Re: Many changes in layers and markers

[Robert Park <rbpark exolucere ca>]

On Wed, Feb 9, 2011 at 2:46 PM, Jiří Techet <techet gmail com> wrote:
> I have finally finished the major changes I wanted to get into 0.10
> (see the code in our git). Sorry for the delay. In the end there were
> more API changes I originally planned - because the existing programs
> will have to be updated anyway, I thought it would be better to make
> all the cleanups in one release rather than during several releases. I
> hope that the current architecture is flexible enough that no other
> major changes will be needed in future releases.

I hadn't seen a commit since early January and I was starting to worry
that libchamplain was dead... nice to see all this work done all of a
sudden, it's like Christmas all over again ;-)

Also, my app hasn't been subject to any API breakage in like two
months, so this'll be fun.

> * The license and the scale actors have been separated from
> ChamplainView.

Excellent! A while back I had asked for a coordinate display feature
and you told me that this was a prerequisite to adding such a feature,
so I'm glad to see this step in the right direction.

> ChamplainBaseMarker -> ChamplainMarker
> ChamplainMarker -> ChamplainLabel
> ChamplainPoint - it is now a circular marker that can be inserted into a layer
> ChamplainCustomMarker - a marker that implements ClutterContainer -
> use instead of adding ClutterActors into ChamplainMarker
> ChamplainPolygon -> ChamplainMarkerLayer (also the name _polygon_ was
> changed to _path_ which is more descriptive in my opinion)
> ChamplainLayer -> ChamplainMarkerLayer

I like the idea of renaming 'polygon' into 'path' because that is a
much less technical name (and more indicative of it's use), but I'm
not sure about the name 'ChamplainMarkerLayer'. The name doesn't make
it obvious that that's what you need to use when you want to draw
squiggles on the map. Perhaps it should be called
ChamplainDrawingLayer? That seems like a more general name that would
indicate it's used for drawing points or polygons.

> champlain_view_get_coords_at() -> champlain_view_x_to_longitude() and
> champlain_view_y_to_latitude() to get the latitude and longitude from
> x, y

If these two methods return only a float with no success boolean, then
that totally obviates the need for those python overrides I wrote.
Excellent!

> So far I have concentrated on interfaces mostly and the implementation
> itself definitely deserves some more work:
>
> * fix #638652 - this is my top priority bug now.

Dear god *yes*. THANK YOU.

> I know that chaning the API of a library is a good way to be hated, on

Hahaha. Yeah.

> the other hand the changes will make the architecture much more
> flexible and maintainable. For instance, ChamplainView doesn't have to
> care about markers and polygons which was the case previously (1200
> LOC less in ChamplainView).

Excellent work my friend!

> It only knows about the inserted
> Champlainlayers and its the responsibility of the layers to perform
> the necessary actions. If you want to create your special layer or
> marker, no problem - no change in ChamplainView is needed and you can
> do whatever you wish.

Cool. So what would be the recommended way to go about implementing a
custom widget on the map that's pinned to the view, but not the map?

> This is a good time to tell me:
> 1. If something is missing in the new marker API so it can be added
> 2. Something should be renamed
> 3. If you think that the change of the API is totally stupid
> All kinds of feedback are welcome.

I'll begin porting my app over the next couple days and let you know
what I think of the changes.

> For people who wish to test the new features and don't have GTK3
> installed yet, I have prepared a patch (see the attachment) which
> makes libchamplain compile under GTK2. The launcher-gtk demo now
> contains movable markers connected with a polygon line so you can test
> how it's updated when dragged.

That sounds like it would be fun to play with. I'm definitely
interested in this draggable interface, it would be very useful to my
app as users are allowed to manually position photos. Currently they
do this by moving the map view, and then there's a button to move the
selected images into the map center. Being able to drag the markers
directly into position would certainly be a nice UI improvement.

Thanks for all your hard work!


-- 
http://exolucere.ca