[Qt-interest] Text Layout woes

[Josiah Bryan]

Jason H wrote:
> Can I please 'bump' this. I've been on the IRC channel, QtCentre, and no one seems to know...
> Thanks!

Jason -

I know the feeling - seems everyone else gets answers on theses lists 
sometimes except for you, eh? :-) Anyway...

I'm not sure if this is what you're trying to do or not - but I had a 
similar situation: I wanted to draw a QTextDocument, text wrapped to a 
rectangle, with a custom pen and brush. But there's no way to spec a 
custom pen and brush (that I know of) unless you paint the text document 
yourself. And when you paint the doc yourself, you dont get the word 
wrapping implicit in QTextLayout and friends. (At least, that's what 
I've experienced - maybe someone can correct me - please? :-)

Anyway, my solution was to write my own text wrapping function for a 
QTextDocument and layout the text myself. Source available on Google 
Code. Link to google code's online subversion repo, right to the start 
of the function in the source:

http://code.google.com/p/dviz/source/browse/trunk/src/items/TextBoxContent.cpp?spec=svn43&r=43#607

To see it in action, just checkout the trunk:

svn checkout http://dviz.googlecode.com/svn/trunk/ dviz-read-only

And do:
qmake
make
./dviz

By the way, I *gladly* welcome ANY improvements or fixes to that text 
layout function - please let me know if you fix anything in it. The only 
outstanding "bug" it has right now is that it doesn't adjust the 
baseline properly for fonts with widely varying heights in the same 
line. (E.g. a tall font and a short font on the same line - the tall 
font will be aligned with the top of the short font, sinking below the 
baseline. Anyway, thats to-be-fixed "sometime" - I welcome any help.)

To reuse, grab the updateTextConstraints() function and the 
TextLineSpecs class def from TextBoxContent.h and the hack to fit your 
needs. Should be fairly easy to adapt. (Oh, see the paint method just 
above the updateTextConstraints() for the actual painting of the text. 
Note that it draws the text using a QPainterPath, which is automatically 
created by TextLineSpec in it's constructor.)

Hope this helps.

Cheers!
-josiah

> ----- Original Message ----
> From: Jason H <scorp1us at yahoo.com>
> To: qt-interest at trolltech.com
> Sent: Wednesday, September 16, 2009 11:57:00 PM
> Subject: [Qt-interest] Text Layout woes
> 
> Hi I am tring to make an Affine Text Item for QGraphicsView.
> 
> 
> First, I rendered a single line of text with addText in a QPainterPath. My goal was to render a paragraph of text. QPainterPath doesn't do that. (Issue#1)
> 
> Then I ditched that and just used drawText from QPainter. But I found there were pixel differences. Whereas the path version scales smoothly, the raw painter does not. (Issue #2) 
> 
> So then I figured I'd use QTextLayout, and I come to find that QTextLine doesn't actually give you the text that will fit. (Issue #3) If it did, I could use the line's coords and text with QPainterPath to make my paragraph. 
> 
> Issue #4, is that I can't just create a QPainter for my QPainterPath and do my operations on the painter, and get back a QPainterPath. 
> 
> I just want a long line of affine text to be wrapped within a given rect. It seems that we must use QPainterPaths (because of issue #2) in the implementation.
> 
> So what is a boy to do?
> 
> 
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-- 

-=-=-=-=-=-=-=-=-=-=-=-=-
Josiah Bryan
Productive Concepts, Inc.
jbryan at pciint.com
(765) 964-6009, ext. 224