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1234
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1 {.emit: "#define STBTT_STATIC".}
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2 {.emit: "#define STB_TRUETYPE_IMPLEMENTATION".}
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3 {.emit: "#include \"" & currentSourcePath.parentDir() & "/stb_truetype.h\"".}
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4
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5 type stbtt_fontinfo {.importc, incompleteStruct.} = object
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6
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7 proc stbtt_InitFont(info: ptr stbtt_fontinfo, data: ptr char, offset: cint): cint {.importc, nodecl.}
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8 proc stbtt_ScaleForPixelHeight(info: ptr stbtt_fontinfo, pixels: cfloat): cfloat {.importc, nodecl.}
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9
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10 proc stbtt_GetCodepointBitmap(info: ptr stbtt_fontinfo, scale_x: cfloat, scale_y: cfloat, codepoint: cint, width, height, xoff, yoff: ptr cint): cstring {.importc, nodecl.}
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11 # proc stbtt_GetCodepointBitmapBox(info: ptr stbtt_fontinfo, codepoint: cint, scale_x, scale_y: cfloat, ix0, iy0, ix1, iy1: ptr cint) {.importc, nodecl.}
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12
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13 proc stbtt_GetCodepointHMetrics(info: ptr stbtt_fontinfo, codepoint: cint, advance, leftBearing: ptr cint) {.importc, nodecl.}
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14 proc stbtt_GetCodepointKernAdvance(info: ptr stbtt_fontinfo, ch1, ch2: cint): cint {.importc, nodecl.}
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15 proc stbtt_FindGlyphIndex(info: ptr stbtt_fontinfo, codepoint: cint): cint {.importc, nodecl.}
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16
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17 proc stbtt_GetFontVMetrics(info: ptr stbtt_fontinfo, ascent, descent, lineGap: ptr cint) {.importc, nodecl.}
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18
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19 proc ReadTrueType*(stream: Stream, name: string, codePoints: seq[Rune], lineHeightPixels: float32): Font =
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20 var
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21 indata = stream.readAll()
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22 fontinfo: stbtt_fontinfo
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23 if stbtt_InitFont(addr fontinfo, addr indata[0], 0) == 0:
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24 raise newException(Exception, "An error occured while loading PNG file")
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25
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26 result.name = name
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27 result.fontscale = float32(stbtt_ScaleForPixelHeight(addr fontinfo, cfloat(lineHeightPixels)))
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28
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29 var ascent, descent, lineGap: cint
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30 stbtt_GetFontVMetrics(addr fontinfo, addr ascent, addr descent, addr lineGap)
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31
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32 result.lineHeight = float32(ascent - descent) * result.fontscale
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33 result.lineAdvance = float32(ascent - descent + lineGap) * result.fontscale
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34
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35 # ensure all codepoints are available in the font
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36 for codePoint in codePoints:
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37 if stbtt_FindGlyphIndex(addr fontinfo, cint(codePoint)) == 0:
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38 warn &"Loading font {name}: Codepoint '{codePoint}' ({cint(codePoint)}) has no glyph"
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39
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40 var
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41 topOffsets: Table[Rune, int]
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42 images: seq[Image[Gray]]
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43 let empty_image = Image[Gray](width: 1, height: 1, data: @[[0'u8]])
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44
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45 for codePoint in codePoints:
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46 var
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47 width, height: cint
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48 offX, offY: cint
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49 let
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50 data = stbtt_GetCodepointBitmap(
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51 addr fontinfo,
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52 result.fontscale,
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53 result.fontscale,
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54 cint(codePoint),
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55 addr width, addr height,
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56 addr offX, addr offY
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57 )
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58 topOffsets[codePoint] = offY
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59
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60 if char(codePoint) in UppercaseLetters:
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61 result.capHeight = float32(height)
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62 if codePoint == Rune('x'):
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63 result.xHeight = float32(height)
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64
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65 if width > 0 and height > 0:
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66 var bitmap = newSeq[Gray](width * height)
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67 for i in 0 ..< width * height:
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68 bitmap[i] = [data[i].uint8]
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69 images.add Image[Gray](width: width.uint32, height: height.uint32, data: bitmap)
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70 else:
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71 images.add empty_image
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72
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73 nativeFree(data)
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74
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75 let packed = Pack(images)
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76
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77 result.fontAtlas = packed.atlas
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78
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79 let w = float32(packed.atlas.width)
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80 let h = float32(packed.atlas.height)
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81 for i in 0 ..< codePoints.len:
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82 let
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83 codePoint = codePoints[i]
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84 image = images[i]
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85 coord = (x: float32(packed.coords[i].x), y: float32(packed.coords[i].y))
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86 iw = float32(image.width)
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87 ih = float32(image.height)
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88 # horizontal spaces:
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89 var advance, leftBearing: cint
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90 stbtt_GetCodepointHMetrics(addr fontinfo, cint(codePoint), addr advance, addr leftBearing)
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91
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92 result.glyphs[codePoint] = GlyphInfo(
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93 dimension: NewVec2f(float32(image.width), float32(image.height)),
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94 uvs: [
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95 NewVec2f((coord.x + 0.5) / w, (coord.y + ih - 0.5) / h),
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96 NewVec2f((coord.x + 0.5) / w, (coord.y + 0.5) / h),
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97 NewVec2f((coord.x + iw - 0.5) / w, (coord.y + 0.5) / h),
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98 NewVec2f((coord.x + iw - 0.5) / w, (coord.y + ih - 0.5) / h),
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99 ],
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100 topOffset: float32(topOffsets[codePoint]),
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101 leftOffset: float32(leftBearing) * result.fontscale,
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102 advance: float32(advance) * result.fontscale,
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103 )
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104
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105 for codePointAfter in codePoints:
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106 result.kerning[(codePoint, codePointAfter)] = float32(stbtt_GetCodepointKernAdvance(
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107 addr fontinfo,
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108 cint(codePoint),
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109 cint(codePointAfter)
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110 )) * result.fontscale
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111
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112 func TextWidth*(text: seq[Rune], font: FontObj): float32 =
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113 var currentWidth = 0'f32
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114 var lineWidths: seq[float32]
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115 for i in 0 ..< text.len:
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116 if text[i] == NEWLINE:
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117 lineWidths.add currentWidth
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118 currentWidth = 0'f32
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119 else:
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120 if not (i == text.len - 1 and text[i].isWhiteSpace):
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121 currentWidth += font.glyphs[text[i]].advance
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122 if i < text.len - 1:
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123 currentWidth += font.kerning[(text[i], text[i + 1])]
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124 lineWidths.add currentWidth
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125 return lineWidths.max
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126
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127 func WordWrapped*(text: seq[Rune], font: FontObj, maxWidth: float32): seq[Rune] =
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128 var remaining: seq[seq[Rune]] = @[@[]]
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129 for c in text:
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130 if c == SPACE:
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131 remaining.add newSeq[Rune]()
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132 else:
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133 remaining[^1].add c
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134 remaining.reverse()
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135
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136 var currentLine: seq[Rune]
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137
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138 while remaining.len > 0:
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139 var currentWord = remaining.pop()
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140 assert not (SPACE in currentWord)
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141
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142 if currentWord.len == 0:
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143 currentLine.add SPACE
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144 else:
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145 assert currentWord[^1] != SPACE
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146 # if this is the first word of the line and it is too long we need to
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147 # split by character
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148 if currentLine.len == 0 and (SPACE & currentWord).TextWidth(font) > maxWidth:
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149 var subWord = @[currentWord[0]]
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150 for c in currentWord[1 .. ^1]:
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151 if (subWord & c).TextWidth(font) > maxWidth:
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152 break
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153 subWord.add c
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154 result.add subWord & NEWLINE
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155 remaining.add currentWord[subWord.len .. ^1] # process rest of the word in next iteration
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156 else:
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157 if (currentLine & SPACE & currentWord).TextWidth(font) <= maxWidth:
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158 if currentLine.len == 0:
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159 currentLine = currentWord
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160 else:
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161 currentLine = currentLine & SPACE & currentWord
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162 else:
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163 result.add currentLine & NEWLINE
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164 remaining.add currentWord
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165 currentLine = @[]
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166 if currentLine.len > 0 and currentLine != @[SPACE]:
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167 result.add currentLine
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168
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169 return result
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170
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