LibGfx: Quadratic Bezier curve

[EXL]

It seems that path with quadratic_bezier_curve_to() has some distortions compared to Qt 5, especially the fill. Maybe I'm using this method wrong?

@alimpfard @linusg

GIF Animation (open the image in full resolution in a new tab):

LibGfx Code:

void draw_rounded_rect(GUI::Painter &painter, const Gfx::Color &color, const Gfx::IntRect &rect, int rad, bool fill) {
	auto path = Gfx::Path();
	const float left = rect.left(), right = rect.right(), top = rect.top(), bottom = rect.bottom();
	path.move_to({ left + rad, top });
	path.line_to({ right - rad, top });
	path.quadratic_bezier_curve_to({ right, top }, { right, top + rad });
	path.line_to({ right, bottom - rad });
	path.quadratic_bezier_curve_to({ right, bottom }, { right - rad, bottom });
	path.line_to({ left + rad, bottom });
	path.quadratic_bezier_curve_to({ left, bottom }, { left, bottom - rad });
	path.line_to({ left, top + rad });
	path.quadratic_bezier_curve_to({ left, top }, { left + rad, top });
	path.close();
	painter.fill_path(path, color, Gfx::Painter::WindingRule::EvenOdd);
}

Qt 5 Code:

void drawRoundedRect(QPainter &painter, const QColor &color, const QRect &rect, int rad, bool fill) {
	int left = rect.left(), right = rect.right(), top = rect.top(), bottom = rect.bottom();
	QPainterPath p;
	p.moveTo(left + rad, top);
	p.lineTo(right - rad, top);
	p.quadTo(right, top, right, top + rad);
	p.lineTo(right, bottom - rad);
	p.quadTo(right, bottom, right - rad, bottom);
	p.lineTo(left + rad, bottom);
	p.quadTo(left, bottom, left, bottom - rad);
	p.lineTo(left, top + rad);
	p.quadTo(left, top, left + rad, top);
	p.closeSubpath();
	painter.fillPath(p, color);
}

Sample Code: QuadBezierSampleCode.zip

[alimpfard]

The lines could probably be made more similar by tweaking the "can approximate bezier curve" tolerance.
However the fill seems to consistently draw an extra pixel on the outline, perhaps we're drawing a border somehow?
I think @SrimantaBarua made a new path-filling impl (see the TTF PR), perhaps try that one and see if it gets rid of these artifacts?

[EXL]

However the fill seems to consistently draw an extra pixel on the outline, perhaps we're drawing a border somehow?

Interesting. Can anyone check this out?

I think @SrimantaBarua made a new path-filling impl (see the TTF PR), perhaps try that one and see if it gets rid of these artifacts?

Thanks, I tried with patches from #2512:

$ git fetch origin pull/2512/head:ttf
$ git checkout ttf
$ make install && make image && make run

Result:

1. LibGFX Original.
2. LibGFX with @SrimantaBarua patches.
3. Qt 5 Standard.

It's a little better, but the angles are still a bit different.

[MacDue]

Now we're in 2023 and LibGfx now looks like this:

I'd say this is now fixed :)