[reportlab-users] Styling within platypus flowables

[Robin Becker]

On 13/02/2014 10:38, Nick Moffitt wrote:

> Given that we're now clearer on what sort of page layout I'm describing,

> is there any advice on how best to handle this sort of layout with

> platypus?  Or should I just stick to writing to the canvas directly, and

> do my own reflowing and line/page breaking by hand?

.......

I don't think paragraphs are going to be much use to you directly. Conceivably a 
pre-processor could detect the [X] tags and convert them in to so-called 
callback definitions which are inserted into the text of a normal paragraph.

Swing [D]low, sweet [G]chari[D]ot,

can be converted into

Swing <onDraw name="myDrawChord" label="D"/>low, sweet <onDraw 
name="myDrawChord" label="G"/>chari<onDraw name="myDrawChord" label="D"/>ot,


where drawChord has to be the name of a callable attribute on the canvas being 
used to render the paragraph. When platypus is rendering the paragraph and sees 
the representation of the <onDraw> tag it calls out to the callable thusly


tx._canvas._curr_tx_info=dict(tx=tx,cur_x=cur_x,cur_y=cur_y,leading=leading,xs=tx.XtraState)
func(tx._canvas,kind,cbDefn.label)


here tx is the textobject that's being used to render the para. So effectively 
the onDraw callable has to have a signature like this

def myDrawChord(canv,kind,label):
     '''
     canv is our canvas
     kind == 'onDraw'
     label = whatever label was set in the paragraph onDraw label attribute
     '''
     #extract positional information
     _curr_tx_info = canv._curr_tx_info
     tx = _curr_tx_info['tx']
     cur_x = _curr_tx_info['cur_x']
     cur_y = _curr_tx_info['cur_y']
     leading = _curr_tx_info['leading']
     xs = _curr_tx_info['xs']



     .....
     #do whatever you want in terms of drawing the marks etc etc


The XtraState thing xs has these elements

	xs.cur_y  at start of rendering (I think)
	xs.f      fragment
	xs.style  the style object we're using
	xs.lines
	xs.underlines list of underline positions
	xs.underlineColor
	xs.strikes list of strike positions
	xs.strikeColor
	xs.links list of link positions
	xs.link f.link
	xs.textColor
	xs.backColors list of backgrounds to be painted

for most purposes you should only need the cur_x/cur_y from the tx rendering 
info, _curr_tx_info. Then I guess you need to make the leading large enough to 
allow drawing of the label above or below the original text line.


I'm not sure exactly how the splitting will work with this scheme as our 
fragment algorithm is quite contorted about where it likes to split when these 
zero width (onDraw) items appear ie they're not transparent so far as the 
linebreaking algoritm is concerned.
-- 
Robin Becker