The vast majority of the time, unless a Pattern is active, the `strokeColor`-property contains a "simple" colour value represented by a String. Hence it seems somewhat ridiculous to do a `hasOwnProperty` check on a String, and it's should thus be possible to improve things a tiny bit here.
Unfortunately using a simple `instanceof` check would only work for `TilingPattern`s, but not for the `ShadingIRs` given how they are implemented; see `src/display/pattern_helper.js`. (While that file could probably do with some clean-up, given the age of some of its code, that probably shouldn't happen here.)
Finally, the `this.type = "Pattern"`-property of the various Shadings/TilingPatterns were removed, since I cannot see why it's necessary when we can simply check for a `getPattern` method instead. Note that part of this code even pre-dates the main/worker-thread split, which probably in part explains why it looks the way it does.
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.
Given the number of parameters, and the fact that many of them are booleans, the call-sites are no longer particularly easy to read and understand. Furthermore, this slightly improves the formatting of the JSDoc-comment, since it needed updating as part of these changes anyway.
Finally, this removes an unnecessary `numViews === 0` check from `getVisibleElements`, since that should be *very* rare and more importantly that the `binarySearchFirstItem` function already has a fast-path for that particular case.
* it's faster to generate the color code in using a table for components
* it's very likely a way faster to parse (when setting the color in the canvas)
*Please note:* I cannot be sure if this actually helps, since we've not enabled LGTM for the PDF.js repository[1], however I hope that it should stop LGTM reporting things that we're already using ESLint to enforce.
---
[1] In case the patch does nothing, we can simply revert it and move on :-)
This patch addresses a review comment, which pointed out that we should *also* handle the pageNumber-input, from PR 12493.
Given that a user *manually* changing pages using the pageNumber-input, on the toolbar, could be regarded as a pretty strong indication of user-intent w.r.t. navigation in the document, hence I suppose that updating the browser history in this case as well probably won't hurt.
All of these methods will, in one way or another, cause e.g. scrolling or zooming to occur and consequently they don't really make sense unless there's an active PDF document. Especially since all of these methods end up calling into a `BaseViewer`-instance, which already contains similar early returns in essentially all of it's methods and setters.
This fixes only those warnings, as reported by https://lgtm.com/projects/g/mozilla/pdf.js?mode=list, that make sense (as far as I'm concerned).
Hence this patch leaves the following things unaddressed:
- The "recommendation"-category, since it only complains about unused variables. However, note that all of those cases are purposely included and that there's thus ESLint-disable comments added to explictly allow them.
- The "warning"-category, which still contains two complaints. However, as far as I can tell, they are both false positives.
Given first of all the false positives of the LGTM static analyzer, and secondly that we'd need to add (essentially duplicated) disable-comments for the unused variable cases, it's not entirely clear to me if we actually want to work towards including LGTM in the PDF.js project (e.g. running alongside Travis) or if we should just close issue 11965.
Given that the `Map`-pattern apparently has undesirable performance characteristics, change this getter back to using an Object instead and check its size before returning it.
Rather than returning an *empty* Object[1] we should be returning `null` instead, since that's consistent with existing API-functionality.
To avoid having to *manually* track if the Object is empty, this patch also introduces a small helper function to check its size.
As can be seen in `src/core/fonts.js`, this method only accepts *one* parameter, hence it's somewhat difficult to understand what the Annotation-code is actually attempting to do here.
The only possible explanation that I can imagine, is that the intention was initially to call `Font.charToGlyph` *directly* instead. However, note that that'd would not actually have been correct, since that'd ignore one level of font-caching (see `this.charsCache`). Hence the unused arguments are removed, in `src/core/annotation.js`, and the `Font.charToGlyph` method is now marked as "private" as intended.
This patch removes unnecessary escape-sequence in (mostly) strings, as a first step, since the ones in regular expressions probably requires more careful testing (just in case).
The only exception is a regular expression in `src/core/annotation.js`, since we should have both unit- and reference-tests for this code *and* given [this information on MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions/Character_Classes#Types):
> Inside a character set, the dot loses its special meaning and matches a literal dot.
Please find additional details about the ESLint rule at https://eslint.org/docs/rules/no-useless-escape
Given that `Object.fromEntries` doesn't seem to *guarantee* that a `null` prototype is used, we thus hack around that by using `Object.assign` with `Object.create(null)`.
This provides a work-around to avoid having to conditionally try to initialize the `openAction`-object in multiple places.
Given that `Object.fromEntries` doesn't seem to *guarantee* that a `null` prototype is used, we thus hack around that by using `Object.assign` with `Object.create(null)`.
This probably ought to have been included in PR 12534, but better late than never I suppose, since it helps to more clearly demonstrate the bug in a way that a reference-test alone just cannot do.
When writing this unit-test I also noticed that it required a certain amount of "luck" to actually trigger the bug, prior to the patch, since it seems that the bug only reproduced for certain *unfortunate* sequences of TypedArray data. (The added unit-test contains one such, purposely simple, example.)
Given that we're now accessing certain API-functionality *directly* in this file, e.g. the AnnotationStorage and Optional Content configuration, ensuring that there's not a version mismatch definitely seem like a good idea to prevent any *subtle* future bugs.
The unit-test files themselves shouldn't be loaded until Jasmine has been setup/configured, however that doesn't matter for the "normal" PDF.js library files. Hence we can simply `import` them in the standard way.
