package textdraw import "unicode" import "golang.org/x/image/font" import "golang.org/x/image/math/fixed" // Align specifies a text alignment method. type Align int const ( // AlignLeft aligns the start of each line to the beginning point // of each dot. AlignLeft Align = iota AlignRight AlignCenter AlignJustify ) // RuneLayout contains layout information for a single rune relative to its // word. type RuneLayout struct { X fixed.Int26_6 Width fixed.Int26_6 Rune rune } // WordLayout contains layout information for a single word relative to its // line. type WordLayout struct { X fixed.Int26_6 Width fixed.Int26_6 SpaceAfter fixed.Int26_6 Runes []RuneLayout } // DoWord consumes exactly one word from the given string, and produces a word // layout according to the given font. It returns the remaining text as well. func DoWord (text []rune, face font.Face) (word WordLayout, remaining []rune) { remaining = text gettingSpace := false x := fixed.Int26_6(0) lastRune := rune(-1) for _, char := range text { // if we run into a line break, we must break out immediately // because it is not DoWord's job to handle that. if char == '\n' { break } // if we suddenly run into spaces, and then run into a word // again, we must break out immediately. if unicode.IsSpace(char) { gettingSpace = true } else if gettingSpace { break } // apply kerning if lastRune >= 0 { x += face.Kern(lastRune, char) } lastRune = char // consume and process the rune remaining = remaining[1:] _, advance, ok := face.GlyphBounds(char) if !ok { continue } word.Runes = append (word.Runes, RuneLayout { X: x, Width: advance, Rune: char, }) // advance if gettingSpace { word.SpaceAfter += advance } else { word.Width += advance } x += advance } return } // LastRune returns the last rune in the word. func (word WordLayout) LastRune () rune { if word.Runes == nil { return -1 } else { return word.Runes[len(word.Runes) - 1].Rune } } // FirstRune returns the last rune in the word. func (word WordLayout) FirstRune () rune { if word.Runes == nil { return -1 } else { return word.Runes[0].Rune } } // LineLayout contains layout information for a single line. type LineLayout struct { Y fixed.Int26_6 Width fixed.Int26_6 SpaceAfter fixed.Int26_6 Words []WordLayout BreakAfter bool } // DoLine consumes exactly one line from the given string, and produces a line // layout according to the given font. It returns the remaining text as well. If // maxWidth is greater than zero, this function will stop processing words once // the limit is crossed. The word which would have crossed over the limit will // not be processed. func DoLine (text []rune, face font.Face, maxWidth fixed.Int26_6) (line LineLayout, remaining []rune) { remaining = text x := fixed.Int26_6(0) lastRune := rune(-1) lastWord := WordLayout { } for { // process one word word, remainingFromWord := DoWord(remaining, face) // apply kerning and position. yeah, its unlikely that a letter // will have kerning with a whitespace character. but like, what // if, you know? if lastRune >= 0 && word.FirstRune() >= 0 { x += face.Kern(lastRune, word.FirstRune()) } lastRune = word.LastRune() word.X = x x += word.Width // if we have gone over the maximum width, stop processing // words (if maxWidth is even specified) if maxWidth > 0 && x > maxWidth { break } remaining = remainingFromWord // if the word actually has contents, add it if word.Runes != nil { lastWord = word line.Words = append(line.Words, word) } // if we have hit the end of the line, stop processing words if len(remaining) == 0 { break } if remaining[0] == '\n' { line.BreakAfter = true remaining = remaining[1:] break } } // set the line's width. this is subject to be overridden by the // TypeSetter to match the longest line. if maxWidth > 0 { line.Width = maxWidth } else { line.Width = lastWord.X + lastWord.Width line.SpaceAfter = lastWord.SpaceAfter } return } // Align aligns the text in the line according to the specified alignment // method. func (line *LineLayout) Align (align Align) { // TODO }