83 lines
2.1 KiB
Go
83 lines
2.1 KiB
Go
package draw2dgl
|
|
|
|
import (
|
|
"git.fromouter.space/crunchy-rocks/draw2d"
|
|
"git.fromouter.space/crunchy-rocks/freetype/truetype"
|
|
|
|
"golang.org/x/image/math/fixed"
|
|
)
|
|
|
|
// DrawContour draws the given closed contour at the given sub-pixel offset.
|
|
func DrawContour(path draw2d.PathBuilder, ps []truetype.Point, dx, dy float64) {
|
|
if len(ps) == 0 {
|
|
return
|
|
}
|
|
startX, startY := pointToF64Point(ps[0])
|
|
path.MoveTo(startX+dx, startY+dy)
|
|
q0X, q0Y, on0 := startX, startY, true
|
|
for _, p := range ps[1:] {
|
|
qX, qY := pointToF64Point(p)
|
|
on := p.Flags&0x01 != 0
|
|
if on {
|
|
if on0 {
|
|
path.LineTo(qX+dx, qY+dy)
|
|
} else {
|
|
path.QuadCurveTo(q0X+dx, q0Y+dy, qX+dx, qY+dy)
|
|
}
|
|
} else {
|
|
if on0 {
|
|
// No-op.
|
|
} else {
|
|
midX := (q0X + qX) / 2
|
|
midY := (q0Y + qY) / 2
|
|
path.QuadCurveTo(q0X+dx, q0Y+dy, midX+dx, midY+dy)
|
|
}
|
|
}
|
|
q0X, q0Y, on0 = qX, qY, on
|
|
}
|
|
// Close the curve.
|
|
if on0 {
|
|
path.LineTo(startX+dx, startY+dy)
|
|
} else {
|
|
path.QuadCurveTo(q0X+dx, q0Y+dy, startX+dx, startY+dy)
|
|
}
|
|
}
|
|
|
|
func pointToF64Point(p truetype.Point) (x, y float64) {
|
|
return fUnitsToFloat64(p.X), -fUnitsToFloat64(p.Y)
|
|
}
|
|
|
|
func fUnitsToFloat64(x fixed.Int26_6) float64 {
|
|
scaled := x << 2
|
|
return float64(scaled/256) + float64(scaled%256)/256.0
|
|
}
|
|
|
|
// FontExtents contains font metric information.
|
|
type FontExtents struct {
|
|
// Ascent is the distance that the text
|
|
// extends above the baseline.
|
|
Ascent float64
|
|
|
|
// Descent is the distance that the text
|
|
// extends below the baseline. The descent
|
|
// is given as a negative value.
|
|
Descent float64
|
|
|
|
// Height is the distance from the lowest
|
|
// descending point to the highest ascending
|
|
// point.
|
|
Height float64
|
|
}
|
|
|
|
// Extents returns the FontExtents for a font.
|
|
// TODO needs to read this https://developer.apple.com/fonts/TrueType-Reference-Manual/RM02/Chap2.html#intro
|
|
func Extents(font *truetype.Font, size float64) FontExtents {
|
|
bounds := font.Bounds(fixed.Int26_6(font.FUnitsPerEm()))
|
|
scale := size / float64(font.FUnitsPerEm())
|
|
return FontExtents{
|
|
Ascent: float64(bounds.Max.Y) * scale,
|
|
Descent: float64(bounds.Min.Y) * scale,
|
|
Height: float64(bounds.Max.Y-bounds.Min.Y) * scale,
|
|
}
|
|
}
|