The new alignment method works

Closes #1

README.md

@@ -1,6 +1,8 @@
 # typeset
 
+[![Go Reference](https://pkg.go.dev/badge/git.tebibyte.media/tomo/typeset.svg)](https://pkg.go.dev/git.tebibyte.media/tomo/typeset)
+
 Typeset provides utilities for text layout, wrapping, and rendering.
 
 The state of a text layout is stored in a TypeSetter, and it can be drawn to any
-image.Image using a Drawer which "extends" TypeSetter.
+draw.Image using a Drawer which "extends" TypeSetter.

drawer.go

@@ -13,25 +13,31 @@ type Drawer struct { TypeSetter }
 // Draw draws the drawer's text onto the specified canvas at the given offset.
 func (drawer Drawer) Draw (
 	destination draw.Image,
-	color       color.Color,
+	col         color.Color,
 	offset      image.Point,
 ) (
 	updatedRegion image.Rectangle,
 ) {
-	source := image.NewUniform(color)
+	source := image.NewUniform(col)
 	
-	drawer.For (func (
+	drawer.ForRunes (func (
 		index    int,
 		char     rune,
 		position fixed.Point26_6,
 	) bool {
+		// leave empty space for space characters
+		if unicode.IsSpace(char) {
+			return true
+		}
+		
+		dot := fixed.P (
+			offset.X + position.X.Round(),
+			offset.Y + position.Y.Round())
 		destinationRectangle,
-		mask, maskPoint, _, ok := drawer.face.Glyph (
-			fixed.P (
-				offset.X + position.X.Round(),
-				offset.Y + position.Y.Round()),
-			char)
-		if !ok || unicode.IsSpace(char) || char == 0 {
+		mask, maskPoint, _, ok := drawer.face.Glyph(dot, char)
+		// tofu
+		if !ok {
+			drawer.drawTofu(char, destination, col, dot)
 			return true
 		}
 
@@ -50,3 +56,29 @@ func (drawer Drawer) Draw (
 	})
 	return
 }
+
+func (drawer Drawer) drawTofu (
+	char rune,
+	destination draw.Image,
+	col         color.Color,
+	position    fixed.Point26_6,
+) {
+	bounds, _ := tofuBounds(drawer.face)
+	rectBounds := image.Rect (
+		bounds.Min.X.Round(),
+		bounds.Min.Y.Round(),
+		bounds.Max.X.Round(),
+		bounds.Max.Y.Round()).Add(image.Pt(
+			position.X.Round(),
+			position.Y.Round()))
+	for x := rectBounds.Min.X; x < rectBounds.Max.X; x ++ {
+		destination.Set(x, rectBounds.Min.Y, col)
+	}
+	for y := rectBounds.Min.Y; y < rectBounds.Max.Y; y ++ {
+		destination.Set(rectBounds.Min.X, y, col)
+		destination.Set(rectBounds.Max.X - 1, y, col)
+	}
+	for x := rectBounds.Min.X; x < rectBounds.Max.X; x ++ {
+		destination.Set(x, rectBounds.Max.Y - 1, col)
+	}
+}

layout.go

@@ -8,12 +8,11 @@ import "golang.org/x/image/math/fixed"
 type Align int
 
 const (
-	// AlignLeft aligns the start of each line to the beginning point
-	// of each dot.
-	AlignLeft Align = iota
-	AlignRight
-	AlignCenter
-	AlignJustify
+	//                              X     |     Y
+	AlignStart  Align = iota // left      | top
+	AlignMiddle              // center    | center
+	AlignEnd                 // right     | bottom
+	AlignEven                // justified | evenly spaced
 )
 
 // RuneLayout contains layout information for a single rune relative to its
@@ -59,13 +58,16 @@ func DoWord (text []rune, face font.Face) (word WordLayout, remaining []rune) {
 		
 		// consume and process the rune
 		remaining = remaining[1:]
-		_, advance, ok := face.GlyphBounds(char)
-		if !ok { continue }
-		word.Runes = append (word.Runes, RuneLayout {
+		advance, ok := face.GlyphAdvance(char)
+		if !ok {
+			advance = tofuAdvance(face)
+		}
+		runeLayout := RuneLayout {
 			X:     x,
 			Width: advance,
 			Rune:  char,
-		})
+		}
+		word.Runes = append(word.Runes, runeLayout)
 
 		// advance
 		if gettingSpace {
@@ -111,20 +113,18 @@ type LineLayout struct {
 // wrap is set to true, this function will stop processing words once maxWidth
 // is crossed. The word which would have crossed over the limit will not be
 // processed.
-func DoLine (text []rune, face font.Face, wrap bool, maxWidth fixed.Int26_6) (line LineLayout, remaining []rune) {
+func DoLine (text []rune, face font.Face, wrap bool, width fixed.Int26_6) (line LineLayout, remaining []rune) {
 	remaining    = text
 	x           := fixed.Int26_6(0)
-	lastWord    := WordLayout { }
 	isFirstWord := true
 	for {
 		// process one word
 		word, remainingFromWord := DoWord(remaining, face)
-		word.X = x
 		x += word.Width
 
-		// if we have gone over the maximum width, stop processing
+		// if we have gone over the preferred width, stop processing
 		// words (if wrap is enabled)
-		if !isFirstWord && wrap && x > maxWidth {
+		if !isFirstWord && wrap && x > width {
 			break
 		}
 
@@ -133,7 +133,6 @@ func DoLine (text []rune, face font.Face, wrap bool, maxWidth fixed.Int26_6) (li
 
 		// if the word actually has contents, add it
 		if word.Runes != nil {
-			lastWord   = word
 			line.Words = append(line.Words, word)
 		}
 
@@ -149,9 +148,12 @@ func DoLine (text []rune, face font.Face, wrap bool, maxWidth fixed.Int26_6) (li
 	}
 
 	// set the width of the line's content.
-	line.Width        = maxWidth
-	line.ContentWidth = lastWord.X + lastWord.Width
-	line.SpaceAfter   = lastWord.SpaceAfter
+	line.Width = width
+	if len(line.Words) > 0 {
+		lastWord := line.Words[len(line.Words) - 1]
+		line.ContentWidth = x - lastWord.SpaceAfter
+		line.SpaceAfter   = lastWord.SpaceAfter
+	}
 	return
 }
 
@@ -168,30 +170,45 @@ func (line *LineLayout) Length () int {
 
 // Align aligns the text in the line according to the specified alignment
 // method.
-func (line *LineLayout) Align (align Align) {
+func (line *LineLayout) Align (align Align, tabWidth fixed.Int26_6) {
 	if len(line.Words) == 0 { return }
+	
+	if align == AlignEven {
+		line.justify(tabWidth)
+	} else {
+		line.contract(tabWidth)
+		
+		var leftOffset fixed.Int26_6
+		if align == AlignMiddle {
+			leftOffset = (line.Width - line.ContentWidth) / 2
+		} else if align == AlignEnd {
+			leftOffset = line.Width - line.ContentWidth
+		}
 
-	if align == AlignJustify {
-		line.justify()
-		return
-	}
-
-	leftOffset := -line.Words[0].X
-
-	if align == AlignCenter {
-		leftOffset += (line.Width - line.ContentWidth) / 2
-	} else if align == AlignRight {
-		leftOffset += line.Width - line.ContentWidth
-	}
-
-	for index := range line.Words {
-		line.Words[index].X += leftOffset
+		for index := range line.Words {
+			line.Words[index].X += leftOffset
+		}
 	}
 }
 
-func (line *LineLayout) justify () {
-	if len(line.Words) < 2 {
-		line.Align(AlignLeft)
+// assume line has content > 0
+func (line *LineLayout) contract (tabWidth fixed.Int26_6) {
+	x := fixed.Int26_6(0)
+	for index, word := range line.Words {
+		word.X = x
+		x += word.Width
+		x += word.SpaceAfter
+		line.Words[index] = word
+	}
+	lastWord := line.Words[len(line.Words) - 1]
+	line.ContentWidth = lastWord.X + lastWord.Width
+	line.SpaceAfter   = lastWord.SpaceAfter
+}
+
+// assume line has content > 0
+func (line *LineLayout) justify (tabWidth fixed.Int26_6) {
+	if len(line.Words) <= 1 {
+		line.Align(AlignStart, tabWidth)
 		return
 	}
 
@@ -202,11 +219,27 @@ func (line *LineLayout) justify () {
 		trueContentWidth += word.Width
 	}
 
-	spaceCount   := fixed.Int26_6(len(line.Words) - 1)
-	spacePerWord := (line.Width - trueContentWidth) / spaceCount
+	spaceCount   := len(line.Words) - 1
+	spacePerWord := (line.Width - trueContentWidth) / fixed.Int26_6(spaceCount)
 	x := fixed.Int26_6(0)
 	for index, word := range line.Words {
 		line.Words[index].X = x
 		x += spacePerWord + word.Width
 	}
 }
+
+func tofuAdvance (face font.Face) fixed.Int26_6 {
+	if advance, ok := face.GlyphAdvance('M'); ok {
+		return advance
+	} else {
+		return 16
+	}
+}
+
+func tofuBounds (face font.Face) (fixed.Rectangle26_6, fixed.Int26_6) {
+	if bounds, advance, ok := face.GlyphBounds('M'); ok {
+		return bounds, advance
+	} else {
+		return fixed.R(0, -16, 14, 0), 16
+	}
+}

setter.go

@@ -14,11 +14,11 @@ type TypeSetter struct {
 	layoutClean bool
 	alignClean  bool
 	
-	align Align
-	face  font.Face
-	maxWidth  int
-	maxHeight int
-	wrap      bool
+	hAlign, vAlign Align
+	face           font.Face
+	width, height  int
+	wrap           bool
+	tabWidth       fixed.Int26_6
 	
 	minWidth          fixed.Int26_6
 	layoutBounds      image.Rectangle
@@ -34,23 +34,16 @@ func (setter *TypeSetter) needLayout () {
 	setter.layoutBounds      = image.Rectangle { }
 	setter.layoutBoundsSpace = image.Rectangle { }
 	setter.minWidth          = 0
-	if len(setter.text) == 0 { return }
-	if setter.face  == nil { return }
+	if setter.face == nil { return }
 
 	horizontalExtent      := fixed.Int26_6(0)
 	horizontalExtentSpace := fixed.Int26_6(0)
+	metrics               := setter.face.Metrics()
+	remaining             := setter.text
+	y                     := fixed.Int26_6(0)
 
-	metrics   := setter.face.Metrics()
-	remaining := setter.text
-	y         := fixed.Int26_6(0)
-	for len(remaining) > 0 {
-		// process one line
-		line, remainingFromLine := DoLine (
-			remaining, setter.face, setter.wrap,
-			fixed.I(setter.maxWidth))
-		remaining = remainingFromLine
-
-		// add the line
+	// function to add line and update bounds statistics
+	addLine := func (line LineLayout) {
 		line.Y = y
 		y += metrics.Height
 		if line.ContentWidth > horizontalExtent {
@@ -62,23 +55,39 @@ func (setter *TypeSetter) needLayout () {
 		}
 		setter.lines = append(setter.lines, line)
 	}
-	setter.minWidth = horizontalExtentSpace
 
-	setter.layoutBounds.Max.X      = setter.maxWidth
-	setter.layoutBoundsSpace.Max.X = setter.maxWidth
+	// process every line until there are no more remaining runes
+	for len(remaining) > 0 {
+		line, remainingFromLine := DoLine (
+			remaining, setter.face, setter.wrap,
+			fixed.I(setter.width))
+		remaining = remainingFromLine
+		addLine(line)
+	}
+
+	// if there were no lines processed or the last line has a break after
+	// it, add a blank line at the end
+	needBlankLine :=
+		len(setter.lines) == 0 ||
+		setter.lines[len(setter.lines) - 1].BreakAfter
+	if needBlankLine { addLine(LineLayout { }) }
+
+	// if we are wrapping text, the width must be the user-set width
+	if setter.wrap {
+		horizontalExtent      = fixed.I(setter.width)
+		horizontalExtentSpace = fixed.I(setter.width) 
+	}
+
+	// calculate layout boundaries
+	setter.minWidth = horizontalExtentSpace
+	setter.layoutBounds.Max.X      = horizontalExtent.Round()
+	setter.layoutBoundsSpace.Max.X = horizontalExtentSpace.Round()
 
 	y -= metrics.Height
-	if setter.maxHeight == 0 {
-		setter.layoutBounds.Min.Y = -metrics.Ascent.Round()
-		setter.layoutBounds.Max.Y =
-			y.Round() +
-			metrics.Descent.Round()
-	} else {
-		setter.layoutBounds.Min.Y = -metrics.Ascent.Round()
-		setter.layoutBounds.Max.Y =
-			setter.maxHeight -
-			metrics.Ascent.Round()
-	}
+	setter.layoutBounds.Min.Y = -metrics.Ascent.Round()
+	setter.layoutBounds.Max.Y =
+		y.Round() +
+		metrics.Descent.Round()
 	setter.layoutBoundsSpace.Min.Y = setter.layoutBounds.Min.Y
 	setter.layoutBoundsSpace.Max.Y = setter.layoutBounds.Max.Y
 }
@@ -88,12 +97,73 @@ func (setter *TypeSetter) needAlignedLayout () {
 	setter.needLayout()
 	setter.alignClean = true
 
+	setter.alignHorizontally()
+	setter.alignVertically()
+}
+
+// should only be called from within setter.needAlignedLayout
+func (setter *TypeSetter) alignHorizontally () {
+	if len(setter.lines) == 0 { return }
+	
 	for index := range setter.lines {
-		align := setter.align
-		if index == len(setter.lines) - 1 && align == AlignJustify {
-			align = AlignLeft
+		align := setter.hAlign
+
+		// if the horizontal align is even, align lines with breaks
+		// after them to the left anyways
+		if align == AlignEven {
+			except :=
+				index == len(setter.lines) - 1 ||
+				setter.lines[index].BreakAfter
+			if except { align = AlignStart }
 		}
-		setter.lines[index].Align(align)
+
+		// align line
+		setter.lines[index].Align(align, setter.tabWidth)
+	}
+}
+
+// should only be called from within setter.needAlignedLayout
+func (setter *TypeSetter) alignVertically () {
+	if setter.height     == 0 { return }
+	if len(setter.lines) == 0 { return }
+	if setter.vAlign == AlignEven {
+		setter.justifyVertically()
+		return
+	}
+
+	// determine how much to shift lines
+	topOffset     := fixed.I(0)
+	contentHeight := setter.layoutBoundsSpace.Dy()
+	if setter.vAlign == AlignMiddle {
+		topOffset += fixed.I((setter.height - contentHeight) / 2)
+	} else if setter.vAlign == AlignEnd {
+		topOffset += fixed.I(setter.height - contentHeight)
+	}
+
+	// we may be re-aligning already aligned text. if the text is shifted
+	// away from the origin, account for that.
+	if len(setter.lines) > 0 {
+		topOffset -= setter.lines[0].Y
+	}
+
+	// shift lines
+	for index := range setter.lines {
+		setter.lines[index].Y += topOffset
+	}
+}
+
+// should only be called from within setter.alignVertically
+func (setter *TypeSetter) justifyVertically () {
+	spaceCount    := len(setter.lines) - 1
+	contentHeight := setter.layoutBoundsSpace.Dy()
+	spacePerLine  :=
+		fixed.Int26_6(setter.height - contentHeight) /
+		fixed.Int26_6(spaceCount)
+	
+	y := fixed.Int26_6(0)
+	for index := range setter.lines {
+		setter.lines[index].Y = y
+		y += spacePerLine + setter.LineHeight()
 	}
 }
 
@@ -105,10 +175,11 @@ func (setter *TypeSetter) SetWrap (wrap bool) {
 }
 
 // SetAlign sets the alignment method of the typesetter.
-func (setter *TypeSetter) SetAlign (align Align) {
-	if setter.align == align { return }
+func (setter *TypeSetter) SetAlign (horizontal, vertical Align) {
+	if setter.hAlign == horizontal && setter.vAlign == vertical { return }
 	setter.alignClean = false
-	setter.align = align
+	setter.hAlign = horizontal
+	setter.vAlign = vertical
 }
 
 // SetText sets the text content of the typesetter.
@@ -126,22 +197,31 @@ func (setter *TypeSetter) SetFace (face font.Face) {
 	setter.face = face
 }
 
-// SetMaxWidth sets the maximum width of the typesetter.
-func (setter *TypeSetter) SetMaxWidth (width int) {
-	if setter.maxWidth == width { return }
+// SetWidth sets the width of the typesetter. Text will still be able
+// to overflow outside of this width if wrapping is disabled.
+func (setter *TypeSetter) SetWidth (width int) {
+	if setter.width == width { return }
 	setter.layoutClean = false
 	setter.alignClean  = false
-	setter.maxWidth = width
+	setter.width = width
 }
 
-// SetMaxHeight sets the maximum height of the typesetter. If the maximum height
-// is greater than zero, no lines will be laid out past that point. If the
-// maximum height is zero, the text's maximum height will not be constrained.
-func (setter *TypeSetter) SetMaxHeight (heignt int) {
-	if setter.maxHeight == heignt { return }
+// SetHeight sets the height of the typesetter. If the height is greater than
+// zero, no lines will be laid out past it. If the height is zero, the text's
+// maximum height will not be constrained.
+func (setter *TypeSetter) SetHeight (heignt int) {
+	if setter.height == heignt { return }
 	setter.layoutClean = false
 	setter.alignClean  = false
-	setter.maxHeight = heignt
+	setter.height = heignt
+}
+
+// SetTabWidth sets the distance between tab stops.
+func (setter *TypeSetter) SetTabWidth (tabWidth fixed.Int26_6) {
+	if setter.tabWidth == tabWidth { return }
+	setter.layoutClean = false
+	setter.alignClean  = false
+	setter.tabWidth = tabWidth
 }
 
 // Em returns the width of one emspace according to the typesetter's font, which
@@ -158,15 +238,14 @@ func (setter *TypeSetter) LineHeight () fixed.Int26_6 {
 	return setter.face.Metrics().Height
 }
 
-// MaxWidth returns the maximum width of the typesetter as set by SetMaxWidth.
-func (setter *TypeSetter) MaxWidth () int {
-	return setter.maxWidth
+// Width returns the height of the typesetter as set by SetWidth.
+func (setter *TypeSetter) Width () int {
+	return setter.width
 }
 
-// MaxHeight returns the maximum height of the typesetter as set by
-// SetMaxHeight.
-func (setter *TypeSetter) MaxHeight () int {
-	return setter.maxHeight
+// Height returns the height of the typesetter as set by SetHeight.
+func (setter *TypeSetter) Height () int {
+	return setter.height
 }
 
 // Face returns the TypeSetter's font face as set by SetFace.
@@ -189,8 +268,18 @@ type RuneIterator func (
 )
 
 // For calls the specified iterator for every rune in the typesetter. If the
-// iterator returns false, the loop will immediately stop.
+// iterator returns false, the loop will immediately stop. This method will
+// insert a fake null rune at the end.
 func (setter *TypeSetter) For (iterator RuneIterator) {
+	setter.forInternal(iterator, true)
+}
+
+// ForRunes is like For, but leaves out the fake null rune.
+func (setter *TypeSetter) ForRunes (iterator RuneIterator) {
+	setter.forInternal(iterator, false)
+}
+
+func (setter *TypeSetter) forInternal (iterator RuneIterator, fakeNull bool) {
 	setter.needAlignedLayout()
 
 	index := 0
@@ -201,7 +290,7 @@ func (setter *TypeSetter) For (iterator RuneIterator) {
 		for _, word := range line.Words {
 		for _, char := range word.Runes {
 			lastCharRightBound = word.X + char.X + char.Width
-			keepGoing := iterator (index, char.Rune, fixed.Point26_6 {
+			keepGoing := iterator(index, char.Rune, fixed.Point26_6 {
 				X: word.X + char.X,
 				Y: line.Y,
 			})
@@ -210,21 +299,24 @@ func (setter *TypeSetter) For (iterator RuneIterator) {
 		}}
 		
 		if line.BreakAfter {
-			keepGoing := iterator (index, '\n', fixed.Point26_6 {
+			keepGoing := iterator(index, '\n', fixed.Point26_6 {
 				X: lastCharRightBound,
 				Y: line.Y,
 			})
 			if !keepGoing { return }
 			index ++
+			lastCharRightBound = fixed.Int26_6(0)
 		}
 	}
 	
-	keepGoing := iterator (index, '\000', fixed.Point26_6 {
-		X: lastCharRightBound,
-		Y: lastLineY,
-	})
-	if !keepGoing { return }
-	index ++
+	if fakeNull {
+		keepGoing := iterator (index, '\000', fixed.Point26_6 {
+			X: lastCharRightBound,
+			Y: lastLineY,
+		})
+		if !keepGoing { return }
+		index ++
+	}
 }
 
 // AtPosition returns the index of the rune at the specified position.
@@ -303,10 +395,10 @@ func (setter *TypeSetter) MinimumSize () image.Point {
 	return image.Pt(width.Round(), height.Round())
 }
 
-// ReccomendedHeightFor returns the reccomended max height if the text were to
-// have its maximum width set to the given width. This does not alter the
+// RecommendedHeight returns the reccomended max height if the text were to have
+// its maximum width set to the given width. This does not alter the
 // typesetter's state.
-func (setter *TypeSetter) ReccomendedHeightFor (width int) (height int) {
+func (setter *TypeSetter) RecommendedHeight (width int) (height int) {
 	setter.needLayout()
 	
 	if setter.lines == nil { return }