scale painter to fit my widget

[jesse_mark]

hello ,

Im trying to paint a rect in paintEven,
but the rect I draw has a definided values for hieght and widt, which could be really big comparing to the widget.

so i want to painter

- to scale the rect based on the widget size, how can i do that ??
- as well as i want my (0,0) to be in the bottom left of the widget not in the top left.

I have attache an example of what i have trying to and the result i got.

i also tried to do zooming and panning on it.

Thanks for any help

here an example of the code im doing :
PaintEventTest.zip

[wysota]

Have a look at QPainter::setWindow() and QPainter::setViewport().

[jesse_mark]

by looking into setWindow and setViewPort,

I understood that by setWindow i can tell the painter the rect i want it to draw in it.
so i did this :

QRect widgetRect = this->rect();
QRect windowRect; 
 
windowRect.setHeight(widgetRect.height()-50);
windowRect.setWidth(widgetRect.width()-50);
windowRect.setX(widgetRect.x()-50);
windowRect.setY(widgetRect.y()-50); 
 
 painter.setWindow(windowRect); 
painter.drawRect(myRect);

QRect widgetRect = this->rect();
QRect windowRect; 

windowRect.setHeight(widgetRect.height()-50);
windowRect.setWidth(widgetRect.width()-50);
windowRect.setX(widgetRect.x()-50);
windowRect.setY(widgetRect.y()-50); 

 painter.setWindow(windowRect); 
painter.drawRect(myRect);

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expecting that when i draw using the painter it will draw inside this windowRect.

but it does not, it will draw out of the border in the invisable area for the user.

I dont know what exactlly i should set it.

[wysota]

setWindow() defines a logical rectangle the painter will use when accepting coordinates from you. setViewport() defines a physical rectangle the logical rectangle will be mapped to. So if you pass setViewport(widget->rect()) and say... setWindow(QRect(0,0,100,50)) then 100 will be scaled to the width of your widget and 50 to the height of your widget.

[jesse_mark]

Thanks , this is what i was looking for.
but now im facing other problem, which is the size.

for example,

I want to draw an ellipce in the same area.

i want the postion of the ellipce to be affected and to be mapped to viewport area. but i want it to keep the same size i assinge to it.

for example :

Painter.drawEllpice(x,y,2,2);
now when i map it to the viewPort, and when the x,y are really big, you can not see the ellipce at all and as size is mapped as well and beome sooo small.

so is there a way to can keep the size always the same no matter what x,y is or no matter what viewport i gave.

Thanks

[wysota]

Did you use setWindow?

[jesse_mark]

yes I did.

this is wat i did:
Qrect my rect(x,y,h,w);
QPoint p(x1,y1);

painter.setViewPort(widget->rect());
painter.setwindow(x,y,h,w);


painter.drawRect(myrect);
painter.drawEllipce(p,2,2);


is my rect is small , the ellipce is fine, but if the rect is big and then the ellipce is sooo samll that u cannot see
i have to set the size of the ellipce so big so i can see it.

like:
painter.drawEllipce(p,2000,2000);

but ofcource then is the window is small the ellipce will be too big.

[wysota]

What did you pass as x, y, h and w? (btw. it is w and h and not h and w)

[jesse_mark]

i passed the value of my rect:

for example :

QRect myrect(0,0,2000,4000);
QPoint(1000,2000);
 
QRect veiwRect = widget->rect();
 
 
painter.setViewPort(viewRect)
painter.setWindow(myRect);
 
painter.drawRect(myRect);

QRect myrect(0,0,2000,4000);
QPoint(1000,2000);

QRect veiwRect = widget->rect();


painter.setViewPort(viewRect)
painter.setWindow(myRect);

painter.drawRect(myRect);

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I notice something else is that, it will fill the whole widget and it will not use its a coordinates, so even if was the height a way bigger than the width,
it still show that the width bigger than the height.

[wysota]

If you pass such big values then no wonder your ellipse is so small. 2 / 2000 = 0.001; 2 / 4000 = 0.0005 so your ellipse takes 0.1% x 0.05% of the widget area.

[jesse_mark]

yeah i know, so this is why im asking if there is a way to make the size of the ellipce fixed, because the rect some times have big values and other may have small value.

so im asking if there is a way to make the ellipce has fixed size and will be showen with same size all the times.