drivers/video/stb_truetype.h

2 // authored from 2009-2021 by Sean Barrett / RAD Game Tools
150 //         Characters are defined by unicode codepoints, e.g. 65 is
199 //    a scale factor SF that will be used by all other functions.
422 ////   of C library functions used by stb_truetype, e.g. if you don't
613 // as computed by stbtt_ScaleForPixelHeight. To use a point size as computed
614 // by stbtt_ScaleForMappingEmToPixels, wrap the point size in STBTT_POINT_SIZE()
636 // Oversampling a font increases the quality by allowing higher-quality subpixel
641 // pack context. The default (no oversampling) is achieved by h_oversample=1
655 // typically an empty box by convention.
764 // so if you prefer to measure height by the ascent only, use a similar calculation.
775 // so you should advance the vertical position by "*ascent - *descent + *lineGap"
776 //   these are expressed in unscaled coordinates, so you must multiply by
813 // Retrieves a complete list of all of the kerning pairs provided by the font
815 // The table will be sorted by (a.glyph1 == b.glyph1)?(a.glyph2 < b.glyph2):(a.glyph1 < b.glyph1)
959 //        pixel_dist_scale  --  what value the SDF should increase by when moving one SDF "pixel" away from the edge (on the 0..255 scale)
988 // The function computes the SDF analytically at each SDF pixel, not by e.g.
2848    z->x = STBTT_ifloor(STBTT_FIX * e->x0 + z->dx * (start_point - e->y0)); // use z->dx so when we offset later it's by the same amount
3181                // goal is to measure the area covered by '.' in each pixel
3202                // in second pixel, area covered by line segment found in first pixel
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
3224                // plus the trapezoid filled by the line segment in this pixel all the way to the right edge
3243                // with left or right edges can be handled by splitting into two (or three)
3537    // now sort the edges by their highest point (should snap to integer, and then by x)
4142    // which shifts phase by (oversample - 1)/2 pixels in
4500          int by = STBTT_max(y0,STBTT_max(y1,y2));
4501          if (y > ay && y < by && x > ax) {
4624             float bx = x0 - 2*x1 + x2, by = y0 - 2*y1 + y2;
4625             float len2 = bx*bx + by*by;
4627                precompute[i] = 1.0f / (bx*bx + by*by);
4683                      float bx = x0 - 2*x1 + x2, by = y0 - 2*y1 + y2;
4689                         float a = 3*(ax*bx + ay*by);
4690                         float b = 2*(ax*ax + ay*ay) + (mx*bx+my*by);
4708                         float b = 3*(ax*bx + ay*by) * a_inv; // could precompute this as it doesn't depend on sample point
4709                         float c = (2*(ax*ax + ay*ay) + (mx*bx+my*by)) * a_inv;
5063 commercial or non-commercial, and by any means.