[reportlab-users] mixing flowables and exact placement in a platypus doc

[Andy Robinson]

will at phototropia.org wrote:
> Friends:
>      If I have a platypus doc with flowables(paragraphs,tables etc), and I
> want to mix in pages with exact placement drawings,text etc where no
> flowables with the wrap property, I see two ways to do it:
> 1)Define a page template with all of my exact placement
> stuff(text,drawings) without frames, and change to that page template when
> I want to use it, and then change back to a page template with frames for
> flowables.
> 2)Think of a frame as kind of bounding box.  Use drawings and text as
> flowables as recommended in the userguide, but calculate the size,
> position and padding of the frame so that the flowed drawing/object ends
> up exactly on the page where you would have placed it by just stating x,y
> coordinates.
> 
> I am leaning towards 1, but am I missing something here?

Possibly missing some documentation we should have written ;-)
In Report Markup Language we 'switch modes' all the time, but there are 
high level tags to make it obvious.  Here's some of the underlying 
techniques:

(1)If you're in flowing mode, and you want a rectangular box to draw on, 
you can create a special flowable and put your drawing code in it, just 
implementing the draw method below.   Your graphics will appear relative 
to the current rendering position (i.e. between the paragraph above and 
below).


class Illustration(Flowable):
     def __init__(self, width, height):
         self.width = width
         self.height = height
     def wrap(self, *args):
         return (self.width, self.height)
     def draw(self):
	#my graphics code here....

You are also free to lie about the size and 'draw outside the box', eg. 
to make hanging side headings in the margin.

(2) Drawings (the chart classes in reportlab/graphics) work like this too

(3) There are lots of events in BaseDocTemplate for you to override 
which can let you draw explicitly when you start/finish a page, a frame 
and so on.  These would let you draw in absolute page coordinates

(4) when drawing directly, you can easily instantiate any flowable 
object and call
	thing.drawOn(canvas, x, y),
provided you call
    	thing.wrap(height, width)
first to tell it the available size.  If it's a fixed size just pass the 
any old size to wrap(...).

(5) when drawing directly, you can also create a Frame object and add 
flowable objects to it.   I'd do this if I was rendering some 
lines-and-boxes thing like an invoice where I am highly likely to be in 
charge of the page breaks, but wanted a few paragraphs of text for the 
small print.

I hope this gives you a few ideas.  If not, a concrete example of what 
you're trying to render would be helpful and I can suggest more specific 
strategies.

Good luck,


Andy