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Add global caching, for /Resources without blend modes, and use it to reduce repeated fetching/parsing in PartialEvaluator.hasBlendModes

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The `PartialEvaluator.hasBlendModes` method is necessary to determine if there's any blend modes on a page, which unfortunately requires *synchronous* parsing of the /Resources of each page before its rendering can start (see the "StartRenderPage"-message).
In practice it's not uncommon for certain /Resources-entries to be found on more than one page (referenced via the XRef-table), which thus leads to unnecessary re-fetching/re-parsing of data in `PartialEvaluator.hasBlendModes`.

To improve performance, especially in pathological cases, we can cache /Resources-entries when it's absolutely clear that they do not contain *any* blend modes at all[1]. This way, subsequent `PartialEvaluator.hasBlendModes` calls can be made significantly more efficient.

This patch was tested using the PDF file from issue 6961, i.e. https://github.com/mozilla/pdf.js/files/121712/test.pdf:
```
[
    {  "id": "issue6961",
       "file": "../web/pdfs/issue6961.pdf",
       "md5": "a80e4357a8fda758d96c2c76f2980b03",
       "rounds": 100,
       "type": "eq"
    }
]
```

which gave the following results when comparing this patch against the `master` branch:
```
-- Grouped By browser, page, stat --
browser | page | stat         | Count | Baseline(ms) | Current(ms) |  +/- |     %  | Result(P<.05)
------- | ---- | ------------ | ----- | ------------ | ----------- | ---- | ------ | -------------
firefox | 0    | Overall      |   100 |         1034 |         555 | -480 | -46.39 |        faster
firefox | 0    | Page Request |   100 |          489 |           7 | -482 | -98.67 |        faster
firefox | 0    | Rendering    |   100 |          545 |         548 |    2 |   0.45 |
firefox | 1    | Overall      |   100 |          912 |         428 | -484 | -53.06 |        faster
firefox | 1    | Page Request |   100 |          487 |           1 | -486 | -99.77 |        faster
firefox | 1    | Rendering    |   100 |          425 |         427 |    2 |   0.51 |
```

---
[1] In the case where blend modes *are* found, it becomes a lot more difficult to know if it's generally safe to skip /Resources-entries. Hence we don't cache anything in that case, however note that most document/pages do not utilize blend modes anyway.
This commit is contained in:
Jonas Jenwald 2020-11-05 13:35:33 +01:00
parent 8b652d685b
commit 082cd8fc6c
4 changed files with 41 additions and 5 deletions
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8
src/core/document.js
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@ -76,6 +76,7 @@ class Page {
fontCache,
builtInCMapCache,
globalImageCache,
nonBlendModesSet,
}) {
this.pdfManager = pdfManager;
this.pageIndex = pageIndex;
@ -85,6 +86,7 @@ class Page {
this.fontCache = fontCache;
this.builtInCMapCache = builtInCMapCache;
this.globalImageCache = globalImageCache;
this.nonBlendModesSet = nonBlendModesSet;
this.evaluatorOptions = pdfManager.evaluatorOptions;
this.resourcesPromise = null;
@ -312,7 +314,10 @@ class Page {
const opList = new OperatorList(intent, sink);
handler.send("StartRenderPage", {
transparency: partialEvaluator.hasBlendModes(this.resources),
transparency: partialEvaluator.hasBlendModes(
this.resources,
this.nonBlendModesSet
),
pageIndex: this.pageIndex,
intent,
});
@ -917,6 +922,7 @@ class PDFDocument {
fontCache: catalog.fontCache,
builtInCMapCache: catalog.builtInCMapCache,
globalImageCache: catalog.globalImageCache,
nonBlendModesSet: catalog.nonBlendModesSet,
});
}));
}