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[PATCH] Add fallback for font loading when eval disabled
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In some cases, such as in use with a CSP header, constructing a function with a
string of javascript is not allowed. However, compiling the various commands
that need to be done on the canvas element is faster than interpreting them.
This patch changes the font renderer to instead emit commands that are compiled
by the font loader. If, during compilation, we receive an EvalError, we instead
interpret them.
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@skalnik
skalnik committed Aug 13, 2015
1 parent 18e1a14 commit 341c5e9
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Showing 3 changed files with 83 additions and 34 deletions.
60 changes: 29 additions & 31 deletions src/core/font_renderer.js
View file
Original file line number Diff line number Diff line change
Expand Up @@ -134,16 +134,15 @@ var FontRendererFactory = (function FontRendererFactoryClosure() {
return 0;
}

function compileGlyf(code, js, font) {
function compileGlyf(code, cmds, font) {
function moveTo(x, y) {
js.push('c.moveTo(' + x + ',' + y + ');');
cmds.push({cmd: 'moveTo', args: [x, y]});
}
function lineTo(x, y) {
js.push('c.lineTo(' + x + ',' + y + ');');
cmds.push({cmd: 'lineTo', args: [x, y]});
}
function quadraticCurveTo(xa, ya, x, y) {
js.push('c.quadraticCurveTo(' + xa + ',' + ya + ',' +
x + ',' + y + ');');
cmds.push({cmd: 'quadraticCurveTo', args: [xa, ya, x, y]});
}

var i = 0;
Expand Down Expand Up @@ -189,11 +188,11 @@ var FontRendererFactory = (function FontRendererFactoryClosure() {
}
var subglyph = font.glyphs[glyphIndex];
if (subglyph) {
js.push('c.save();');
js.push('c.transform(' + scaleX + ',' + scale01 + ',' +
scale10 + ',' + scaleY + ',' + x + ',' + y + ');');
compileGlyf(subglyph, js, font);
js.push('c.restore();');
cmds.push({cmd: 'save'});
cmds.push({cmd: 'transform',
args: [scaleX, scale01, scale10, scaleY, x, y]});
compileGlyf(subglyph, cmds, font);
cmds.push({cmd: 'restore'});
}
} while ((flags & 0x20));
} else {
Expand Down Expand Up @@ -289,20 +288,19 @@ var FontRendererFactory = (function FontRendererFactoryClosure() {
}
}

function compileCharString(code, js, font) {
function compileCharString(code, cmds, font) {
var stack = [];
var x = 0, y = 0;
var stems = 0;

function moveTo(x, y) {
js.push('c.moveTo(' + x + ',' + y + ');');
cmds.push({cmd: 'moveTo', args: [x, y]});
}
function lineTo(x, y) {
js.push('c.lineTo(' + x + ',' + y + ');');
cmds.push({cmd: 'lineTo', args: [x, y]});
}
function bezierCurveTo(x1, y1, x2, y2, x, y) {
js.push('c.bezierCurveTo(' + x1 + ',' + y1 + ',' + x2 + ',' + y2 + ',' +
x + ',' + y + ');');
cmds.push({cmd: 'bezierCurveTo', args: [x1, y1, x2, y2, x, y]});
}

function parse(code) {
Expand Down Expand Up @@ -431,16 +429,16 @@ var FontRendererFactory = (function FontRendererFactoryClosure() {
var bchar = stack.pop();
y = stack.pop();
x = stack.pop();
js.push('c.save();');
js.push('c.translate('+ x + ',' + y + ');');
cmds.push({cmd: 'save'});
cmds.push({cmd: 'translate', args: [x, y]});
var gid = lookupCmap(font.cmap, String.fromCharCode(
font.glyphNameMap[Encodings.StandardEncoding[achar]]));
compileCharString(font.glyphs[gid], js, font);
js.push('c.restore();');
compileCharString(font.glyphs[gid], cmds, font);
cmds.push({cmd: 'restore'});

gid = lookupCmap(font.cmap, String.fromCharCode(
font.glyphNameMap[Encodings.StandardEncoding[bchar]]));
compileCharString(font.glyphs[gid], js, font);
compileCharString(font.glyphs[gid], cmds, font);
}
return;
case 18: // hstemhm
Expand Down Expand Up @@ -609,16 +607,16 @@ var FontRendererFactory = (function FontRendererFactoryClosure() {
return noop;
}

var js = [];
js.push('c.save();');
js.push('c.transform(' + this.fontMatrix.join(',') + ');');
js.push('c.scale(size, -size);');
var cmds = [];
cmds.push({cmd: 'save'});
cmds.push({cmd: 'transform', args: this.fontMatrix.slice()});
cmds.push({cmd: 'scale', args: ['size', '-size']});

this.compileGlyphImpl(code, js);
this.compileGlyphImpl(code, cmds);

js.push('c.restore();');
cmds.push({cmd: 'restore'});

return js.join('\n');
return cmds;
},

compileGlyphImpl: function () {
Expand All @@ -642,8 +640,8 @@ var FontRendererFactory = (function FontRendererFactoryClosure() {
}

Util.inherit(TrueTypeCompiled, CompiledFont, {
compileGlyphImpl: function (code, js) {
compileGlyf(code, js, this);
compileGlyphImpl: function (code, cmds) {
compileGlyf(code, cmds, this);
}
});

Expand All @@ -664,8 +662,8 @@ var FontRendererFactory = (function FontRendererFactoryClosure() {
}

Util.inherit(Type2Compiled, CompiledFont, {
compileGlyphImpl: function (code, js) {
compileCharString(code, js, this);
compileGlyphImpl: function (code, cmds) {
compileCharString(code, cmds, this);
}
});

Expand Down
8 changes: 8 additions & 0 deletions src/display/api.js
View file
Original file line number Diff line number Diff line change
Expand Up @@ -177,6 +177,14 @@ PDFJS.openExternalLinksInNewWindow = (
PDFJS.openExternalLinksInNewWindow === undefined ?
false : PDFJS.openExternalLinksInNewWindow);

/**
* Determines if we can eval strings as JS. Primarily used to improve
* performance for font rendering.
* @var {boolean}
*/
PDFJS.isEvalSupported = (PDFJS.isEvalSupported === undefined ?
true : PDFJS.isEvalSupported);

/**
* Document initialization / loading parameters object.
*
Expand Down
49 changes: 46 additions & 3 deletions src/display/font_loader.js
View file
Original file line number Diff line number Diff line change
Expand Up @@ -77,6 +77,18 @@ var FontLoader = {
));
},

get isEvalSupported() {
var evalSupport = false;
if (PDFJS.isEvalSupported) {
try {
/* jshint evil: true */
new Function('');
evalSupport = true;
} catch (e) {}
}
return shadow(this, 'isEvalSupported', evalSupport);
},

loadTestFontId: 0,

loadingContext: {
Expand Down Expand Up @@ -365,9 +377,40 @@ var FontFaceObject = (function FontFaceObjectClosure() {

getPathGenerator: function FontLoader_getPathGenerator(objs, character) {
if (!(character in this.compiledGlyphs)) {
var js = objs.get(this.loadedName + '_path_' + character);
/*jshint -W054 */
this.compiledGlyphs[character] = new Function('c', 'size', js);
var cmds = objs.get(this.loadedName + '_path_' + character);
var current, i, len;

// If we can, compile cmds into JS for MAXIMUM SPEED
if (FontLoader.isEvalSupported) {
var args, js = '';
for (i = 0, len = cmds.length; i < len; i++) {
current = cmds[i];

if (current.args !== undefined) {
args = current.args.join(',');
} else {
args = '';
}

js += 'c.' + current.cmd + '(' + args + ');\n';
}
/* jshint -W054 */
this.compiledGlyphs[character] = new Function('c', 'size', js);
} else {
// But fall back on using Function.prototype.apply() if we're
// blocked from using eval() for whatever reason (like CSP policies)
this.compiledGlyphs[character] = function(c, size) {
for (i = 0, len = cmds.length; i < len; i++) {
current = cmds[i];

if (current.cmd === 'scale') {
current.args = [size, -size];
}

c[current.cmd].apply(c, current.args);
}
};
}
}
return this.compiledGlyphs[character];
}
Expand Down

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