Add explanatory comment

mapbox · Jun 7, 2017 · 0997e07 · 0997e07
1 parent 59075d2
commit 0997e07
Showing 1 changed file with 4 additions and 0 deletions.
diff --git a/src/symbol/quads.js b/src/symbol/quads.js
@@ -193,6 +193,10 @@ function getGlyphQuads(anchor, shaping, boxScale, line, layer, alongLine, global
 
  const baseQuad = {
  upright: calculateBaseQuad(positionedGlyph, glyph, rect, textOffset),
+ // The quad coordinates represent an offset from the anchor. Since
+ // we use the same anchor for both the 'upright' and 'upside-down'
+ // copies of each glyph, invert the y dimension of text-offset for the
+ // upside-down case.
  upsideDown: calculateBaseQuad(positionedGlyph, glyph, rect, [textOffset[0], -textOffset[1]])
  };