Function ButtonAt

Siv3D/src/Siv3D/SimpleGUI/SivSimpleGUI.cpp:147–184

		}

		bool ButtonAt(const StringView label, const Vec2& center, const Optional<double>& _width, const bool enabled)
		{
			const Font& font = GetFont();
			const auto dtext = font(label);

			const double labelWidth = Math::Ceil(dtext.region().w);
			const double width = _width.value_or_eval([&](){ return (labelWidth + 40); });

			const RectF rect{ Arg::center = center, width, UnitSize };
			const Vec2 labelPos{ (rect.x + (width - labelWidth) / 2.0), (center.y - font.height() / 2.0 + FontYOffset) };

			const bool mouseOver = (enabled && rect.mouseOver());
			const bool pushed = (mouseOver && Cursor::OnClientRect() && MouseL.down());
			const RoundRect rrect = rect.rounded(RoundSize);

			if (enabled)
			{
				rrect.draw(mouseOver ? ButtonMouseOverColor : BackgroundColor);
			}
			else
			{
				rrect.draw(DisabledBackgroundColor);
			}

			if (not pushed)
			{
				rrect.drawFrame(1, 0, FrameColor);
			}

			dtext.draw(labelPos, GetTextColor(enabled));

			if (mouseOver)
			{
				Cursor::RequestStyle(CursorStyle::Hand);
			}

			return pushed;
		}

		RectF SliderRegion(const Vec2& pos, double labelWidth, double sliderWidth)
		{