At first I didn't understand how a rectangle was involved with drawing these objects. After doing some experimenting I discovered that the rectangle is the bounding box for an ellipse, part of which makes up the arc, pie or chord. Nowhere have I seen it explicitly stated that this was how these objects were constructed. Nowhere have I found the more traditional method of specifying a centre and radius. Is there a simple explanation for this? I mean, sure it's one way of specifying things but it isn't intuitively obvious, especially with no explanation anywhere.

Thanks. I certainly could create a little function for turning centre & radius in to rectangle. It just interested me that this method was used. I shall as in devs area.

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Drawing Arcs, Pies, and Chords

Solved General and Desktop

3 Posts 2 Posters 749 Views

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BrianE

wrote on last edited by

#1

At first I didn't understand how a rectangle was involved with drawing these objects. After doing some experimenting I discovered that the rectangle is the bounding box for an ellipse, part of which makes up the arc, pie or chord.

Nowhere have I seen it explicitly stated that this was how these objects were constructed. Nowhere have I found the more traditional method of specifying a centre and radius. Is there a simple explanation for this? I mean, sure it's one way of specifying things but it isn't intuitively obvious, especially with no explanation anywhere.
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mrjj
Lifetime Qt Champion
wrote on last edited by

#2

Hi
Well it does show in the samples
http://doc.qt.io/qt-5/qpainter.html
that Rect are used for most operations.

If you need alternate way, it should be quite easy to add.

This is user oriented forums so if you are asking why the developers choose such way,
i'm not sure u will get answers here.

The devs hang out here
http://lists.qt-project.org/mailman/listinfo/
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BrianE

wrote on last edited by

#3

Thanks. I certainly could create a little function for turning centre & radius in to rectangle. It just interested me that this method was used. I shall as in devs area.
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