A rendering engine library for Go supporting both SDL2 and WebAssembly (HTML Canvas) targets.
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package render
import (
"fmt"
"strconv"
"strings"
)
// Point holds an X,Y coordinate value.
type Point struct {
X int
Y int
}
// Common points.
var (
Origin Point
)
// NewPoint makes a new Point at an X,Y coordinate.
func NewPoint(x, y int) Point {
return Point{
X: x,
Y: y,
}
}
func (p Point) String() string {
return fmt.Sprintf("%d,%d", p.X, p.Y)
}
// ParsePoint to parse a point from its string representation.
func ParsePoint(v string) (Point, error) {
halves := strings.Split(v, ",")
if len(halves) != 2 {
return Point{}, fmt.Errorf("'%s': not a valid coordinate string", v)
}
x, errX := strconv.Atoi(halves[0])
y, errY := strconv.Atoi(halves[1])
if errX != nil || errY != nil {
return Point{}, fmt.Errorf("invalid coordinate string (X: %v; Y: %v)",
errX,
errY,
)
}
return Point{
X: int(x),
Y: int(y),
}, nil
}
// IsZero returns if the point is the zero value.
func (p Point) IsZero() bool {
return p.X == 0 && p.Y == 0
}
// Inside returns whether the Point falls inside the rect.
//
// NOTICE: the W and H are zero-relative, so a 100x100 box at coordinate
// X,Y would still have W,H of 100.
func (p Point) Inside(r Rect) bool {
var (
x1 = r.X
y1 = r.Y
x2 = r.X + r.W
y2 = r.Y + r.H
)
return ((p.X >= x1 && p.X <= x2) &&
(p.Y >= y1 && p.Y <= y2))
}
// Add (or subtract) the other point to your current point.
func (p *Point) Add(other Point) {
p.X += other.X
p.Y += other.Y
}
// Subtract the other point from your current point.
func (p *Point) Subtract(other Point) {
p.X -= other.X
p.Y -= other.Y
}
// Compare the point to another, returning a delta coordinate.
//
// If the two points are equal the result has X=0 Y=0. Otherwise the X and Y
// return values will be positive or negative numbers of how you could modify
// the current Point to be equal to the other.
func (p *Point) Compare(other Point) Point {
return Point{
X: other.X - p.X,
Y: other.Y - p.Y,
}
}
// MarshalText to convert the point into text so that a render.Point may be used
// as a map key and serialized to JSON.
func (p *Point) MarshalText() ([]byte, error) {
return []byte(fmt.Sprintf("%d,%d", p.X, p.Y)), nil
}
// UnmarshalText to restore it from text.
func (p *Point) UnmarshalText(b []byte) error {
halves := strings.Split(strings.Trim(string(b), `"`), ",")
if len(halves) != 2 {
return fmt.Errorf("'%s': not a valid coordinate string", b)
}
x, errX := strconv.Atoi(halves[0])
y, errY := strconv.Atoi(halves[1])
if errX != nil || errY != nil {
return fmt.Errorf("Point.UnmarshalJSON: Atoi errors (X=%s Y=%s)",
errX,
errY,
)
}
p.X = int(x)
p.Y = int(y)
return nil
}