[Qgis-developer] Multicolumn legends in print composer

[Mathieu Pellerin]

Radim,

Following up on your implementation of the nice legend's multicolumn
feature. I've noticed two regression (one of which I've filed a bug
already).

1) The right-side box spacing is now miscalculated as it fails to add the
icon label space value. Issue 7099 (http://hub.qgis.org/issues/7099) has
been filed with more details and a accompanying screenshot.

2) There also was a regression in the way vertical spacing is calculate
between layer items and layers. An old issue, 3605, highlighted a similar
visual problem which was fixed in revision 08c88575 (
http://hub.qgis.org/projects/quantum-gis/repository/revisions/08c885759bd280339605ea07a221ab20f7dfdb75/diff/).
Long story short, layers with no titles are often used as part of a group
of layer items. As such, the solution found in the cited revision was to
take into account the layer item vertical spacing to the layer vertical
spacing. The multicolumn appear to have regressed this. I can open an issue
with screenshots if necessary.

Mathieu


On Sun, Nov 18, 2012 at 12:10 AM, Radim Blazek <radim.blazek at gmail.com>wrote:

> On Wed, Nov 14, 2012 at 11:11 AM, Andreas Neumann <a.neumann at carto.net>
> wrote:
> > Hi,
> >
> > Thanks to Radim we now have multi-column legends in print composer.
>
> Thanks to Régis and Agence de l'eau Adour as it was already mentioned by
> others.
>
> > This
> > was one of my long-time feature requests - but it never got to the top
> > of my requests so that we could pay for the work.
> >
> > Generally it works great, but I noticed two strange behaviors:
> >
> > * when having only one column (default) - the background rectangle is
> > way too small, not covering the full bouding box of the legend
>
> Width? Fixed.
>
> > * when going beyong 4 columns, QGIS gets really slow, hangs or crashes.
>
> Splitting of layers into columns is not that easy as it seems to be.
> It is a special sort of bin packing problem (NP-hard). Maybe it has
> its own name? I have used brute force because:
>  - I thought that the number of layer will never be too big
>  - implementaion of heuristic algorithm for such a marginal feature
> seemed to be overkill
>  - suboptimal solution could look quite bad
>
> You proved immediately that I was wrong. How many layers do you have?
> 70 I have read somewhere? My original idea was to calculate number of
> possibilities first and decide if heuristic should be used. Now it
> seems a necessity.
>
> Maybe I am wrong and there is a simple solution? Well, I did not know
> at the beginning that I am going to solve combinatorial exercises.
>
> Regarding the crash, I was quite careful, using value() where there
> was minimum suspicion that it could run out of range. Many
> combinations should not mean allocation of a lot of memory, just more
> computational time. Only one combination is always evaluated at time.
> Does it seem to be a memory allocation problem or out of list bounds?
> Could you send me backtrace off list?
>
> Please follow/comment http://hub.qgis.org/issues/1841
>
> Radim
>
> > Did other test the new multicolumn legends?
> >
> > Thanks Radim for your work!
> >
> > Andreas
> > _______________________________________________
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