not that bad. :)
> 
> These are the problems I encountered:
> 
>  * When a new area is loaded the entire map is colored red (with some 
> strange stripes at the border). Then after 10 seconds, it says 'pending 
> download', and at least the data layer is now visible. After further 4 
> second the first tiles are shown. The CPU is at 100% for this time.
>   In contrast to that, the download dialog shows the tiles with no 
> delay. Furthermore, without the plugin, the data layer is shown immediately.

This is strange.  I really don't see any of this behavior.  Can you send
me th preferences that you have set for the slippy map plugin?  What
projection are you using?

The CPU is probably pegged because the internal image loaders inside of
the java implementation are constantly trying to make new images
available a new bits are received.  It is usually resizing them, too.

>  * Moving the map is quite sluggish.

Again, I don't know what to say other than that this works fine for me.
It could use some improvement for sure.

>  * For many zoom levels the text is somehow blurred and sometimes not 
> readable. This is because the images need to be resized to the given 
> zoom level. I don't know how to avoid this, maybe some fine tuning could 
> improve the situation.

The plugin makes an effort to
1. Download the best looking tile that it can for the area which is
   being viewed
2. Show other data for that area if the best data is unavailable (being
   downloaded)

The plugin changes the zoom level of the tiles based on when pixels in
the tiles are being squished or stretched a certain amount.

>  >>> Too decrease the network traffic one would then need a disk cache, but
>  >>> make the tiles expire after approx. one hour and on demand.
>  >> ... and *not* change zoom levels automatically ;-)
>  >
>  > I thought this was already a feature, but I'd be happy to go back and
>  > revisit it.  To me, it doesn't make a lot of sense to do this.  How do
>  > you use it that this is important?
>  >
> 
> One could add a checkbox to the right click menu of the layer, that 
> allows to turn off autozoom. I don't see how this would be particularly 
> useful, but why not...

Yup, that's a good suggestion.

> Frederik Ramm wrote:
>  > Why do you want to work with it at all? [...] Plus, the slippy map 
> tiles are so colorful that it is difficult to read anything drawn on top 
> of that.
>  >
> 
> I would use it to review my gps traces. This can be done by some other 
> application (i. e. prune), as well. But as I have to load it in JOSM 
> anyway, it would be nice to have slippy map background.
> 
> Additionally, if there was an advanced disk tile cache, one could easyly 
> load the tiles of the holiday region at home and then use it offline.
> 
> If friends ask you to show them the traces, and then you have a black 
> area with some dots, it's not very impressive. :)

I'd rather not implement a disk cache from scratch.  Does anybody have
good suggestions on code to steal for this?

-- Dave