text: deprecate BoundString

After we found a correct definition of the term 'dot', BoundString seems
less useful than expected. In order to adjust the position of a text, we
should use a face's Metrics and a string's advance (font.MeasureString).

examples/text/main.go

@@ -19,10 +19,12 @@ import (
 	"log"
 	"math"
 	"math/rand"
+	"strings"
 	"time"
 
 	"golang.org/x/image/font"
 	"golang.org/x/image/font/opentype"
+	"golang.org/x/image/math/fixed"
 
 	"github.com/hajimehoshi/ebiten/v2"
 	"github.com/hajimehoshi/ebiten/v2/examples/resources/fonts"
@@ -87,19 +89,45 @@ func (g *Game) Update() error {
 	return nil
 }
 
+func boundString(face font.Face, str string) fixed.Rectangle26_6 {
+	str = strings.TrimRight(str, "\n")
+	lines := strings.Split(str, "\n")
+	if len(lines) == 0 {
+		return fixed.Rectangle26_6{}
+	}
+
+	minX := fixed.I(0)
+	maxX := fixed.I(0)
+	for _, line := range lines {
+		a := font.MeasureString(face, line)
+		if maxX < a {
+			maxX = a
+		}
+	}
+
+	m := face.Metrics()
+	minY := -m.Ascent
+	maxY := fixed.Int26_6(len(lines)-1)*m.Height + m.Descent
+	return fixed.Rectangle26_6{fixed.Point26_6{X: minX, Y: minY}, fixed.Point26_6{X: maxX, Y: maxY}}
+}
+
+func fixed26_6ToFloat32(x fixed.Int26_6) float32 {
+	return float32(x>>6) + float32(x&((1<<6)-1))/(1<<6)
+}
+
 func (g *Game) Draw(screen *ebiten.Image) {
 	gray := color.RGBA{0x80, 0x80, 0x80, 0xff}
 
 	{
 		const x, y = 20, 40
-		b := text.BoundString(mplusNormalFont, sampleText)
+		b := boundString(mplusNormalFont, sampleText)
-		vector.DrawFilledRect(screen, float32(b.Min.X+x), float32(b.Min.Y+y), float32(b.Dx()), float32(b.Dy()), gray, false)
+		vector.DrawFilledRect(screen, fixed26_6ToFloat32(b.Min.X)+x, fixed26_6ToFloat32(b.Min.Y)+y, fixed26_6ToFloat32(b.Max.X-b.Min.X), fixed26_6ToFloat32(b.Max.Y-b.Min.Y), gray, false)
 		text.Draw(screen, sampleText, mplusNormalFont, x, y, color.White)
 	}
 	{
 		const x, y = 20, 140
-		b := text.BoundString(mplusBigFont, sampleText)
+		b := boundString(mplusBigFont, sampleText)
-		vector.DrawFilledRect(screen, float32(b.Min.X+x), float32(b.Min.Y+y), float32(b.Dx()), float32(b.Dy()), gray, false)
+		vector.DrawFilledRect(screen, fixed26_6ToFloat32(b.Min.X)+x, fixed26_6ToFloat32(b.Min.Y)+y, fixed26_6ToFloat32(b.Max.X-b.Min.X), fixed26_6ToFloat32(b.Max.Y-b.Min.Y), gray, false)
 		text.Draw(screen, sampleText, mplusBigFont, x, y, color.White)
 	}
 	{
@@ -113,8 +141,8 @@ func (g *Game) Draw(screen *ebiten.Image) {
 	{
 		const x, y = 160, 240
 		const lineHeight = 80
-		b := text.BoundString(text.FaceWithLineHeight(mplusBigFont, lineHeight), sampleText)
+		b := boundString(text.FaceWithLineHeight(mplusBigFont, lineHeight), sampleText)
-		vector.DrawFilledRect(screen, float32(b.Min.X+x), float32(b.Min.Y+y), float32(b.Dx()), float32(b.Dy()), gray, false)
+		vector.DrawFilledRect(screen, fixed26_6ToFloat32(b.Min.X)+x, fixed26_6ToFloat32(b.Min.Y)+y, fixed26_6ToFloat32(b.Max.X-b.Min.X), fixed26_6ToFloat32(b.Max.Y-b.Min.Y), gray, false)
 		text.Draw(screen, sampleText, text.FaceWithLineHeight(mplusBigFont, lineHeight), x, y, color.White)
 	}
 	{

text/text.go

@@ -149,11 +149,6 @@ var textM sync.Mutex
 //
 // clr is the color for text rendering.
 //
-// If you want to adjust the position of the text, these functions are useful:
-//
-//   - text.BoundString:                     the rendered bounds of the given text.
-//   - golang.org/x/image/font.Face.Metrics: the metrics of the face.
-//
 // The '\n' newline character puts the following text on the next line.
 // Line height is based on Metrics().Height of the font.
 //
@@ -190,11 +185,6 @@ func Draw(dst *ebiten.Image, text string, face font.Face, x, y int, clr color.Co
 // Be careful that the origin point is not upper-left corner position of dst.
 // The default glyph color is white. op's ColorM adjusts the color.
 //
-// If you want to adjust the position of the text, these functions are useful:
-//
-//   - text.BoundString:                     the rendered bounds of the given text.
-//   - golang.org/x/image/font.Face.Metrics: the metrics of the face.
-//
 // The '\n' newline character puts the following text on the next line.
 // Line height is based on Metrics().Height of the font.
 //
@@ -286,6 +276,8 @@ func DrawWithOptions(dst *ebiten.Image, text string, face font.Face, options *eb
 // This is a known issue (#498).
 //
 // BoundString is concurrent-safe.
+//
+// Deprecated: as of v2.6. Use golang.org/x/image/font.BoundString instead, or use a face's Metrics (Ascent and Descent) and font.MeasureString instead.
 func BoundString(face font.Face, text string) image.Rectangle {
 	textM.Lock()
 	defer textM.Unlock()