114 lines
3.0 KiB
Go
114 lines
3.0 KiB
Go
package geo
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import (
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"fmt"
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)
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// Rect describes a rectangle based on the position of its top-left corner and
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// size
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type Rect struct {
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TopLeft XY
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Size XY
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}
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// Edge returns the coordinate of the edge indicated by the given direction (Up,
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// Down, Left, or Right). The coordinate will be for the axis applicable to the
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// direction, so for Left/Right it will be the x coordinate and for Up/Down the
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// y.
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func (r Rect) Edge(dir XY) int {
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switch dir {
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case Up:
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return r.TopLeft[1]
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case Down:
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return r.TopLeft[1] + r.Size[1] - 1
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case Left:
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return r.TopLeft[0]
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case Right:
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return r.TopLeft[0] + r.Size[0] - 1
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default:
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panic(fmt.Sprintf("unsupported direction: %#v", dir))
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}
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}
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// Corner returns the position of the corner identified by the given directions
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// (Left/Right, Up/Down)
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func (r Rect) Corner(xDir, yDir XY) XY {
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switch {
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case r.Size[0] == 0 || r.Size[1] == 0:
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panic(fmt.Sprintf("rectangle with non-multidimensional size has no corners: %v", r.Size))
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case xDir == Left && yDir == Up:
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return r.TopLeft
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case xDir == Right && yDir == Up:
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return r.TopLeft.Add(r.Size.Mul(Right)).Add(XY{-1, 0})
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case xDir == Left && yDir == Down:
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return r.TopLeft.Add(r.Size.Mul(Down)).Add(XY{0, -1})
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case xDir == Right && yDir == Down:
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return r.TopLeft.Add(r.Size).Add(XY{-1, -1})
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default:
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panic(fmt.Sprintf("unsupported Corner args: %v, %v", xDir, yDir))
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}
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}
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// EdgeMidpoint returns the point which is the midpoint of the edge dientified by the
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// direction (Up/Down/Left/Right)
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func (r Rect) EdgeMidpoint(dir XY, rounder Rounder) XY {
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var a, b XY
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switch dir {
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case Up:
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a, b = r.Corner(Left, Up), r.Corner(Right, Up)
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case Down:
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a, b = r.Corner(Left, Down), r.Corner(Right, Down)
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case Left:
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a, b = r.Corner(Left, Up), r.Corner(Left, Down)
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case Right:
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a, b = r.Corner(Right, Up), r.Corner(Right, Down)
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default:
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panic(fmt.Sprintf("unsupported direction: %#v", dir))
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}
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mid := a.Midpoint(b, rounder)
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return mid
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}
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func (r Rect) halfSize(rounder Rounder) XY {
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return r.Size.Div(XY{2, 2}, rounder)
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}
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// Center returns the centerpoint of the rectangle, using the given Rounder to
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// resolve non-integers
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func (r Rect) Center(rounder Rounder) XY {
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return r.TopLeft.Add(r.halfSize(rounder))
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}
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// Translate returns an instance of Rect which is the same as this one but
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// translated by the given amount
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func (r Rect) Translate(by XY) Rect {
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r.TopLeft = r.TopLeft.Add(by)
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return r
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}
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// Centered returns an instance of Rect which is this one but translated to be
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// centered on the given point. It will use the given Rounder to resolve
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// non-integers
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func (r Rect) Centered(on XY, rounder Rounder) Rect {
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r.TopLeft = on.Sub(r.halfSize(rounder))
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return r
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}
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// Union returns the smallest Rect which encompasses the given Rect and the one
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// being called upon.
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func (r Rect) Union(r2 Rect) Rect {
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if r.Size == Zero {
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return r2
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} else if r2.Size == Zero {
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return r
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}
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tl := r.TopLeft.Min(r2.TopLeft)
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br := r.Corner(Right, Down).Max(r2.Corner(Right, Down))
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return Rect{
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TopLeft: tl,
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Size: br.Sub(tl).Add(XY{1, 1}),
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}
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}
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