1- // stb_truetype.h - v1.25 - public domain
1+ // stb_truetype.h - v1.26 - public domain
22// authored from 2009-2021 by Sean Barrett / RAD Game Tools
33//
44// =======================================================================
5858//
5959// VERSION HISTORY
6060//
61+ // 1.26 (2021-08-28) fix broken rasterizer
6162// 1.25 (2021-07-11) many fixes
6263// 1.24 (2020-02-05) fix warning
6364// 1.23 (2020-02-02) query SVG data for glyphs; query whole kerning table (but only kern not GPOS)
@@ -3061,6 +3062,23 @@ static void stbtt__handle_clipped_edge(float *scanline, int x, stbtt__active_edg
30613062 }
30623063}
30633064
3065+ static float stbtt__sized_trapezoid_area (float height , float top_width , float bottom_width )
3066+ {
3067+ STBTT_assert (top_width >= 0 );
3068+ STBTT_assert (bottom_width >= 0 );
3069+ return (top_width + bottom_width ) / 2.0f * height ;
3070+ }
3071+
3072+ static float stbtt__position_trapezoid_area (float height , float tx0 , float tx1 , float bx0 , float bx1 )
3073+ {
3074+ return stbtt__sized_trapezoid_area (height , tx1 - tx0 , bx1 - bx0 );
3075+ }
3076+
3077+ static float stbtt__sized_triangle_area (float height , float width )
3078+ {
3079+ return height * width / 2 ;
3080+ }
3081+
30643082static void stbtt__fill_active_edges_new (float * scanline , float * scanline_fill , int len , stbtt__active_edge * e , float y_top )
30653083{
30663084 float y_bottom = y_top + 1 ;
@@ -3115,10 +3133,10 @@ static void stbtt__fill_active_edges_new(float *scanline, float *scanline_fill,
31153133 float height ;
31163134 // simple case, only spans one pixel
31173135 int x = (int ) x_top ;
3118- height = sy1 - sy0 ;
3136+ height = ( sy1 - sy0 ) * e -> direction ;
31193137 STBTT_assert (x >= 0 && x < len );
3120- scanline [x ] += e -> direction * ( 1 - (( x_top - x ) + ( x_bottom - x ))/ 2 ) * height ;
3121- scanline_fill [x ] += e -> direction * height ; // everything right of this pixel is filled
3138+ scanline [x ] += stbtt__position_trapezoid_area ( height , x_top , x + 1.0f , x_bottom , x + 1.0f ) ;
3139+ scanline_fill [x ] += height ; // everything right of this pixel is filled
31223140 } else {
31233141 int x ,x1 ,x2 ;
31243142 float y_crossing , y_final , step , sign , area ;
@@ -3134,47 +3152,89 @@ static void stbtt__fill_active_edges_new(float *scanline, float *scanline_fill,
31343152 dy = - dy ;
31353153 t = x0 , x0 = xb , xb = t ;
31363154 }
3137- assert (dy >= 0 );
3138- assert (dx >= 0 );
3155+ STBTT_assert (dy >= 0 );
3156+ STBTT_assert (dx >= 0 );
31393157
31403158 x1 = (int ) x_top ;
31413159 x2 = (int ) x_bottom ;
31423160 // compute intersection with y axis at x1+1
3143- y_crossing = (x1 + 1 - x0 ) * dy + y_top ;
3161+ y_crossing = y_top + dy * (x1 + 1 - x0 );
3162+
3163+ // compute intersection with y axis at x2
3164+ y_final = y_top + dy * (x2 - x0 );
3165+
3166+ // x1 x_top x2 x_bottom
3167+ // y_top +------|-----+------------+------------+--------|---+------------+
3168+ // | | | | | |
3169+ // | | | | | |
3170+ // sy0 | Txxxxx|............|............|............|............|
3171+ // y_crossing | *xxxxx.......|............|............|............|
3172+ // | | xxxxx..|............|............|............|
3173+ // | | /- xx*xxxx........|............|............|
3174+ // | | dy < | xxxxxx..|............|............|
3175+ // y_final | | \- | xx*xxx.........|............|
3176+ // sy1 | | | | xxxxxB...|............|
3177+ // | | | | | |
3178+ // | | | | | |
3179+ // y_bottom +------------+------------+------------+------------+------------+
3180+ //
3181+ // goal is to measure the area covered by '.' in each pixel
3182+
31443183 // if x2 is right at the right edge of x1, y_crossing can blow up, github #1057
3184+ // @TODO: maybe test against sy1 rather than y_bottom?
31453185 if (y_crossing > y_bottom )
31463186 y_crossing = y_bottom ;
31473187
31483188 sign = e -> direction ;
3149- // area of the rectangle covered from y0..y_crossing
3189+
3190+ // area of the rectangle covered from sy0..y_crossing
31503191 area = sign * (y_crossing - sy0 );
3151- // area of the triangle (x_top,y0), (x+1,y0), (x+1,y_crossing)
3152- scanline [x1 ] += area * (x1 + 1 - x_top )/2 ;
3192+
3193+ // area of the triangle (x_top,sy0), (x1+1,sy0), (x1+1,y_crossing)
3194+ scanline [x1 ] += stbtt__sized_triangle_area (area , x1 + 1 - x_top );
31533195
31543196 // check if final y_crossing is blown up; no test case for this
3155- y_final = y_crossing + dy * (x2 - (x1 + 1 )); // advance y by number of steps taken below
31563197 if (y_final > y_bottom ) {
31573198 y_final = y_bottom ;
31583199 dy = (y_final - y_crossing ) / (x2 - (x1 + 1 )); // if denom=0, y_final = y_crossing, so y_final <= y_bottom
31593200 }
31603201
3161- step = sign * dy * 1 ; // dy is dy/dx, change in y for every 1 change in x, which is also how much pixel area changes for each step in x
3202+ // in second pixel, area covered by line segment found in first pixel
3203+ // is always a rectangle 1 wide * the height of that line segment; this
3204+ // is exactly what the variable 'area' stores. it also gets a contribution
3205+ // from the line segment within it. the THIRD pixel will get the first
3206+ // pixel's rectangle contribution, the second pixel's rectangle contribution,
3207+ // and its own contribution. the 'own contribution' is the same in every pixel except
3208+ // the leftmost and rightmost, a trapezoid that slides down in each pixel.
3209+ // the second pixel's contribution to the third pixel will be the
3210+ // rectangle 1 wide times the height change in the second pixel, which is dy.
3211+
3212+ step = sign * dy * 1 ; // dy is dy/dx, change in y for every 1 change in x,
3213+ // which multiplied by 1-pixel-width is how much pixel area changes for each step in x
3214+ // so the area advances by 'step' every time
3215+
31623216 for (x = x1 + 1 ; x < x2 ; ++ x ) {
3163- scanline [x ] += area + step /2 ; // area of parallelogram is step/2
3217+ scanline [x ] += area + step /2 ; // area of trapezoid is 1* step/2
31643218 area += step ;
31653219 }
31663220 STBTT_assert (STBTT_fabs (area ) <= 1.01f ); // accumulated error from area += step unless we round step down
3221+ STBTT_assert (sy1 > y_final - 0.01f );
31673222
3168- // area of the triangle (x2,y_crossing), (x_bottom,y1), (x2,y1)
3169- scanline [x2 ] += area + sign * (x_bottom - x2 )/2 * (sy1 - y_crossing );
3223+ // area covered in the last pixel is the rectangle from all the pixels to the left,
3224+ // plus the trapezoid filled by the line segment in this pixel all the way to the right edge
3225+ scanline [x2 ] += area + sign * stbtt__position_trapezoid_area (sy1 - y_final , (float ) x2 , x2 + 1.0f , x_bottom , x2 + 1.0f );
31703226
3227+ // the rest of the line is filled based on the total height of the line segment in this pixel
31713228 scanline_fill [x2 ] += sign * (sy1 - sy0 );
31723229 }
31733230 } else {
31743231 // if edge goes outside of box we're drawing, we require
31753232 // clipping logic. since this does not match the intended use
31763233 // of this library, we use a different, very slow brute
31773234 // force implementation
3235+ // note though that this does happen some of the time because
3236+ // x_top and x_bottom can be extrapolated at the top & bottom of
3237+ // the shape and actually lie outside the bounding box
31783238 int x ;
31793239 for (x = 0 ; x < len ; ++ x ) {
31803240 // cases:
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