[reportlab-users] Absolute coordinates of rendered flowables?

[Dinu Gherman]

Robin Becker:


> Dinu flowable drawOn methods are the ones that are passed the x, y.

>

> f.drawOn(canvas,x,y,_sW)

>

> _sW is supposed to be the spare width available for purposes of  

> horizontal adjustment ie available - flowable width.

>

> Unfortunately the generic version Flowable.drawOn also handles the  

> adjustment of x according to the flowable's hAlign attribute so by  

> the time the f._drawOn method gets called the translation to x',y  

> may have already occurred.

>

> However, the translation is the very last thing done prior to  

> _drawOn being called. So the very last thing on the code stack looks  

> like 'a b c d e f cm' where a b c d e f are numeric values  

> representing the latest transformation. If canvas.py has  

> ENABLE_TRACKING = 1 (which is the default) then canv._currentMatrix  

> should hold our estimate of the canvas transformation. Since the  

> flowable will be 'drawn' at 0,0 in the that frame of reference you  

> should be able to use the inverse transformation to map 0, 0 back to  

> the 'absolute' position.


I know about drawOn methods, but I'm not sure if they solve my problem.
What want to do is use flowables like the following, which draw some-
thing at absolute coordinates on the page while not consuming any space
in the story themselves:

class AbsoluteRect(Flowable):
     """A rectangle  given in absolute canvas coordinates.

     Use in a Platypus story like this: AbsoluteRect((x, y, w, h))
     (This is mostly like XBox, but with absolute coordinates.)
     """

     def __init__(self, rect):
         Flowable.__init__(self)
         self.width = 0
         self.height = 0
         self.rect = rect

     def __repr__(self):
         return "AbsoluteRect(x=%s, y=%s, w=%s, h=%s)" % self.rect

     def draw(self):
         x, y, w, h = self.rect
         self.canv.rect(x, y, w, h)
         self.canv.line(x, y, x+w, y+h)
         self.canv.line(x, y+h, x+w, y)

Regards,

Dinu