角度を指定するUI

GuruGuruUI.cpp

#include <Siv3D.hpp> // OpenSiv3D v0.6.4

void DrawAngleText(const Font& font, const Circle& circle, double angle, ColorF color)
{
	const auto degText = font(U"{:.1f}"_fmt(ToDegrees(angle)));
	degText.region(Arg::topCenter = circle.center + Vec2{ 0, circle.r + 2 }).draw(ColorF(Scene::GetBackground(), 0.8));
	degText.draw(Arg::topCenter = circle.center + Vec2{ 0, circle.r + 2 }, color);
}

void Main()
{
	Scene::SetBackground(ColorF(0.9));

	double angleA = 0;
	double angleB = 0;
	int dragState = 0;

	Font regular(20, Typeface::Regular);
	Font bold(20, Typeface::Bold);

	while (System::Update())
	{
		if (not MouseL.pressed())
		{
			dragState = 0;
		}

		if (dragState)
		{
			Vec2 diff = Cursor::PosF() - Scene::CenterF();
			if (diff.length() > 8)
			{
				double angle = std::atan2(-diff.y, diff.x);
				switch (dragState)
				{
				case 1:
					angleA = angle;
					break;
				case 2:
					angleB = angle;
					break;
				}
			}
		}

		{
			Transformer2D t(Mat3x2::Translate(Scene::CenterF()), TransformCursor::Yes);
			Vec2 posA = Vec2{ std::cos(angleA), -std::sin(angleA) } * 200;
			Vec2 posB = Vec2{ std::cos(angleB), -std::sin(angleB) } * 300;
			const Circle circleA(posA, 20);
			const Circle circleB(posB, 20);

			Line(-340, 0, 340, 0).draw(2, Palette::Lightgray);
			bold(U"+").draw(Arg::bottomCenter = Vec2{ 330, 1 }, Palette::Gray);
			bold(U"-").draw(Arg::topCenter = Vec2{ 330, -1 }, Palette::Gray);

			Line(0, 0, posB).draw(4, Palette::Darkred);
			circleB
				.draw(Palette::White)
				.drawFrame(dragState == 2 ? 4 : 2, Palette::Darkred);
			bold(U"B").drawAt(posB, Palette::Darkred);
			DrawAngleText(regular, circleB, angleB, Palette::Darkred);

			Line(0, 0, posA).draw(4, Palette::Darkblue);
			circleA
				.draw(Palette::White)
				.drawFrame(dragState == 1 ? 4 : 2, Palette::Darkblue);
			bold(U"A").drawAt(posA, Palette::Darkblue);
			DrawAngleText(regular, circleA, angleA, Palette::Darkblue);

			Circle(0, 0, 8).draw(Scene::GetBackground());

			if (MouseL.down())
			{
				if (circleA.mouseOver())
				{
					dragState = 1;
				}
				if (circleB.mouseOver())
				{
					dragState = 2;
				}
			}
		}

		ClearPrint();
		Print << U"A → B: " << ToDegrees(angleB - angleA);
		Print << U"A → B + 2π: " << ToDegrees(angleB + Math::TwoPi - angleA);
		Print << U"A → B - 2π: " << ToDegrees(angleB - Math::TwoPi - angleA);
	}
}