[reportlab-users] Writing a platypus DocTemplate that will fit all flowables on a single page

[Robin Becker]

Peter Russell wrote:

> Hi

> 

> I have an application where I need to be sure that user content all fits

> on a single page in two equally sized columns.  To do this I may need to

> shrink the font size of flowables, after they have been constructed, and

> passed to the build method of the DocTemplate.

> 

> Is this sort of thing possible, or will I need to use lower level

> constructs to achieve this?

> 

> Also I don't suppose anyone knows of a good algorithm for distributing

> blocks between two columns such that the two columns have equal height?

> 


get all of the relevant flowables in a list. Find their heights using the wrap 
method with an infinite height. You'll need to account for the inter flowable 
spaces eg space before space after etc. That gives you a good start point.

The _listWrapOn function in flowables.py does this for you. The KeepInframe 
flowable (in the same file) does the shrink trick for a single frame. The 
complexity there should give you an idea of what you're up against. When shrink 
is operative the wrap method is searching for a scaling that allows the given 
list of flowables to fit into the remaining space of the current frame. It does 
this by solving for a scaling that will make things fit.

Suppose you misuse KeepInFrame by providing it with an empty frame that's twice 
as long as your two frames and just as wide. The scaling that allows your 
flowables to fit should be near the required scaling for your pair of frames.

The hard part would be instrumenting that algorithm to provide you with the 
split point. Do you want to allocate only whole flowables to each frame or can 
the split. If you can do the split then a pair of KeepInFrames will now satisfy. 
Provided the split is fairly equal the final scalings should be close.
-- 
Robin Becker