Add Shape Tool for drawing polygons (#75)

* ⬠ Add polygon drawing tool

* 🔤 Minor fix of variable and function names

* ❌ Remove stroke

* ⌨️ Use N key as polygo tool shortcut.

* ⌨️ Now using key Y for polygons.

* ⌨️ The tooltip for the shortcut is fixed

core/document/src/shape_points.rs

@@ -0,0 +1,126 @@
+use std::{fmt, ops::Add};
+
+use kurbo::{PathEl, Point, Vec2};
+use log::info;
+
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub struct ShapePoints {
+	center: kurbo::Point,
+	extent: kurbo::Vec2,
+	sides: u8,
+}
+
+impl ShapePoints {
+	/// A new shape from center, a point and the number of points.
+	#[inline]
+	pub fn new(center: impl Into<Point>, extent: impl Into<Vec2>, sides: u8) -> ShapePoints {
+		ShapePoints {
+			center: center.into(),
+			extent: extent.into(),
+			sides: sides,
+		}
+	}
+
+	// Gets the angle in radians between the longest line from the center and the apothem.
+	#[inline]
+	pub fn apothem_offset_angle(&self) -> f64 {
+		std::f64::consts::PI / (self.sides as f64)
+	}
+
+	// Gets the apothem (the shortest distance from the center to the edge)
+	#[inline]
+	pub fn apothem(&self) -> f64 {
+		self.apothem_offset_angle().cos() * (self.sides as f64)
+	}
+
+	// Gets the length of one side
+	#[inline]
+	pub fn side_length(&self) -> f64 {
+		self.apothem_offset_angle().sin() * (self.sides as f64) * (2 as f64)
+	}
+}
+
+impl std::fmt::Display for ShapePoints {
+	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+		fn rotate(v: &Vec2, theta: f64) -> Vec2 {
+			let cosine = theta.cos();
+			let sine = theta.sin();
+			return Vec2::new(v.x * cosine - v.y * sine, v.x * sine + v.y * cosine);
+		}
+		info!("sides{}", self.sides);
+		for i in 0..self.sides {
+			let radians = self.apothem_offset_angle() * ((i * 2 + (self.sides % 2)) as f64);
+			let offset = rotate(&self.extent, radians);
+			let point = self.center + offset;
+			write!(f, "{},{} ", point.x, point.y)?;
+		}
+
+		Ok(())
+	}
+}
+
+#[doc(hidden)]
+pub struct ShapePathIter {
+	shape: ShapePoints,
+	ix: usize,
+}
+
+impl Iterator for ShapePathIter {
+	type Item = PathEl;
+
+	fn next(&mut self) -> Option<PathEl> {
+		fn rotate(v: &Vec2, theta: f64) -> Vec2 {
+			let cosine = theta.cos();
+			let sine = theta.sin();
+			return Vec2::new(v.x * cosine - v.y * sine, v.x * sine + v.y * cosine);
+		}
+		self.ix += 1;
+		match self.ix {
+			1 => Some(PathEl::MoveTo(self.shape.center + self.shape.extent)),
+			_ => {
+				let radians = self.shape.apothem_offset_angle() * ((self.ix * 2 + (self.shape.sides % 2) as usize) as f64);
+				let offset = rotate(&self.shape.extent, radians);
+				let point = self.shape.center + offset;
+				Some(PathEl::LineTo(point))
+			}
+		}
+	}
+}
+
+impl Add<Vec2> for ShapePoints {
+	type Output = ShapePoints;
+
+	#[inline]
+	fn add(self, movement: Vec2) -> ShapePoints {
+		ShapePoints {
+			center: self.center + movement,
+			extent: self.extent,
+			sides: self.sides,
+		}
+	}
+}
+
+impl kurbo::Shape for ShapePoints {
+	type PathElementsIter = ShapePathIter;
+	#[inline]
+	fn perimeter(&self, _accuracy: f64) -> f64 {
+		self.side_length() * (self.sides as f64)
+	}
+
+	#[inline]
+	fn area(&self) -> f64 {
+		self.apothem() * self.perimeter(2.1)
+	}
+
+	fn path_elements(&self, _tolerance: f64) -> Self::PathElementsIter {
+		todo!()
+	}
+
+	fn winding(&self, _pt: Point) -> i32 {
+		todo!()
+	}
+
+	fn bounding_box(&self) -> kurbo::Rect {
+		todo!()
+	}
+}