Tabs support

go.mod

@@ -5,7 +5,7 @@ go 1.12
 require (
 	github.com/Kodeworks/golang-image-ico v0.0.0-20141118225523-73f0f4cfade9
 	github.com/akavel/rsrc v0.8.0 // indirect
-	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/fredbi/uri v0.0.0-20181227131451-3dcfdacbaaf3
 	github.com/fsnotify/fsnotify v1.4.9
 	github.com/fyne-io/mobile v0.1.2
 	github.com/go-gl/gl v0.0.0-20190320180904-bf2b1f2f34d7
@@ -28,7 +28,6 @@ require (
 	golang.org/x/tools v0.0.0-20200328031815-3db5fc6bac03
 	gopkg.in/check.v1 v1.0.0-20200227125254-8fa46927fb4f // indirect
 	gopkg.in/yaml.v2 v2.2.8 // indirect
-	github.com/fredbi/uri v0.0.0-20181227131451-3dcfdacbaaf3
 )
 
 replace github.com/go-gl/glfw/v3.3/glfw v0.0.0-20200625191551-73d3c3675aa3 => github.com/fyne-io/glfw/v3.3/glfw v0.0.0-20201123143003-f2279069162d

internal/painter/drawer.go

@@ -0,0 +1,83 @@
+package painter
+
+import (
+	"image"
+	"image/draw"
+	"log"
+	"math"
+
+	"golang.org/x/image/font"
+	"golang.org/x/image/math/fixed"
+)
+
+// FontDrawer extends "golang.org/x/image/font" to add support for tabs
+// FontDrawer draws text on a destination image.
+//
+// A FontDrawer is not safe for concurrent use by multiple goroutines, since its
+// Face is not.
+type FontDrawer struct {
+	font.Drawer
+}
+
+func tabStop(f font.Face, x fixed.Int26_6, tabWidth int) fixed.Int26_6 {
+	spacew, ok := f.GlyphAdvance(' ')
+	if !ok {
+		log.Print("Failed to find space width for tab")
+		return x
+	}
+	tabw := spacew * fixed.Int26_6(tabWidth)
+	tabs, _ := math.Modf(float64((x + tabw) / tabw))
+	return tabw * fixed.Int26_6(tabs)
+}
+
+// DrawString draws s at the dot and advances the dot's location.
+// Tabs are translated into a dot location change.
+func (d *FontDrawer) DrawString(s string, tabWidth int) {
+	prevC := rune(-1)
+	for _, c := range s {
+		if prevC >= 0 {
+			d.Dot.X += d.Face.Kern(prevC, c)
+		}
+		if c == '\t' {
+			d.Dot.X = tabStop(d.Face, d.Dot.X, tabWidth)
+		} else {
+			dr, mask, maskp, a, ok := d.Face.Glyph(d.Dot, c)
+			if !ok {
+				// TODO: is falling back on the U+FFFD glyph the responsibility of
+				// the Drawer or the Face?
+				// TODO: set prevC = '\ufffd'?
+				continue
+			}
+			draw.DrawMask(d.Dst, dr, d.Src, image.Point{}, mask, maskp, draw.Over)
+			d.Dot.X += a
+		}
+
+		prevC = c
+	}
+}
+
+// MeasureString returns how far dot would advance by drawing s with f.
+// Tabs are translated into a dot location change.
+func MeasureString(f font.Face, s string, tabWidth int) (advance fixed.Int26_6) {
+	prevC := rune(-1)
+	for _, c := range s {
+		if prevC >= 0 {
+			advance += f.Kern(prevC, c)
+		}
+		if c == '\t' {
+			advance = tabStop(f, advance, tabWidth)
+		} else {
+			a, ok := f.GlyphAdvance(c)
+			if !ok {
+				// TODO: is falling back on the U+FFFD glyph the responsibility of
+				// the Drawer or the Face?
+				// TODO: set prevC = '\ufffd'?
+				continue
+			}
+			advance += a
+		}
+
+		prevC = c
+	}
+	return advance
+}

internal/painter/font.go

@@ -31,7 +31,7 @@ func RenderedTextSize(text string, size float32, style fyne.TextStyle) fyne.Size
 	opts.DPI = TextDPI
 
 	face := CachedFontFace(style, &opts)
-	advance := font.MeasureString(face, text)
+	advance := MeasureString(face, text, style.TabWidth())
 
 	return fyne.NewSize(float32(advance.Ceil()), float32(face.Metrics().Height.Ceil()))
 }

internal/painter/gl/gl_common.go

@@ -7,7 +7,6 @@ import (
 
 	"github.com/goki/freetype"
 	"github.com/goki/freetype/truetype"
-	"golang.org/x/image/font"
 
 	"fyne.io/fyne/v2"
 	"fyne.io/fyne/v2/canvas"
@@ -84,12 +83,12 @@ func (p *glPainter) newGlTextTexture(obj fyne.CanvasObject) Texture {
 	opts.DPI = float64(painter.TextDPI * p.texScale)
 	face := painter.CachedFontFace(text.TextStyle, &opts)
 
-	d := font.Drawer{}
+	d := painter.FontDrawer{}
 	d.Dst = img
 	d.Src = &image.Uniform{C: text.Color}
 	d.Face = face
 	d.Dot = freetype.Pt(0, height-face.Metrics().Descent.Ceil())
-	d.DrawString(text.Text)
+	d.DrawString(text.Text, text.TextStyle.TabWidth())
 
 	return p.imgToTexture(img, canvas.ImageScaleSmooth)
 }

internal/painter/software/draw.go

@@ -13,7 +13,6 @@ import (
 	"github.com/goki/freetype"
 	"github.com/goki/freetype/truetype"
 	"golang.org/x/image/draw"
-	"golang.org/x/image/font"
 )
 
 type gradient interface {
@@ -145,12 +144,12 @@ func drawText(c fyne.Canvas, text *canvas.Text, pos fyne.Position, base *image.N
 	opts.DPI = painter.TextDPI
 	face := painter.CachedFontFace(text.TextStyle, &opts)
 
-	d := font.Drawer{}
+	d := painter.FontDrawer{}
 	d.Dst = txtImg
 	d.Src = &image.Uniform{C: text.Color}
 	d.Face = face
 	d.Dot = freetype.Pt(0, height-face.Metrics().Descent.Ceil())
-	d.DrawString(text.Text)
+	d.DrawString(text.Text, text.TextStyle.TabWidth())
 
 	size := text.Size()
 	offsetX := float32(0)

internal/test/util_test.go

@@ -8,10 +8,10 @@ import (
 	"os"
 	"testing"
 
+	"fyne.io/fyne/v2/internal/painter"
 	"github.com/goki/freetype"
 	"github.com/goki/freetype/truetype"
 	"github.com/stretchr/testify/require"
-	"golang.org/x/image/font"
 
 	"fyne.io/fyne/v2/internal/test"
 	"fyne.io/fyne/v2/theme"
@@ -28,13 +28,14 @@ func TestAssertImageMatches(t *testing.T) {
 	opts := truetype.Options{Size: 20, DPI: 96}
 	f, _ := truetype.Parse(theme.TextFont().Content())
 	face := truetype.NewFace(f, &opts)
-	d := font.Drawer{
-		Dst:  txtImg,
-		Src:  image.NewUniform(color.Black),
-		Face: face,
-		Dot:  freetype.Pt(0, 50-face.Metrics().Descent.Ceil()),
-	}
-	d.DrawString("Hello!")
+
+	d := painter.FontDrawer{}
+	d.Dst = txtImg
+	d.Src = image.NewUniform(color.Black)
+	d.Face = face
+	d.Dot = freetype.Pt(0, 50-face.Metrics().Descent.Ceil())
+
+	d.DrawString("Hello!", 4)
 	draw.Draw(img, bounds, txtImg, image.Point{}, draw.Over)
 
 	tt := &testing.T{}

test/testdriver.go

@@ -13,7 +13,6 @@ import (
 	"fyne.io/fyne/v2/storage/repository"
 
 	"github.com/goki/freetype/truetype"
-	"golang.org/x/image/font"
 )
 
 // SoftwarePainter describes a simple type that can render canvases
@@ -107,7 +106,7 @@ func (d *testDriver) RenderedTextSize(text string, size float32, style fyne.Text
 	opts.DPI = painter.TextDPI
 
 	face := painter.CachedFontFace(style, &opts)
-	advance := font.MeasureString(face, text)
+	advance := painter.MeasureString(face, text, style.TabWidth())
 
 	sws := fyne.NewSize(float32(advance.Ceil()), float32(face.Metrics().Height.Ceil()))
 	gls := painter.RenderedTextSize(text, size, style)

text.go

@@ -30,12 +30,33 @@ const (
 	TextWrapWord
 )
 
+const (
+	// DefaultTabWidth is the default width in spaces
+	DefaultTabWidth = 4
+)
+
 // TextStyle represents the styles that can be applied to a text canvas object
 // or text based widget.
 type TextStyle struct {
 	Bold      bool // Should text be bold
 	Italic    bool // Should text be italic
 	Monospace bool // Use the system monospace font instead of regular
+	tabWidth  int  // Width of tabs in spaces
+}
+
+// TabWidth either returns the set tab width or if not set the returns the DefaultTabWidth
+func (ts *TextStyle) TabWidth() int {
+	if ts.tabWidth == 0 {
+		return DefaultTabWidth
+	}
+	return ts.tabWidth
+}
+
+// SetTabWidth sets the tab width if the supplied value is greater than 0
+func (ts *TextStyle) SetTabWidth(tabWidth int) {
+	if tabWidth > 0 {
+		ts.tabWidth = tabWidth
+	}
 }
 
 // MeasureText uses the current driver to calculate the size of text when rendered.

widget/entry_internal_test.go

@@ -241,7 +241,7 @@ func TestEntry_Tab(t *testing.T) {
 	r := cache.Renderer(e.textProvider()).(*textRenderer)
 	assert.Equal(t, 3, len(r.texts))
 	assert.Equal(t, "a", r.texts[0].Text)
-	assert.Equal(t, textTabIndent+"b", r.texts[1].Text)
+	assert.Equal(t, "\tb", r.texts[1].Text)
 
 	w := test.NewWindow(e)
 	w.Resize(fyne.NewSize(86, 86))

widget/text.go

@@ -14,8 +14,6 @@ import (
 
 const (
 	passwordChar = "•"
-	// TODO move to complete tab handling, for now we just indent this far statically
-	textTabIndent = "    "
 )
 
 // textPresenter provides the widget specific information to a generic text provider
@@ -236,8 +234,6 @@ func (t *textProvider) lineSizeToColumn(col, row int) fyne.Size {
 	measureText := string(line[0:col])
 	if t.presenter.concealed() {
 		measureText = strings.Repeat(passwordChar, col)
-	} else {
-		measureText = strings.ReplaceAll(measureText, "\t", textTabIndent)
 	}
 
 	label := canvas.NewText(measureText, theme.ForegroundColor())
@@ -331,7 +327,7 @@ func (r *textRenderer) Refresh() {
 		if concealed {
 			line = strings.Repeat(passwordChar, len(row))
 		} else {
-			line = strings.ReplaceAll(string(row), "\t", textTabIndent)
+			line = string(row)
 		}
 
 		var textCanvas *canvas.Text