Note that `Dict.set` will only be called with values returned through `Parser.getObj`, and thus indirectly via `Lexer.getObj`. Since neither of those methods will ever return `undefined`, we can simply assert that that's the case when inserting data into the `Dict` and thus get rid of `in` checks when doing the data lookups.
In this case, since `Dict.set` is fairly hot, the patch utilizes an *inline check* and when necessary a direct call to `unreachable` to not affect performance of `gulp server/test` too much (rather than always just calling `assert`).
For very large and complex PDF files this will help performance *slightly*, since `Dict.{get, getAsync, has}` is called *a lot* during parsing in the worker.
This patch was tested using the PDF file from issue 2618, i.e. http://bugzilla-attachments.gnome.org/attachment.cgi?id=226471, with the following manifest file:
```
[
{ "id": "issue2618",
"file": "../web/pdfs/issue2618.pdf",
"md5": "",
"rounds": 250,
"type": "eq"
}
]
```
which gave the following results when comparing this patch against the `master` branch:
```
-- Grouped By browser, stat --
browser | stat | Count | Baseline(ms) | Current(ms) | +/- | % | Result(P<.05)
------- | ------------ | ----- | ------------ | ----------- | --- | ----- | -------------
Firefox | Overall | 250 | 2838 | 2820 | -18 | -0.65 | faster
Firefox | Page Request | 250 | 1 | 2 | 0 | 11.92 | slower
Firefox | Rendering | 250 | 2837 | 2818 | -19 | -0.65 | faster
```
Fixes#11477
The PDF draws many space characters but the embedded fonts don't have a glyph named `space`, so `.notdef` should be drawn instead. PDF.js assumed that Type1 fonts define `.notdef` as the first glyph (index 0). However, now the fonts have the glyph `A` at index 0 and `.notdef` is the last one, so `A` appears where spaces are expected.
Because the rest of the font machinery in `core/fonts.js` assumes `.notdef` is at index zero, it's easiest to modify `core/type1_parser.js` so that it "repairs" fonts and makes sure `.notdef` is at index 0.
The PDF document in question is *corrupt*, since it contains multiple instances of incorrect operators.
We obviously don't want to slow down parsing of *all* documents (since most are valid), just to accommodate a particular bad PDF generator, hence the reason for the inline check before calling the `ensureStateFont` method.
This patch extends the existing heuristics, which are really the best that we can do in general for these kinds of non-embedded *and* non-standard fonts.
Furthermore, this patch also tries to improve the copy-and-paste behaviour for non-embedded Wingdings fonts by also using the `ZapfDingbatsEncoding` in this case.
*Note:* I'm not sure that adding additional tests for Wingdings fonts matters that much, given how limited our "support" for them really is.
Given that all of these primitives implement caching, to avoid unnecessarily duplicating those objects *a lot* during parsing, it would thus be good to actually enforce usage of `Cmd.get()`/`Name.get()`/`Ref.get()` in the code-base.
Luckily it turns out that there's an ESLint rule, which is fairly easy to use, that can be used to disallow arbitrary JavaScript syntax.
Please find additional details about the ESLint rule at https://eslint.org/docs/rules/no-restricted-syntax
*This whole patch feels somewhat arbitrary, and I'd be slightly worried about possibly breaking something else.*
To limit the impact of these changes, we only re-parse JPEG images using a reduced `scanLines` value if and only if: An unexpected EOI (End of Image) marker was encountered during decoding of Scan data *and* the "actual" `scanLines` value is at least one order of magnitude smaller than expected.
In some cases PDF documents can contain JPEG images that the native browser decoder cannot handle, e.g. images with DNL (Define Number of Lines) markers or images where the SOF (Start of Frame) marker contains a wildly incorrect `scanLines` parameter.
Currently, for "simple" JPEG images, we're relying on native image decoding to *fail* before falling back to the implementation in `src/core/jpg.js`. In some cases, note e.g. issue 10880, the native image decoder doesn't outright fail and thus some images may not render.
In an attempt to improve the current situation, this patch adds additional validation of the JPEG image SOF data to force the use of `src/core/jpg.js` directly in cases where the native JPEG decoder cannot be trusted to do the right thing.
The only way to implement this is unfortunately to parse the *beginning* of the JPEG image data, looking for a SOF marker. To limit the impact of this extra parsing, the result is cached on the `JpegStream` instance and this code is only run for images which passed all of the pre-existing "can the JPEG image be natively rendered and/or decoded" checks.
---
*Slightly off-topic:* Working on this *really* makes me start questioning if native rendering/decoding of JPEG images is actually a good idea.
There's certain kinds of JPEG images not supported natively, and all of the validation which is now necessary isn't "free". At this point, in the `NativeImageDecoder`, we're having to check for certain properties in the image dictionary, parse the `ColorSpace`, and finally read the actual image data to find the SOF marker.
Furthermore, we cannot just send the image to the main-thread and be done in the "JpegStream" case, but we also need to wait for rendering to complete (or fail) before continuing with other parsing.
In the "JpegDecode" case we're even having to parse part of the image on the main-thread, which seems completely at odds with the principle of doing all heavy parsing in the Worker, and there's also a couple of potentially large (temporary) allocations/copies of TypedArray data involved as well.
Given that this is completely unused, and that a "normal" function call may be a *tiny* bit more efficient, there's no good reason as far as I can tell to keep it.
Over the years there's been a fair number of issues/PRs opened, where people have wanted to add `hasOwnProperty` checks in (hot) loops in the font parsing code. This has always been rejected, since we don't want to risk reducing performance in the Firefox PDF viewer simply because some users of the general PDF.js library are *incorrectly* extending the `Array.prototype` with enumerable properties.
With this patch the general PDF.js library will now fail immediately with a hopefully useful Error message, rather than having (some) fonts fail to render, when the `Array.prototype` is incorrectly extended.
Note that I did consider making this a warning, but ultimately decided against it since it's first of all possible to disable those (with the `verbosity` parameter). Secondly, even when printed, warnings can be easy to overlook and finally a warning may also *seem* OK to ignore (as opposed to an actual Error).
While it would be nice to change the `PDFFormatVersion` property, as returned through `PDFDocumentProxy.getMetadata`, to a number (rather than a string) that would unfortunately be a breaking API change.
However, it does seem like a good idea to at least *validate* the PDF header version on the worker-thread, rather than potentially returning an arbitrary string.
As can be seen in the code, the `xScaleBlockOffset` typed array doesn't depend on the actual image data but only on the width and x-scale. The width is obviously consistent for an image, and it turns out that in practice the `componentScaleX` is quite often identical between two (or more) adjacent image components.
All-in-all it's thus not necessary to *unconditionally* re-compute the `xScaleBlockOffset` when getting the JPEG image data.
While avoiding, in many cases, one or more loops can never be a bad thing these changes are unfortunately completely dominated by the rest of the JpegImage code and consequently doesn't really show up in benchmark results. *Hence I'd understand if this patch is ultimately deemed not necessary.*
*Note:* This is inspired by PR 5473, which made similar changes for another kind of JPEG data.
Since the implementation in `src/core/jpg.js` only supports 8-bit data, as opposed to similar code in `src/core/colorspace.js`, the computations can be further simplified since the `scale` is always constant.
By updating the coefficients, effectively inlining the `scale`, we'll thus avoid *four* multiplications for each loop iteration.
Unfortunately I wasn't able, based on a quick look through the test-files, to find a sufficiently *large* CMYK JPEG image in order for these changes to really show up in benchmark results. However, when testing the `cmykjpeg.pdf` manually there's a total of `120 000` fewer multiplication with this patch.
- Re-factor the "incorrect encoding" check, since this can be easily achieved using the general `findNextFileMarker` helper function (with a suitable `startPos` argument).
- Tweak a condition, to make it easier to see that the end of the data has been reached.
- Add a reference test for issue 1877, since it's what prompted the "incorrect encoding" check.
The other image decoders, i.e. the JBIG2 and JPEG 2000 ones, are using the common helper function `readUint16`. Most likely, the only reason that the JPEG decoder is doing it this way is because it originated *outside* of the PDF.js library.
Hence we can simply re-factor `src/core/jpg.js` to use the common `readUint16` helper function, which is especially nice given that the functionality was essentially *duplicated* in the code.
This covers cases that the `--fix` command couldn't deal with, and in a few cases (notably `src/core/jbig2.js`) the code was changed to use block-scoped variables instead.
Please find additional details about the ESLint rule at https://eslint.org/docs/rules/prefer-const
With the recent introduction of Prettier this sort of mass enabling of ESLint rules becomes a lot easier, since the code will be automatically reformatted as necessary to account for e.g. changed line lengths.
Note that this patch is generated automatically, by using the ESLint `--fix` argument, and will thus require some additional clean-up (which is done separately).
These two cases should have been whitelisted prior to re-formatting respectively had the comments fixed afterwards, however I unfortunately missed them because of the massive size of the diff.
Fixes#11403
The PDF uses the non-embedded Type1 font Helvetica. Character codes 194 and 160 (`Â` and `NBSP`) are encoded as `.notdef`. We shouldn't show those glyphs because it seems that Acrobat Reader doesn't draw glyphs that are named `.notdef` in fonts like this.
In addition to testing `glyphName === ".notdef"`, we must test also `glyphName === ""` because the name `""` is used in `core/encodings.js` for undefined glyphs in encodings like `WinAnsiEncoding`.
The solution above hides the `Â` characters but now the replacement character (space) appears to be too wide. I found out that PDF.js ignores font's `Widths` array if the font has no `FontDescriptor` entry. That happens in #11403, so the default widths of Helvetica were used as specified in `core/metrics.js` and `.nodef` got a width of 333. The correct width is 0 as specified by the `Widths` array in the PDF. Thus we must never ignore `Widths`.
This removes a couple of, thanks to preceeding code, unnecessary `typeof PDFJSDev` checks, and also fixes a couple of incorrectly implemented (my fault) checks intended for `TESTING` builds.
This way we'll benefit from the existing font caching, and can thus avoid re-creating a fallback font over and over again during parsing.
(Thece changes necessitated the previous patch, since otherwise breakage could occur e.g. with fake workers.)
This is beneficial in situations where the Worker is being re-used, for example with fake workers, since it ensures that things like font resources are actually released.
This rule is already enabled in mozilla-central, and helps avoid some confusing formatting, see https://searchfox.org/mozilla-central/rev/9e45d74b956be046e5021a746b0c8912f1c27318/tools/lint/eslint/eslint-plugin-mozilla/lib/configs/recommended.js#209-210
With the recent introduction of Prettier some of the existing nested ternary statements became even more difficult to read, since any possibly helpful indentation was removed.
This particular ESLint rule wasn't entirely straightforward to enable, and I do recognize that there's a certain amount of subjectivity in the changes being made. Generally, the changes in this patch fall into three categories:
- Cases where a value is only clamped to a certain range (the easiest ones to update).
- Cases where the values involved are "simple", such as Numbers and Strings, which are re-factored to initialize the variable with the *default* value and only update it when necessary by using `if`/`else if` statements.
- Cases with more complex and/or larger values, such as TypedArrays, which are re-factored to let the variable be (implicitly) undefined and where all values are then set through `if`/`else if`/`else` statements.
Please find additional details about the ESLint rule at https://eslint.org/docs/rules/no-nested-ternary
In order to eventually get rid of SystemJS and start using native `import`s instead, we'll need to provide "complete" file identifiers since otherwise there'll be MIME type errors when attempting to use `import`.
For reasons that I now cannot even begin to understand, the non-standard SegoeUISymbol font was placed in the `getStdFontMap`. That honestly makes no sense, hence this patch which does what I *should* have done from the start.
This patch makes the follow changes:
- Remove no longer necessary inline `// eslint-disable-...` comments.
- Fix `// eslint-disable-...` comments that Prettier moved down, thus causing new linting errors.
- Concatenate strings which now fit on just one line.
- Fix comments that are now too long.
- Finally, and most importantly, adjust comments that Prettier moved down, since the new positions often is confusing or outright wrong.
Note that Prettier, purposely, has only limited [configuration options](https://prettier.io/docs/en/options.html). The configuration file is based on [the one in `mozilla central`](https://searchfox.org/mozilla-central/source/.prettierrc) with just a few additions (to avoid future breakage if the defaults ever changes).
Prettier is being used for a couple of reasons:
- To be consistent with `mozilla-central`, where Prettier is already in use across the tree.
- To ensure a *consistent* coding style everywhere, which is automatically enforced during linting (since Prettier is used as an ESLint plugin). This thus ends "all" formatting disussions once and for all, removing the need for review comments on most stylistic matters.
Many ESLint options are now redundant, and I've tried my best to remove all the now unnecessary options (but I may have missed some).
Note also that since Prettier considers the `printWidth` option as a guide, rather than a hard rule, this patch resorts to a small hack in the ESLint config to ensure that *comments* won't become too long.
*Please note:* This patch is generated automatically, by appending the `--fix` argument to the ESLint call used in the `gulp lint` task. It will thus require some additional clean-up, which will be done in a *separate* commit.
(On a more personal note, I'll readily admit that some of the changes Prettier makes are *extremely* ugly. However, in the name of consistency we'll probably have to live with that.)
There's a fair number of (primarily) `Array`s/`TypedArray`s whose formatting we don't want disturb, since in many cases that would lead to the code becoming much more difficult to read and/or break existing inline comments.
*Please note:* It may be a good idea to look through these cases individually, and possibly re-write some of the them (especially the `String` ones) to reduce the need for all of these ignore commands.
During initial parsing of every PDF document we're currently creating a few `1 kB` strings, in order to find certain commands needed for initialization.
This seems inefficient, not to mention completely unnecessary, since we can just as well search through the raw bytes directly instead (similar to other parts of the code-base). One small complication here is the need to support backwards search, which does add some amount of "duplication" to this function.
The main benefits here are:
- No longer necessary to allocate *temporary* `1 kB` strings during initial parsing, thus saving some memory.
- In practice, for well-formed PDF documents, the number of iterations required to find the commands are usually very low. (For the `tracemonkey.pdf` file, there's a *total* of only 30 loop iterations.)
Given that the error in question is surfaced on the API-side, this patch makes the following changes:
- Updates the wording such that it'll hopefully be slightly easier for users to understand.
- Changes the plain `Error` to an `InvalidPDFException` instead, since that should work better with the existing Error handling.
- Adds a unit-test which loads an empty PDF document (and also improves a pre-existing `InvalidPDFException` message and its test-case).
