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Ligatures: Refactor findInternal() for clarity
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@sedwards2009
sedwards2009 committed Jan 21, 2020
1 parent d92928e commit 6f2b8ba
Showing 1 changed file with 27 additions and 123 deletions.
150 changes: 27 additions & 123 deletions packages/extraterm-font-ligatures/src/index.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -104,7 +104,7 @@ class FontImpl implements Font {
};
}

const result = this._fastFindInternal(glyphIds.slice());
const result = this._findInternal(glyphIds.slice());
const finalResult: LigatureData = {
inputGlyphs: glyphIds,
outputGlyphs: result.sequence,
Expand Down Expand Up @@ -134,7 +134,7 @@ class FontImpl implements Font {
glyphIds.push(this._font.charToGlyphIndex(char));
}

const result = this._fastFindInternal(glyphIds);
const result = this._findInternal(glyphIds);
if (this._cache) {
this._cache.set(text, result.ranges);
}
Expand All @@ -144,117 +144,6 @@ class FontImpl implements Font {

private _findInternal(sequence: number[]): { sequence: number[]; ranges: [number, number][]; } {
const ranges: [number, number][] = [];

let nextLookup = this._getNextLookup(sequence, 0);
while (nextLookup.index !== null) {
const lookup = this._lookupTrees[nextLookup.index];
if (lookup.processForward) {
let lastGlyphIndex = nextLookup.last;
for (let i = nextLookup.first; i < lastGlyphIndex; i++) {
const result = walkTree(lookup.tree, sequence, i, i);
if (result) {
let didSubstitute = false;
for (let j = 0; j < result.substitutions.length; j++) {
const sub = result.substitutions[j];
if (sub !== null) {
sequence[i + j] = sub;
didSubstitute = true;
}
}
if (didSubstitute) {
mergeRange(
ranges,
result.contextRange[0] + i,
result.contextRange[1] + i
);

// Substitutions can end up extending the search range
if (i + result.length >= lastGlyphIndex) {
lastGlyphIndex = i + result.length + 1;
}
}
i += result.length - 1;
}
}
} else {
// We don't need to do the lastGlyphIndex tracking here because
// reverse processing isn't allowed to replace more than one
// character at a time.
for (let i = nextLookup.last - 1; i >= nextLookup.first; i--) {
const result = walkTree(lookup.tree, sequence, i, i);
if (result) {
for (let j = 0; j < result.substitutions.length; j++) {
const sub = result.substitutions[j];
if (sub !== null) {
sequence[i + j] = sub;
}
}

mergeRange(
ranges,
result.contextRange[0] + i,
result.contextRange[1] + i
);

i -= result.length - 1;
}
}
}

nextLookup = this._getNextLookup(sequence, nextLookup.index + 1);
}

return { sequence, ranges };
}

/**
* Returns the lookup and glyph range for the first lookup that might
* contain a match.
*
* @param sequence Input glyph sequence
* @param start The first input to try
*/
private _getNextLookup(sequence: number[], start: number): { index: number | null; first: number; last: number; } {
const result: { index: number | null; first: number; last: number; } = {
index: null,
first: Infinity,
last: -1
};
const glyphLookups = this._glyphLookups;

// Loop through each glyph and find the first valid lookup for it
for (let i = 0; i < sequence.length; i++) {
const lookups = glyphLookups.get(sequence[i]);
if (!lookups) {
continue;
}

for (let j = 0; j < lookups.length; j++) {
const lookupIndex = lookups[j];
if (lookupIndex >= start) {
// Update the lookup information if it's the one we're
// storing or earlier than it.
if (result.index === null || lookupIndex <= result.index) {
result.index = lookupIndex;

if (result.first > i) {
result.first = i;
}

result.last = i + 1;
}

break;
}
}
}

return result;
}

private _fastFindInternal(sequence: number[]): { sequence: number[]; ranges: [number, number][]; } {
const ranges: [number, number][] = [];

const orderedLookups = this._findRelevantLookupsForSequence(sequence);
for (let orderedLookupIndex = 0; orderedLookupIndex < orderedLookups.length; orderedLookupIndex++) {
this._applyLookupToSequence(orderedLookups[orderedLookupIndex], sequence, ranges);
Expand All @@ -268,22 +157,37 @@ class FontImpl implements Font {
const glyphLookups = this._glyphLookups;
const currentLookup = this._lookupTrees[currentLookupIndex];

for (let i = 0; i < sequenceLength; i++) {
const currentLookups = glyphLookups.get(sequence[i]);
if (currentLookups == null || currentLookups.indexOf(currentLookupIndex) === -1) {
continue;
if (currentLookup.processForward) {
for (let i = 0; i < sequenceLength; i++) {
const currentLookups = glyphLookups.get(sequence[i]);
if (currentLookups == null || currentLookups.indexOf(currentLookupIndex) === -1) {
continue;
}

const result = walkTree(currentLookup.tree, sequence, i, i);
if (result && this._applySubstitutionsToSequence(sequence, result.substitutions, i)) {
mergeRange(ranges, result.contextRange[0] + i, result.contextRange[1] + i);
i += result.length - 1;
}
}
} else {
for (let i = sequenceLength-1; i >= 0; i--) {
const currentLookups = glyphLookups.get(sequence[i]);
if (currentLookups == null || currentLookups.indexOf(currentLookupIndex) === -1) {
continue;
}

const result = walkTree(currentLookup.tree, sequence, i, i);
if (result && this._applySubstitutionsToSequence(sequence, result.substitutions, i)) {
mergeRange(ranges, result.contextRange[0] + i, result.contextRange[1] + i);
i+= result.length - 1;
const result = walkTree(currentLookup.tree, sequence, i, i);
if (result && this._applySubstitutionsToSequence(sequence, result.substitutions, i)) {
mergeRange(ranges, result.contextRange[0] + i, result.contextRange[1] + i);
i -= result.length - 1;
}
}
}
}

private _findRelevantLookupsForSequence(sequence: number[]): number[] {
// Determine which lookups we should extamine.
// Determine which lookups we should examine.
const glyphLookups = this._glyphLookups;
const sequenceLength = sequence.length;
const seenLookups = new Set<number>();
Expand Down Expand Up @@ -333,7 +237,7 @@ class FontImpl implements Font {
glyphIds.push(glyphIndex);
}

const result = this._fastFindInternal(glyphIds);
const result = this._findInternal(glyphIds);
let i = 0;
for (const range of result.ranges) {
while (i < range[0]) {
Expand Down

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