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[api-minor] Prevent Font.exportData from exporting internal/unused properties

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A number of *internal* font properties, which only make sense on the worker-thread, were previously exported. Some of these properties could also contain potentially large Arrays/Objects, which thus unnecessarily increases memory usage since we're forced to copy these to the main-thread and also store them there.

This patch stops exporting the following font properties:

 - "_shadowWidth": An internal property, which was never intended to be exported.

 - "charsCache": An internal cache, which was never intended to be exported and doesn't make any sense on the main-thread. Furthermore, by the time `Font.exportData` is called it's usually `undefined` or a mostly empty Object as well.

 - "cidEncoding": An internal property used with (some) composite fonts.
   As can be seen in the `PartialEvaluator.translateFont` method, `cidEncoding` will only be assigned a value when the font dictionary has an "Encoding" entry which is a `Name` (and not in the `Stream` case, since those obviously cannot be cloned).
   All-in-all this property doesn't really make sense on the main-thread and/or in the API, and note also that the resulting `cMap` property is (partially) available already.

 - "fallbackToUnicode": An internal map, part of the heuristics used to improve text-selection in (some) badly generated PDF documents with simple fonts. This was never intended to be exposed on the main-thread and/or in the API.

 - "glyphCache": An internal cache, which was never intended to be exported and which doesn't make any sense on the main-thread. Furthermore, by the time `Font.exportData` is called it's usually a mostly empty Object as well.

 - "isOpenType": An internal property, used only during font parsing on the worker-thread. In the *very* unlikely event that an API consumer actually needs that information, then `fontType` should be a (generally) much better property to use.

Finally, in the (hopefully) unlikely event that any of these properties become necessary on the main-thread, re-adding them to the white-list is easy to do.
This commit is contained in:
Jonas Jenwald 2020-03-30 13:19:36 +02:00
parent 664f7de540
commit a5e4cccf13
1 changed files with 0 additions and 6 deletions
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6
src/core/fonts.js
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@ -88,15 +88,12 @@ var PDF_GLYPH_SPACE_UNITS = 1000;
var SEAC_ANALYSIS_ENABLED = true;
const EXPORT_DATA_PROPERTIES = [
"_shadowWidth",
"ascent",
"bbox",
"black",
"bold",
"cMap",
"charProcOperatorList",
"charsCache",
"cidEncoding",
"composite",
"data",
"defaultEncoding",
@ -105,12 +102,9 @@ const EXPORT_DATA_PROPERTIES = [
"descent",
"differences",
"fallbackName",
"fallbackToUnicode",
"fontMatrix",
"fontType",
"glyphCache",
"isMonospace",
"isOpenType",
"isSerifFont",
"isSymbolicFont",
"isType3Font",