Re: [Xournal-devel] xournal with search and jump to next/previous annotation

[Denis A. <au...@ma...>]

Hi Daniel,

In the canvas coordinate system, the origin is the top-left-most point 
of the document, and the rectangle occupied by a given page has 
upper-left corner at (page->hoffset, page->voffset) and lower right 
corner at (page->hoffset + page->width, page->voffset + page->height).
(the Y axis increases downwards; the units are points (1/72 in)).

In the PDF coordinate system, the origin is usually at the lower-left 
corner of the page, but there can be exceptions. I haven't been able to 
find any way in the poppler API to get the bounding box of the page, 
only its size, so either there's a missing piece of the API, or poppler 
always converts things so the lower-left corner is (0,0). Who knows. The 
Y axis increases going upwards; the units are points (1/72 in), however 
the page may be scaled differently in the xournal document since one can 
change the paper size.

With this understood, let's say that you have gotten the page size from 
poppler by something like
poppler_page_get_size(pdfpage, &pdfwidth, &pdfheight);
Then a point with coordinates (x,y) in the PDF system translates to the 
point with coordinates

(page->hoffset + x*page->width/pdfwidth,
  page->voffset + page->height - y*page->height/pdfheight)

in the canvas. This is again assuming the page does start at (0,0), but 
unless you see a way to get the page's cropbox in the poppler API, 
that'll have to be the standing assumption (it only fails for a few 
specific documents, 2005 US federal tax forms being one notable example; 
and perhaps poppler always brings back the corner to (0,0) anyway).

Denis


On 12/14/2009 03:12 AM, D M German wrote:
>
>
> Hi everybody,
>
> as I mentioned before, I have been trying to implement search. So far I
> have the interface for the search box done, and very rudimentary search
> support (xournal will jump to the next page where the string appears).
>
> There are several tasks that need to be done, but perhaps the most
> important is to highlight the search result.
>
> I am not a very good UI programmer, but if somebody can help me figure
> out how to determine the canvas coordinates to use (i.e. help me use the
> PDF coordinates to draw the box around the text) I can continue
> improving the search backend.
>
> Because my current development version of xournal has several UI patches
> applied, it has been difficult to create a patch (due to glade generated
> code). For that reason I am creating a bare git repo with my changes. It
> might be useful to those who want to track my changes, or help:
>
>
> http://github.com/dmgerman/xournal
>
>
> thanks in advance,
>


-- 
Denis Auroux                    au...@ma...
MIT Department of Mathematics   ON LEAVE AT UC BERKELEY
77 Massachusetts Ave. 2-236
Cambridge MA 02139