// DrawFontExtents draws some text and denotes the
// various extents and width with lines. Expects
// about a 4x4 inch canvas.
func DrawFontExtents(c vg.Canvas) {
x, y := vg.Inches(1), vg.Inches(2)
str := "Eloquent"
font, err := vg.MakeFont("Times-Roman", 18)
if err != nil {
panic(err)
}
width := font.Width(str)
ext := font.Extents()
des := ext.Descent
asc := ext.Ascent
c.FillString(font, x, y, str)
// baseline
path := vg.Path{}
path.Move(x, y)
path.Line(x+width, y)
c.Stroke(path)
// descent
c.SetColor(color.RGBA{G: 255, A: 255})
path = vg.Path{}
path.Move(x, y+des)
path.Line(x+width, y+des)
c.Stroke(path)
// ascent
c.SetColor(color.RGBA{B: 255, A: 255})
path = vg.Path{}
path.Move(x, y+asc)
path.Line(x+width, y+asc)
c.Stroke(path)
}
// DrawFonts draws some text in all of the various
// fonts along with a box to make sure that their
// sizes are computed correctly.
func DrawFonts(c vg.Canvas) {
y := vg.Points(0)
var fonts []string
for fname := range vg.FontMap {
fonts = append(fonts, fname)
}
sort.Strings(fonts)
for _, fname := range fonts {
font, err := vg.MakeFont(fname, 20)
if err != nil {
panic(err)
}
w := font.Width(fname + "Xqg")
h := font.Extents().Ascent
c.FillString(font, 0, y-font.Extents().Descent, fname+"Xqg")
fmt.Println(fname)
var path vg.Path
path.Move(0, y+h)
path.Line(w, y+h)
path.Line(w, y)
path.Line(0, y)
path.Close()
c.Stroke(path)
path = vg.Path{}
c.SetColor(color.RGBA{B: 255, A: 255})
c.SetLineDash([]vg.Length{vg.Points(5), vg.Points(3)}, 0)
path.Move(0, y-font.Extents().Descent)
path.Line(w, y-font.Extents().Descent)
c.Stroke(path)
c.SetColor(color.Black)
c.SetLineDash([]vg.Length{}, 0)
y += h
}
}
// DrawArcs draws some arcs to the canvas.
// The canvas is assumed to be 4 inches square.
func DrawArcs(c vg.Canvas) {
green := color.RGBA{G: 255, A: 255}
var p vg.Path
p.Move(vg.Inches(3), vg.Inches(2))
p.Arc(vg.Inches(2), vg.Inches(2), vg.Inches(1), 0, 2*math.Pi)
c.SetColor(color.RGBA{B: 255, A: 255})
c.Fill(p)
p = vg.Path{}
p.Move(vg.Inches(4), vg.Inches(2))
p.Line(vg.Inches(3), vg.Inches(2))
p.Arc(vg.Inches(2), vg.Inches(2), vg.Inches(1), 0, 5*math.Pi/2)
p.Line(vg.Inches(2), vg.Inches(4))
c.SetColor(color.RGBA{R: 255, A: 255})
c.SetLineWidth(vg.Points(3))
c.Stroke(p)
p = vg.Path{}
p.Move(vg.Inches(0), vg.Inches(2))
p.Line(vg.Inches(1), vg.Inches(2))
p.Arc(vg.Inches(2), vg.Inches(2), vg.Inches(1), math.Pi, -7*math.Pi/2)
p.Line(vg.Inches(2), vg.Inches(0))
c.SetColor(color.Black)
c.SetLineWidth(vg.Points(1))
c.Stroke(p)
p = vg.Path{}
p.Move(vg.Inches(0), vg.Inches(1))
p.Arc(vg.Inches(1), vg.Inches(1), vg.Inches(1), math.Pi, math.Pi/2)
c.SetLineWidth(vg.Points(3))
c.SetColor(green)
c.Stroke(p)
p = vg.Path{}
p.Move(vg.Inches(1), vg.Inches(0))
p.Arc(vg.Inches(1), vg.Inches(1), vg.Inches(1), 3*math.Pi/2, -math.Pi/2)
c.SetLineWidth(vg.Points(1))
c.SetColor(color.Black)
c.Stroke(p)
p = vg.Path{}
p.Move(vg.Inches(3), vg.Inches(2))
p.Arc(vg.Inches(3), vg.Inches(3), vg.Inches(1), 3*math.Pi/2, 3*math.Pi/2)
c.SetLineWidth(vg.Points(3))
c.SetColor(green)
c.Stroke(p)
p = vg.Path{}
p.Move(vg.Inches(2), vg.Inches(3))
p.Arc(vg.Inches(3), vg.Inches(3), vg.Inches(1), math.Pi, -3*math.Pi/2)
c.SetLineWidth(vg.Points(1))
c.SetColor(color.Black)
c.Stroke(p)
}