[Qt-interest] QPainter scale and rotate issue

[Yawar Amin]

Hi,

I'm trying to teach myself simple QPainter usage and I have a QWidget-derived class as per attachments. I'm capturing the paint event and trying to draw a Pythagorean tree [1] using a 3-4-5 right triangle as the basis, with the following steps:

1. Draw the square with the 5 side, i.e. the one that corresponds to the hypotenuse, scaled up to 100 units. Draw from the top-left corner of the square and place the square at the bottom of the widget area.

2. Rotate the painter by -120, scale up to 80 units, and draw the square corresponding to the 4 side.

3. Translate the painter to the top right corner of the square, rotate by -120, scale up to 60 units, and draw the square corresponding to the 3 side.

Now according to Pythagoras, the three squares should meet to form a right triangle. But the top two triangles end up never meeting, no matter how much I tweak the rotating and scaling.

Probably I'm doing something glaringly wrong? Can anyone comment?

Thanks,

Yawar

[1] http://en.wikipedia.org/wiki/Pythagoras_tree


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