Support stretchy wide elements. (#670)

2025-10-12 06:28:40 +00:00 · 2017-06-15 20:47:51 -07:00
parent eaa7f3a17d
commit eff7653c51
57 changed files with 1634 additions and 42 deletions
--- a/static/images/Image-Licensing-and-Technical-Notes.txt
+++ b/static/images/Image-Licensing-and-Technical-Notes.txt
@@ -0,0 +1,70 @@
+Copyright and Licensing
+=======================
+
+Many KaTeX SVG images have been adapted from glyphs in the KaTeX fonts.
+Copyright (c) 2009-2010, Design Science, Inc. (<www.mathjax.org>)
+Copyright (c) 2014-2017 Khan Academy (<www.khanacademy.org>)
+Licensed under the SIL Open Font License, Version 1.1. See \nhttp://scripts.sil.org/OFL
+
+The license terms above apply to the following images:
+          FILENAME         ORIGINAL GLYPH     ORIGINAL FONT FILE
+    =====================  ==============     ==================
+    doubleleftarrow.svg       U+21D0             KaTeX Main
+    doubleleftrightarrow.svg  U+21D4             KaTeX Main
+    doublerightarrow.svg      U+21D2             KaTeX Main
+    hookleftarrow.svg         U+21A9             KaTeX Main
+    hookrightarrow.svg        U+21AA             KaTeX Main
+    leftarrow.svg             U+2190             KaTeX Main
+    leftharpoon.svg           U+21BD             KaTeX Main
+    leftrightarrow.svg        U+2194             KaTeX Main
+    leftrightharpoons.svg     U+21BC/21B1        KaTeX Main
+    mapsto.svg                U+21A6             KaTeX Main
+    overbrace.svg             U+23A9/23A8/23A7   KaTeX Size 4 Regular
+    rightarrow.svg            U+2192             KaTeX Main
+    rightharpoon.svg          U+21C0             KaTeX Main
+    rightharpoondown.svg      U+21C1             KaTeX Main
+    rightleftharpoons.svg     U+21CC             KaTeX Main
+    tofrom.svg                U+21C4             KaTeX AMS Regular
+    twoheadleftarrow.svg      U+219E             KaTeX AMS Regular
+    twoheadrightarrow.svg     U+21A0             KaTeX AMS Regular
+    underbrace.svg            U+23A9/23A8/23A7   KaTeX Size 4 Regular
+
+Images for \widehat, \widetilde, \overgroup, and \undergroup have been adapted (and modified)
+from font glyphs in the MnSymbol package. These fonts are in the public domain.
+
+
+Technical Comments
+==================
+
+Nested SVGs
+    Many of the KaTeX SVG images contain a nested SVG. This is done to achieve a
+    stretchy image while avoiding distortion of arrowheads or brace corners.
+
+    The inner SVG typically contains a very long (400 em) arrow.
+
+    The outer SVG acts like a window that exposes only part of the inner SVG. The
+    outer SVG will grow or shrink to match the dimensions set for it by CSS.
+
+    The inner SVG always has a longer, thinner aspect ratio than the outer SVG.
+    After the inner SVG fills 100% of the height of the outer SVG, there is a long
+    arrow shaft left over. That left-over shaft is not shown. Instead, it is
+    sliced off because the inner SVG is set to "preserveAspectRatio='... slice'".
+
+    Thus, the reader sees an arrow that matches the subject matter width without
+    distortion.
+
+    Some functions, such as \cancel, need to vary their aspect ratio. These functions
+    do not get the nested SVG treatment.
+
+Second Brush Stroke
+    Low resolution monitors struggle to display images in fine detail.
+    So browsers apply anti-aliasing as described at http://www.rastertragedy.com/.
+    A long straight arrow shaft therefore will sometimes appear as if it has a
+    blurred edge.
+
+    To mitigate this, these SVG files contain a second "brush-stroke" on the
+    arrow shafts. That is, a second long thin rectangular SVG path has been
+    written directly on top of each arrow shaft. This reinforcement causes some
+    of the screen pixels to display as black instead of the anti-aliased gray
+    pixel that a  single path would generate. So we get arrow shafts whose
+    edges appear to be sharper.