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Add support for \{,d,t}binom

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Test Plan: `\binom xy^{\binom xy^{\binom xy}}` looks like something. `\dbinom` and `\tbinom` also seem to work.

Reviewers: emily

Reviewed By: emily

Subscribers: jessie

Differential Revision: http://phabricator.khanacademy.org/D13315
This commit is contained in:
Ben Alpert
2014-10-14 17:01:19 -07:00
parent 10e9b4ec12
commit 006a0a761c
6 changed files with 171 additions and 47 deletions
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138
src/buildTree.js
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@@ -364,14 +364,14 @@ var groupTypes = {
[base, supsub]);
},
frac: function(group, options, prev) {
genfrac: function(group, options, prev) {
// Fractions are handled in the TeXbook on pages 444-445, rules 15(a-e).
// Figure out what style this fraction should be in based on the
// function used
var fstyle = options.style;
if (group.value.size === "dfrac") {
if (group.value.size === "display") {
fstyle = Style.DISPLAY;
} else if (group.value.size === "tfrac") {
} else if (group.value.size === "text") {
fstyle = Style.TEXT;
}
@@ -384,60 +384,118 @@ var groupTypes = {
var denom = buildGroup(group.value.denom, options.withStyle(dstyle));
var denomreset = makeSpan([fstyle.reset(), dstyle.cls()], [denom]);
var ruleWidth = fontMetrics.metrics.defaultRuleThickness /
options.style.sizeMultiplier;
var ruleWidth;
if (group.value.hasBarLine) {
ruleWidth = fontMetrics.metrics.defaultRuleThickness /
options.style.sizeMultiplier;
} else {
ruleWidth = 0;
}
var mid = makeSpan(
[options.style.reset(), Style.TEXT.cls(), "frac-line"]);
// Manually set the height of the line because its height is created in
// CSS
mid.height = ruleWidth;
// Rule 15b, 15d
var numShift, denomShift, clearance;
// Rule 15b
var numShift;
var clearance;
var denomShift;
if (fstyle.size === Style.DISPLAY.size) {
numShift = fontMetrics.metrics.num1;
if (ruleWidth > 0) {
clearance = 3 * ruleWidth;
} else {
clearance = 7 * fontMetrics.metrics.defaultRuleThickness;
}
denomShift = fontMetrics.metrics.denom1;
clearance = 3 * ruleWidth;
} else {
numShift = fontMetrics.metrics.num2;
if (ruleWidth > 0) {
numShift = fontMetrics.metrics.num2;
clearance = ruleWidth;
} else {
numShift = fontMetrics.metrics.num3;
clearance = 3 * fontMetrics.metrics.defaultRuleThickness;
}
denomShift = fontMetrics.metrics.denom2;
clearance = ruleWidth;
}
var axisHeight = fontMetrics.metrics.axisHeight;
var frac;
if (ruleWidth === 0) {
// Rule 15c
var candiateClearance =
(numShift - numer.depth) - (denom.height - denomShift);
if (candiateClearance < clearance) {
numShift += 0.5 * (clearance - candiateClearance);
denomShift += 0.5 * (clearance - candiateClearance);
}
// Rule 15d
if ((numShift - numer.depth) - (axisHeight + 0.5 * ruleWidth)
< clearance) {
numShift +=
clearance - ((numShift - numer.depth) -
(axisHeight + 0.5 * ruleWidth));
frac = buildCommon.makeVList([
{type: "elem", elem: denomreset, shift: denomShift},
{type: "elem", elem: numerreset, shift: -numShift}
], "individualShift", null, options);
} else {
// Rule 15d
var axisHeight = fontMetrics.metrics.axisHeight;
if ((numShift - numer.depth) - (axisHeight + 0.5 * ruleWidth)
< clearance) {
numShift +=
clearance - ((numShift - numer.depth) -
(axisHeight + 0.5 * ruleWidth));
}
if ((axisHeight - 0.5 * ruleWidth) - (denom.height - denomShift)
< clearance) {
denomShift +=
clearance - ((axisHeight - 0.5 * ruleWidth) -
(denom.height - denomShift));
}
var mid = makeSpan(
[options.style.reset(), Style.TEXT.cls(), "frac-line"]);
// Manually set the height of the line because its height is
// created in CSS
mid.height = ruleWidth;
var midShift = -(axisHeight - 0.5 * ruleWidth);
frac = buildCommon.makeVList([
{type: "elem", elem: denomreset, shift: denomShift},
{type: "elem", elem: mid, shift: midShift},
{type: "elem", elem: numerreset, shift: -numShift}
], "individualShift", null, options);
}
if ((axisHeight - 0.5 * ruleWidth) - (denom.height - denomShift)
< clearance) {
denomShift +=
clearance - ((axisHeight - 0.5 * ruleWidth) -
(denom.height - denomShift));
}
var midShift = -(axisHeight - 0.5 * ruleWidth);
var frac = buildCommon.makeVList([
{type: "elem", elem: denomreset, shift: denomShift},
{type: "elem", elem: mid, shift: midShift},
{type: "elem", elem: numerreset, shift: -numShift}
], "individualShift", null, options);
// Since we manually change the style sometimes (with \dfrac or \tfrac),
// account for the possible size change here.
frac.height *= fstyle.sizeMultiplier / options.style.sizeMultiplier;
frac.depth *= fstyle.sizeMultiplier / options.style.sizeMultiplier;
// Rule 15e
var innerChildren = [makeSpan(["mfrac"], [frac])];
var delimSize;
if (fstyle.size === Style.DISPLAY.size) {
delimSize = fontMetrics.metrics.delim1;
} else {
delimSize = fontMetrics.metrics.getDelim2(fstyle);
}
if (group.value.leftDelim != null) {
innerChildren.unshift(
delimiter.customSizedDelim(
group.value.leftDelim, delimSize, true,
options.withStyle(fstyle), group.mode)
);
}
if (group.value.rightDelim != null) {
innerChildren.push(
delimiter.customSizedDelim(
group.value.rightDelim, delimSize, true,
options.withStyle(fstyle), group.mode)
);
}
return makeSpan(
["minner", "mfrac", options.style.reset(), fstyle.cls()],
[frac], options.getColor());
["minner", options.style.reset(), fstyle.cls()],
innerChildren,
options.getColor());
},
spacing: function(group, options, prev) {