Re: [Matplotlib-users] Feature request: automatic scaling of subplots, margins, etc

[todd r. <tod...@gm...>]

On Wed, May 11, 2011 at 1:59 PM, Benjamin Root <ben...@ou...> wrote:
>
>
> On Wed, May 11, 2011 at 12:47 PM, Brendan Barnwell <bre...@br...>
> wrote:
>>        One thing I've always wondered: is it fundamentally impossible to
>> change the fact that, in matplotlib, you cannot know how big a drawn
>> object will be until you actually draw it?  When I was doing some
>> animation stuff a while back this caused me a lot of headache, for the
>> reasons Tony Yu mentioned: it means you have to draw everything
>> multiple times.  It would really help if it were possible to specify
>> objects' parameters and get their sizes without drawing them.
>>
>> -- Brendan Barnwell
>> "Do not follow where the path may lead. Go, instead, where there is no
>> path, and leave a trail." --author unknown
>>
>
> Most things, we do know the sizes of.  It is my understanding that it is the
> text objects that is the unknown.  If this could be solved, then a layout
> engine would be much more feasible.  The problem is that even LaTeX has to
> re-render things multiple times to get this right for an arbitrary font.  If
> we were to restrict ourselves to particular fonts and package those fonts
> with matplotlib, then we could have an internal table of size information
> for each glyph and compute it on the fly and lay everything out right.  But,
> that would cause us to give up significant benefits for another benefit.
>
> I think the pain of the bootstrapping/re-rendering approach could be reduced
> significantly if we could get various aspects of matplotlib figure building
> to be faster.  Last time I checked, there is significant amount of
> processing time spent in calculating the ticks for the axes.  Maybe if we
> focus some efforts in improving the efficiency of certain parts of
> matplotlib, maybe we could introduce a convenience function like the one
> earlier in this thread that some users can choose to use with only a slight
> penalty in speed.  I personally would not want to make it default, but
> certainly would consider highly advertising such a function.
>
> Just my two cents,
> Ben Root

Perhaps there could be three options:

1. Manual mode: current behavior
2. Database mode: uses a list of known fonts.  When a font not found
in the database is used, it falls back to manual mode.
3. Automatic mode: uses a list of known fonts.  When a font not found
in the database is used, it renders the text alone in an invisible
figure to calculate the space needed, then uses that information to
set the margins.  Alternatively, create a temporary mini font database
just for the characters needed.  The former approach may be faster,
but the latter may be easier to program since it could share a lot of
code with the database.

There could also be a function to scan a particular font and add to
the database (there would probably be a separate user database in your
matplotlib configuration directory that this would use, as well as
probably caching the measurements from text used in automatic mode for
future versions of the figure).

-Todd