Why DrawText output is different on Bitmap.Canvas and Form.Canvas?
lazarus / 39-Graphics

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Yurii · 2013-04-27 09:17

Why DrawText output is different on Bitmap.Canvas and Form.Canvas for
strings which combine arabic and other symbols? (See attachment)
What can I do to fix that?

...
  DrawText(Form1.Canvas.Handle, PChar(s), Length(s), R, DT_WORDBREAK);
  DrawText(Bitmap.Canvas.Handle, PChar(s), Length(s), R,
DT_WORDBREAK);
  Form1.Canvas.Draw (10, 40, Bitmap);
...

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Blaazen · 2013-04-27 09:59

So this is about Themes and Qt4, yes?
I'm not sure, I don't use RightToLeft and I cannot test. I guess
Canvas.TextStyle can affect it.
Try:
Code: [Select]with Bitmap.Canvas.TextStyle do RightToLeft:=True;
EDIT: Better (cross-platform) solution:
Code: [Select]with Bitmap.Canvas.TextStyle do
RightToLeft:=Application.IsRightToLeft;

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Yurii · 2013-04-27 15:17

Using Canvas.TextStyle is the same as using DT_RTLREADING flag.
Code: [Select]DrawText(Form1.Canvas.Handle, PChar(s), Length(s), R,
DT_WORDBREAK or DT_RTLREADING);
  DrawText(Bitmap.Canvas.Handle, PChar(s), Length(s), R, DT_WORDBREAK
or DT_RTLREADING);
Both don't change anything.

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Blaazen · 2013-04-27 16:09

Sorry, the code above does not work (it is packed record).
Try this:
Code: [Select]var aTS: TTextStyle;
begin
  aTS.RightToLeft:=True;
  Canvas.TextStyle:=aTS;

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Yurii · 2013-04-27 16:51

Nothing changed again.
In Windows many strings  like this ':مایع تحقیق' are shown in a proper
way, but not this
Code: [Select]s := '% ,خطأ نسبي';
Strings like this 'Pa ,تنش' are shown in a proper way both in Linux
and Windows.
When I faced this problem for the first time I prepared two Persian
language files for Linux and for Windows. But in Linux I couldn't use
the same strings for translation data input forms and result
presentation. I think that creation of different strings for this
purpos is not right.

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zeljko · 2013-06-14 10:38

Quote from: Yurii on April 27, 2013, 11:17:24 amWhy DrawText output is
different on Bitmap.Canvas and Form.Canvas for strings which combine
arabic and other symbols? (See attachment)
What can I do to fix that?

...
  DrawText(Form1.Canvas.Handle, PChar(s), Length(s), R, DT_WORDBREAK);
  DrawText(Bitmap.Canvas.Handle, PChar(s), Length(s), R,
DT_WORDBREAK);
  Form1.Canvas.Draw (10, 40, Bitmap);
...

http://bugs.freepascal.org/view.php?id=24340  and issue is resolved.
Note that it'll work correct only with Qt libs >= 4.7 (I've tested
with qt 4.7.4 and 4.8.3(4))