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Possible performance improvements #238

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Possible performance improvements #238

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41 changes: 41 additions & 0 deletions src/SVGTree.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,7 @@
#include <algorithm>
#include <array>
#include <cstring>
#include <iostream>
#include <sstream>
#include "BoundingBox.hpp"
#include "DVIToSVG.hpp"
Expand Down Expand Up @@ -158,13 +159,45 @@ void SVGTree::transformPage (const Matrix &usermatrix) {
_page->setTransform(usermatrix);
}

class GlyphNodeParams {
public:
const int c;
const PhysicalFont *font;
GFGlyphTracer::Callback *cb;
bool USE_FONTS;
};

bool operator==(const GlyphNodeParams &a, const GlyphNodeParams &b) {
return a.c == b.c && a.font == b.font && a.cb == b.cb && a.USE_FONTS == b.USE_FONTS;
}
template <>
struct std::hash<GlyphNodeParams> {
std::size_t operator()(GlyphNodeParams const &p) const noexcept {
// based on https://en.cppreference.com/w/cpp/utility/hash#Example
// I don't *really* know what I'm doing
return std::hash<int>{}(p.c) ^
(std::hash<const void *>{}(p.font) << 1) ^
(std::hash<void *>{}(p.cb) << 2) ^
(std::hash<bool>{}(p.USE_FONTS) << 3);
}
};

std::unordered_map<GlyphNodeParams, unique_ptr<XMLElement>> glyphNodeCache = {};

/** Creates an SVG element for a single glyph.
* @param[in] c character number
* @param[in] font font to extract the glyph from
* @param[in] cb pointer to callback object for sending feedback to the glyph tracer (may be 0)
* @return pointer to element node if glyph exists, 0 otherwise */
static unique_ptr<XMLElement> createGlyphNode (int c, const PhysicalFont &font, GFGlyphTracer::Callback *cb) {

GlyphNodeParams params = {c, &font, cb, SVGTree::USE_FONTS};
if (glyphNodeCache.count(params) > 0) {
std::cout << "cached!" << std::endl;
return util::static_unique_ptr_cast<XMLElement>(glyphNodeCache[params]->clone());

}

Glyph glyph;
if (!font.getGlyph(c, glyph, cb) || (!SVGTree::USE_FONTS && !SVGTree::CREATE_USE_ELEMENTS))
return nullptr;
Expand All @@ -191,6 +224,14 @@ static unique_ptr<XMLElement> createGlyphNode (int c, const PhysicalFont &font,
ostringstream oss;
glyph.writeSVG(oss, SVGTree::RELATIVE_PATH_CMDS, sx, sy);
glyphNode->addAttribute("d", oss.str());

// TODO this cache strategy is crude but better than nothing
if (glyphNodeCache.size() > 1<<14) {
glyphNodeCache.clear();
}
glyphNodeCache[params] = util::static_unique_ptr_cast<XMLElement>(glyphNode->clone());
std::cout << "size of cache: " << glyphNodeCache.size() << std::endl;

return glyphNode;
}

Expand Down