315 lines
8.3 KiB
Go
315 lines
8.3 KiB
Go
package artist
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// import "fmt"
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import "image"
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import "unicode"
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import "image/draw"
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import "golang.org/x/image/font"
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import "golang.org/x/image/math/fixed"
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import "git.tebibyte.media/sashakoshka/tomo"
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type characterLayout struct {
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x int
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character rune
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}
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type wordLayout struct {
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position image.Point
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width int
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spaceAfter int
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breaksAfter int
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text []characterLayout
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}
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// Align specifies a text alignment method.
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type Align int
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const (
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// AlignLeft aligns the start of each line to the beginning point
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// of each dot.
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AlignLeft Align = iota
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AlignRight
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AlignCenter
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AlignJustify
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)
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// TextDrawer is a struct that is capable of efficient rendering of wrapped
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// text, and calculating text bounds. It avoids doing redundant work
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// automatically.
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type TextDrawer struct {
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text string
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runes []rune
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face font.Face
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width int
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height int
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align Align
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wrap bool
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cut bool
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layout []wordLayout
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layoutClean bool
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layoutBounds image.Rectangle
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}
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// SetText sets the text of the text drawer.
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func (drawer *TextDrawer) SetText (text string) {
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if drawer.text == text { return }
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drawer.text = text
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drawer.runes = []rune(text)
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drawer.layoutClean = false
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}
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// SetFace sets the font face of the text drawer.
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func (drawer *TextDrawer) SetFace (face font.Face) {
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if drawer.face == face { return }
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drawer.face = face
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drawer.layoutClean = false
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}
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// SetMaxWidth sets a maximum width for the text drawer, and recalculates the
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// layout if needed. If zero is given, there will be no width limit and the text
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// will not wrap.
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func (drawer *TextDrawer) SetMaxWidth (width int) {
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if drawer.width == width { return }
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drawer.width = width
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drawer.wrap = width != 0
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drawer.layoutClean = false
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}
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// SetMaxHeight sets a maximum height for the text drawer. Lines that are
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// entirely below this height will not be drawn, and lines that are on the cusp
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// of this maximum height will be clipped at the point that they cross it.
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func (drawer *TextDrawer) SetMaxHeight (height int) {
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if drawer.height == height { return }
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drawer.height = height
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drawer.cut = height != 0
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drawer.layoutClean = false
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}
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// SetAlignment specifies how the drawer should align its text. For this to have
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// an effect, a maximum width must have been set.
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func (drawer *TextDrawer) SetAlignment (align Align) {
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if drawer.align == align { return }
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drawer.align = align
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drawer.layoutClean = false
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}
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// Draw draws the drawer's text onto the specified canvas at the given offset.
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func (drawer *TextDrawer) Draw (
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destination tomo.Canvas,
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source Pattern,
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offset image.Point,
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) (
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updatedRegion image.Rectangle,
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) {
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wrappedSource := WrappedPattern {
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Pattern: source,
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Width: 0,
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Height: 0, // TODO: choose a better width and height
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}
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if !drawer.layoutClean { drawer.recalculate() }
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// TODO: reimplement a version of draw mask that takes in a pattern and
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// only draws to a tomo.Canvas.
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for _, word := range drawer.layout {
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for _, character := range word.text {
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destinationRectangle,
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mask, maskPoint, _, ok := drawer.face.Glyph (
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fixed.P (
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offset.X + word.position.X + character.x,
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offset.Y + word.position.Y),
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character.character)
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if !ok { continue }
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// FIXME: clip destination rectangle if we are on the cusp of
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// the maximum height.
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draw.DrawMask (
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destination,
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destinationRectangle,
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wrappedSource, image.Point { },
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mask, maskPoint,
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draw.Over)
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updatedRegion = updatedRegion.Union(destinationRectangle)
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}}
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return
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}
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// LayoutBounds returns a semantic bounding box for text to be used to determine
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// an offset for drawing. If a maximum width or height has been set, those will
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// be used as the width and height of the bounds respectively. The origin point
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// (0, 0) of the returned bounds will be equivalent to the baseline at the start
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// of the first line. As such, the minimum of the bounds will be negative.
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func (drawer *TextDrawer) LayoutBounds () (bounds image.Rectangle) {
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if !drawer.layoutClean { drawer.recalculate() }
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bounds = drawer.layoutBounds
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return
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}
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// Em returns the width of an emspace.
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func (drawer *TextDrawer) Em () (width fixed.Int26_6) {
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if drawer.face == nil { return }
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width, _ = drawer.face.GlyphAdvance('M')
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return
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}
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// LineHeight returns the height of one line.
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func (drawer *TextDrawer) LineHeight () (height fixed.Int26_6) {
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if drawer.face == nil { return }
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metrics := drawer.face.Metrics()
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height = metrics.Height
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return
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}
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// ReccomendedHeightFor returns the reccomended max height if the text were to
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// have its maximum width set to the given width. This does not alter the
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// drawer's state.
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func (drawer *TextDrawer) ReccomendedHeightFor (width int) (height int) {
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if !drawer.layoutClean { drawer.recalculate() }
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metrics := drawer.face.Metrics()
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dot := fixed.Point26_6 { 0, metrics.Height }
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for _, word := range drawer.layout {
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if word.width + dot.X.Round() > width {
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dot.Y += metrics.Height
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dot.X = 0
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}
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dot.X += fixed.I(word.width + word.spaceAfter)
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if word.breaksAfter > 0 {
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dot.Y += fixed.I(word.breaksAfter).Mul(metrics.Height)
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dot.X = 0
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}
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}
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return dot.Y.Round()
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}
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func (drawer *TextDrawer) recalculate () {
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drawer.layoutClean = true
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drawer.layout = nil
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drawer.layoutBounds = image.Rectangle { }
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if drawer.runes == nil { return }
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if drawer.face == nil { return }
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metrics := drawer.face.Metrics()
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dot := fixed.Point26_6 { 0, 0 }
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index := 0
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horizontalExtent := 0
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previousCharacter := rune(-1)
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for index < len(drawer.runes) {
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word := wordLayout { }
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word.position.X = dot.X.Round()
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word.position.Y = dot.Y.Round()
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// process a word
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currentCharacterX := fixed.Int26_6(0)
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wordWidth := fixed.Int26_6(0)
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for index < len(drawer.runes) && !unicode.IsSpace(drawer.runes[index]) {
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character := drawer.runes[index]
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_, advance, ok := drawer.face.GlyphBounds(character)
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index ++
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if !ok { continue }
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word.text = append(word.text, characterLayout {
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x: currentCharacterX.Round(),
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character: character,
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})
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dot.X += advance
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wordWidth += advance
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currentCharacterX += advance
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if dot.X.Round () > horizontalExtent {
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horizontalExtent = dot.X.Round()
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}
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if previousCharacter >= 0 {
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dot.X += drawer.face.Kern (
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previousCharacter,
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character)
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}
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previousCharacter = character
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}
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word.width = wordWidth.Round()
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// detect if the word that was just processed goes out of
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// bounds, and if it does, wrap it
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if drawer.wrap &&
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word.width + word.position.X > drawer.width &&
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word.position.X > 0 {
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word.position.Y += metrics.Height.Round()
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word.position.X = 0
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dot.Y += metrics.Height
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dot.X = wordWidth
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}
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// skip over whitespace, going onto a new line if there is a
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// newline character
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for index < len(drawer.runes) && unicode.IsSpace(drawer.runes[index]) {
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character := drawer.runes[index]
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if character == '\n' {
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dot.Y += metrics.Height
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dot.X = 0
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word.breaksAfter ++
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previousCharacter = character
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index ++
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} else {
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_, advance, ok := drawer.face.GlyphBounds(character)
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word.spaceAfter = advance.Round()
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index ++
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if !ok { continue }
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dot.X += advance
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if previousCharacter >= 0 {
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dot.X += drawer.face.Kern (
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previousCharacter,
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character)
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}
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previousCharacter = character
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}
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}
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// add the word to the layout
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drawer.layout = append(drawer.layout, word)
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// if there is a set maximum height, and we have crossed it,
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// stop processing more words. and remove any words that have
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// also crossed the line.
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if
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drawer.cut &&
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(dot.Y - metrics.Ascent - metrics.Descent).Round() >
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drawer.height {
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for
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index := len(drawer.layout) - 1;
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index >= 0; index -- {
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if drawer.layout[index].position.Y < dot.Y.Round() {
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break
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}
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drawer.layout = drawer.layout[:index]
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}
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break
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}
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}
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if drawer.wrap {
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drawer.layoutBounds.Max.X = drawer.width
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} else {
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drawer.layoutBounds.Max.X = horizontalExtent
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}
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if drawer.cut {
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drawer.layoutBounds.Min.Y = 0 - metrics.Ascent.Round()
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drawer.layoutBounds.Max.Y = drawer.height - metrics.Ascent.Round()
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} else {
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drawer.layoutBounds.Min.Y = 0 - metrics.Ascent.Round()
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drawer.layoutBounds.Max.Y = dot.Y.Round() + metrics.Descent.Round()
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}
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// TODO:
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// for each line, calculate the bounds as if the words are left aligned,
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// and then at the end of the process go through each line and re-align
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// everything. this will make the process far simpler.
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}
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