Drawing on Windows VS GTK2 (Linux)
lazarus / 39-Graphics

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groundcad · 2015-09-01 13:55

Hi
I developed a 2D CAD software (http://www.groundcad.com/) using
lazarus 1.4.2
I am using LCL only. The version 0.3.1 is stable on windows 32 xp/7
with no problems in the drawing.
Actually, I ported my software to linux(32) mint 17.2. and I used
Lazarus 1.4.2 configured on GTK2.
On linux If I zoomed In (+) my drawing, I get a duplicated lines in my
canavs !
What is the problem in gtk2 ?

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marcov · 2015-09-01 14:25

Do you only draw in the paint event? That is the most common failure
with non windows widgetsets.

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groundcad · 2015-09-01 14:36

thank you Markov for your replay
I used  paintbmp  : Bitmap ;
            paintbox   : TPaintbox;

I draw in the canvas of paintbmp

I refresh The painbox by the procedure

procedure Tmainform.paintboxPaint(Sender: TObject);
begin
  paintbox.Canvas.Draw(0,0,paintbmp);
end;

Can you explain to me where is problem in gtk2 or qt4(not tested) ?

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derek.john.evans · 2015-09-01 16:21

Quote from: marcov on September 01, 2015, 04:25:48 pmDo you only draw
in the paint event? That is the most common failure with non windows
widgetsets.

I think what marcov is asking, is, are you triggering a refresh using
paintboxPaint(paintbox) or are you calling paintbox.invalidate;

*EDIT* BTW. Ya, CAD looks really cool.

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groundcad · 2015-09-01 17:37

Yes I call the procedure paintboxPaint(sender) after the drawing in
the canvas of my bmp also I test using paintbox.Invalidate same
problem.

In windows,I dont have a problem ,  if i zoom In or zoom out my
drawing.

But in linux 32 (mint 17.2) with lazarus 1.4.2 configured on gtk2.
I have a duplicated entities in my drawing, if I make a maximum zoom.

I check my code many times ?

show the picture.

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zamtmn · 2015-09-01 17:43

I understand nothing. Please give a screenshot of how it should look
right, and how it looks wrong. Also, make a minimum code of the
problem, but the working and compiled

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groundcad · 2015-09-01 17:57

In my software I used 
            paintbmp  : Bitmap ;
            paintbox   : TPaintbox;

 I draw in the canvas of paintbmp.
 I refresh The painbox by the procedure
 procedure Tmainform.paintboxPaint(Sender: TObject);
 begin
   paintbox.Canvas.Draw(0,0,paintbmp);
 end;

In Windows 32  xp / 7  (Lazarus 1.4.2), I dont have a problem

In Linux 32 mint 17.2 (Lazarus 1.4.2 with GTK2 ) , When I make a
maximum zoom in (+) in, I get a duplicated entities in my drawing, 
Why ?

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derek.john.evans · 2015-09-01 18:31

Mmmm, looks like integer overflow. (or, at least beyond the range
provide by GTK)

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zamtmn · 2015-09-01 20:07

I tried groundcad on GTK. Yes, it is similar to overflow. Primitives
are not duplicated, it is other primitives, that should not be
visible. Look at the screenshot, the blue line must stay somewhere far
to the right, and should not be visible. Check the formulas by which
you believe zoom.
Generally you need to do check visible primitives and draw only what
is visible. This will help to avoid this and greatly accelerate your
program

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groundcad · 2015-09-01 20:34

Thank you Mr Zamtmn
Before the drawing,  I will check if an entity is inside the screen.

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zamtmn · 2015-09-02 08:52

You're welcome. Need more CAD programs in FPC\Lazarus, great and
diverse