All objects in the PDF document follow this pattern:
```
0000000001 0 obj
<<
% Some content here...
>>
endobj
0000000002 0 obj
<<
% More content here...
endobj
```
In many cases in the code you don't actually care about the index itself, but rather just want to know if something exists in a String/Array or if a String starts in a particular way. With modern JavaScript functionality, it's thus possible to remove a number of existing `indexOf` cases.
The `toString` method always creates two string objects (for the 'R'
character and for the `num` concatenation) and in the worst case
creates three string objects (one more for the `gen` concatenation).
For the Tracemonkey paper alone, this resulted in 12000 string
objects when scrolling from the top to the bottom of the document.
Since this is a hot function, it's worth minimizing the number of string
objects, especially for large documents, to reduce peak memory usage.
This commit refactors the `toString` method to always create only one
string object.
For PDF documents with sufficiently broken XRef tables, it's usually quite obvious when you need to fallback to indexing the entire file. However, for certain kinds of corrupted PDF documents the XRef table will, for all intents and purposes, appear to be valid. It's not until you actually try to fetch various objects that things will start to break, which is the case in the referenced issues[1].
Since there's generally a real effort being in made PDF.js to load even corrupt PDF documents, this patch contains a suggested approach to attempt to do a bit more validation of the XRef table during the initial document loading phase.
Here the choice is made to attempt to load the *first* page, as a basic sanity check of the validity of the XRef table. Please note that attempting to load a more-or-less arbitrarily chosen object without any context of what it's supposed to be isn't a very useful, which is why this particular choice was made.
Obviously, just because the first page can be loaded successfully that doesn't guarantee that the *entire* XRef table is valid, however if even the first page fails to load you can be reasonably sure that the document is *not* valid[2].
Even though this patch won't cause any significant increase in the amount of parsing required during initial loading of the document[3], it will require loading of more data upfront which thus delays the initial `getDocument` call.
Whether or not this is a problem depends very much on what you actually measure, please consider the following examples:
```javascript
console.time('first');
getDocument(...).promise.then((pdfDocument) => {
console.timeEnd('first');
});
console.time('second');
getDocument(...).promise.then((pdfDocument) => {
pdfDocument.getPage(1).then((pdfPage) => { // Note: the API uses `pageNumber >= 1`, the Worker uses `pageIndex >= 0`.
console.timeEnd('second');
});
});
```
The first case is pretty much guaranteed to show a small regression, however the second case won't be affected at all since the Worker caches the result of `getPage` calls. Again, please remember that the second case is what matters for the standard PDF.js use-case which is why I'm hoping that this patch is deemed acceptable.
---
[1] In issue 7496, the problem is that the document is edited without the XRef table being correctly updated.
In issue 10326, the generator was sorting the XRef table according to the offsets rather than the objects.
[2] The idea of checking the first page in particular came from the "standard" use-case for the PDF.js library, i.e. the default viewer, where a failure to load the first page basically means that nothing will work; note how `{BaseViewer, PDFThumbnailViewer}.setDocument` depends completely on being able to fetch the *first* page.
[3] The only extra parsing is caused by, potentially, having to traverse *part* of the `Pages` tree to find the first page.
Note that the OpenAction dictionary may contain other information besides just a destination array, e.g. instructions for auto-printing[1].
Given first of all that an arbitrary `Dict` cannot be sent from the Worker (since cloning would fail), and second of all that the data obviously needs to be validated, this patch purposely only adds support for fetching a destination from the OpenAction entry[2].
---
[1] This information is, currently in PDF.js, being included through the `getJavaScript` API method.
[2] This significantly reduces the complexity of the implementation, which seems fine for now. If there's ever need for other kinds of OpenAction to be fetched, additional API methods could/should be implemented as necessary (could e.g. follow the `getOpenActionWhatever` naming scheme).
The custom entries, provided that they exist *and* that their types are safe to include, are exposed through a new `Custom` infoDict entry to clearly separate them from the standard ones.
Fixes 5970.
Fixes 10344.
Given that Signature (Widget) annotations are currently not supported, since they cannot be validated, simply ignoring the `fieldValue` seems OK for now considering that attempting to blindly include unparsed/unvalidated data isn't very useful.
Fixes 10347.
The intent of the code, based on existing comments, is to perform a binary search. However, because of what appears to be a typo in the code responsible for computing the current search index, this code is always checking *every* entry (albeit only at the "final" node) starting from the last one.
According to the specification, see https://www.adobe.com/content/dam/acom/en/devnet/acrobat/pdfs/PDF32000_2008.pdf#G6.2384179, the keys of NameTree/NumberTree should be ordered.
For corrupt PDF files, which violate this assumption, we thus need to fallback to an exhaustive search in order to e.g. find all destinations.
*Please note:* Given that this only implements a fallback for the "final" node of the Tree, there's obviously a risk that the patch isn't sufficient for dealing with all kinds of out-of-order corruption. However, this kind of problem should be rare in practice, and without a real-world test-case it's difficult to implement a completely general solution (and there's obviously a question if you'd even want to).
These interfaces are already used in different files, in both the `src/core/` and `src/display/` folders, and having them reside in their own file seems a lot clearer and is also similar to the existing viewer interfaces.
As part of moving the `interface` definitions, they're also converted to ES6 classes.
The `Font.loading` property is only ever used *once* in the code, whereas `Font.missingFile` is more widely used. Furthermore the name `loading` feels, at least to me, slight less clear than `missingFile`. Finally, note that these two properties are the inverse of each other.
Currently there's only a single spot in the code-base where `JpegImage.getData` is called, however it nonetheless seem like a good idea to ensure during tests that the `isSourcePDF` parameter is correctly set. (Especially considering that the PDF use-cases will break without it.)
Additionally, in `JpegImage._getLinearizedBlockData`, the code can be made a tiny bit more efficient by checking the value of `isSourcePDF` *first* to avoid useless checks (for the default PDF use-cases).
There have been lots of problems with trying to map glyphs to their unicode
values. It's more reliable to just use the private use areas so the browser's
font renderer doesn't mess with the glyphs.
Using the private use area for all glyphs did highlight other issues that this
patch also had to fix:
* small private use area - Previously, only the BMP private use area was used
which can't map many glyphs. Now, the (much bigger) PUP 16 area can also be
used.
* glyph zero not shown - Browsers will not use the glyph from a font if it is
glyph id = 0. This issue was less prevalent when we mapped to unicode values
since the fallback font would be used. However, when using the private use
area, the glyph would not be drawn at all. This is illustrated in one of the
current test cases (issue #8234) where there's an "ä" glyph at position
zero. The PDF looked like it rendered correctly, but it was actually not
using the glyph from the font. To properly show the first glyph it is always
duplicated and appended to the glyphs and the maps are adjusted.
* supplementary characters - The private use area PUP 16 is 4 bytes, so
String.fromCodePoint must be used where we previously used
String.fromCharCode. This is actually an issue that should have been fixed
regardless of this patch.
* charset - Freetype fails to load fonts when the charset size doesn't match
number of glyphs in the font. We now write out a fake charset with the
correct length. This also brought up the issue that glyphs with seac/endchar
should only ever write a standard charset, but we now write a custom one.
To get around this the seac analysis is permanently enabled so those glyphs
are instead always drawn as two glyphs.
The purpose of this patch is to provide a better default behaviour when `JpegImage` is used to parse standalone JPEG images with CMYK colour spaces.
Since the issue that the patch concerns is somewhat of a special-case, the implementation utilizes the already existing decode support in an attempt to minimize the impact w.r.t. code size.
*Please note:* It's always possible for the user of `JpegImage` to control image inversion, and thus override the new behaviour, by simply passing a custom `decodeTransform` array upon initialization.
Apparently there's some PDF generators, in this case the culprit is "Nooog Pdf Library / Nooog PStoPDF v1.5", that manage to mess up PDF creation enough that endstream[1] commands actually become truncated.
*Please note:* The solution implemented here isn't perfect, since it won't be able to cope with PDF files that contains a *mixture* of correct and truncated endstream commands.
However, considering that this particular mode of corruption *fortunately* doesn't seem very common[2], a slightly less complex solution ought to suffice for now.
Fixes 10004.
---
[1] Scanning through the PDF data to find endstream commands becomes necessary, in order to determine the stream length in cases where the `Length` entry of the (stream) dictionary is missing/incorrect.
[2] I cannot recall having seen any (previous) issues/bugs with "Missing endstream" errors.
Reduces the amount of boilerplate code when defining the the sub-classes.
Please note that a couple of the closures were kept, since it's not (yet) possible to include helper functions inside of `class`es.
This property is not only completely unused now, it never actually appears to have been used. Even though the memory savings, from not initializing these extra typed arrays, won't be significant in the grand scheme of things it still seems completely unnecessary to keep allocating this data.
As far as I can tell, the main reason for the existence of `defaultColor` seem to be for documentation purposes. Hence the code is changed into comments instead, to keep the information around (but without the unnecessary allocations).
For proof-of-concept, this patch converts a couple of `Promise` returning methods to use `async` instead.
Please note that the `generic` build, based on this patch, has been successfully testing in IE11 (i.e. the viewer loads and nothing is obviously broken).
Being able to use modern JavaScript features like `async`/`await` is a huge plus, but there's one (obvious) side-effect: The size of the built files will increase slightly (unless `SKIP_BABEL == true`). That's unavoidable, but seems like a small price to pay in the grand scheme of things.
Finally, note that the `chromium` build target was changed to no longer skip Babel translation, since the Chrome extension still supports version `49` of the browser (where native `async` support isn't available).
Not only is this method completely unused *now*, looking through the history of the code it never appears to have been used for anything either.
Years ago `mainXRefEntriesOffset` was included when creating `XRef` instances, however it wasn't actually used for anything (the parameter was never checked, nor assigned to a property on `XRef`).
If this method ever becomes useful (again) it's easy enough to restore it thanks to version control, but including dead code in the builds just seems wasteful.
Please note that while this *improves* issue 9984 slightly (and likely others too), it's not a complete solution.
The remaining issues are related to the, more general, problems with the existing heuristics related to attempting to combine separate text items.
One of the `QueueOptimizer` cases wasn't updated to use `Uint8ClampedArray`s, which leads to inconsistent image data on the API side (but no actual rendering bugs, as far as I can tell).
To prevent future errors, a non-production/test-only `assert` was added to ensure that the relevant image data only uses `Uint8ClampedArray`s.
This commit is the first step towards implementing parsing for the
appearance streams of annotations.
Co-authored-by: Jonas Jenwald <jonas.jenwald@gmail.com>
Co-authored-by: Tim van der Meij <timvandermeij@gmail.com>
The current font type/subtype detection code is quite inconsistent/unwieldy. In some cases it will simply assume that the font dictionary is correct, in others it will somewhat "arbitrarily" check the actual font file (more of these cases have been added over the years to fix specific bugs).
As is evident from e.g. issue 9949, the font type/subtype detection code is continuing to cause issues. In an attempt to get rid of these hacks once and for all, this patch instead re-factors the type/subtype detection to *always* parse the font file.
Please note that, as far as I can tell, we still appear to need to rely on the composite font detection based on the font dictionary. However, even if the composite/non-composite detection would get it wrong, that shouldn't really matter too much given that there's basically only two different code-paths (for "TrueType-like" vs "Type1-like" fonts).
The font in the PDF is marked as a CIDFontType0, but the font file is
actually a true type font. To fully address this issue we should really
peek into the font file and try to determine what it is. However, this
is the first case of this issue, so I think this solution is acceptable for
now.
Fixes a stupid oversight on my part, since /Filter may (obviously) contain an Array, which resulted in unnecessary console warning spam in perfectly valid PDF files.
Note that it still makes sense to check that /Filter is actually a Name, before attempting to access its `name` property, but the warning should definitely be removed.
According to the PDF specification, see https://www.adobe.com/content/dam/acom/en/devnet/acrobat/pdfs/PDF32000_2008.pdf#page=45
> When using the JPXDecode filter with image XObjects, the following changes to and constraints on some entries in the image dictionary shall apply (see 8.9.5, "Image Dictionaries" for details on these entries):
>
> - Width and Height shall match the corresponding width and height values in the JPEG2000 data.
>
> - . . .
Hence it seems reasonable to use the Width/Height of the image data *itself*, rather than the image dictionary when there's a mismatch. Given that JPEG 2000 images are already being parsed, in order to obtain basic parameters, the actual Width/Height is readily available in the `PDFImage` constructor.
Given that the code is currently assuming that the /Filter entry is a `Name`, it cannot hurt to actually ensure that's the case.
Also fixes an error message, for JPEG 2000 images with unsupported ColorSpaces, since `this.numComps` hasn't been initialized when it's accessed during the `throw new Error()` invocation.
[api-minor] Add an `IsLinearized` property to the `PDFDocument.documentInfo` getter, to allow accessing the linearization status through the API (via `PDFDocumentProxy.getMetadata`)
Since PDF.js already supports range requests and streaming, not to mention chunked rendering, attempting to use the `Linearization` dictionary in `PDFDocument.getPage` probably isn't going to improve performance in any noticeable way.
Nonetheless, when `Linearization` data is available, it will allow looking up the first Page *directly* without having to descend into the `Pages` tree to find the correct object.
With the `builtInCMapCache` being a simple Object, it unfortunately means that the `Catalog.cleanup` method isn't resetting it as intended.
By just replacing the `builtInCMapCache` with an empty Object, existing references to it will not actually be updated. The result is that e.g. `Page` instances still keeps references to, what should have been removed, CMap data.
To fix these problems, the `builtInCMapCache` is converted into a `Map` instead (since it can be easily reset).
There was a (somewhat) recent question on IRC about accessing the linearization status of a PDF document, and this patch contains a simple way to expose that through already existing API methods.
Please note that during setup/parsing in `PDFDocument` the linearization data is already being fetched and parsed, provided of course that it exists. Hence this patch will *not* cause any additional data to be loaded.
With this file now being a proper (ES6) module, it's no longer (technically) necessary for this structure to be lazily initialized. Considering its size, and simplicity, I therefore cannot see the harm in letting `DocumentInfoValidators` just be simple Object instead.
While I'm not aware of any bugs caused by the current code, it cannot hurt to add an `isDict` check in `PDFDocument.documentInfo` (since the current code assumes that `infoDict` being defined implies it also being a Dictionary).
Finally, the patch also converts a couple of `var` to `let`/`const`.
Note first of all that `PDFDocument` will be initialized with either a `Stream` or a `ChunkedStream`, and that both of these have `length` getters. Secondly, the `PDFDocument` constructor will assert that the `stream` has a non-zero (and positive) length. Hence there's no point in checking `stream.length` in the `linearization` getter.
For most other `DecodeStream` based streams, we'll attempt to estimate the minimum `buffer` length based on the raw stream data. The purpose of this is to avoid having to unnecessarily re-size the `buffer`, thus reducing the number of *intermediate* allocations necessary when decoding the stream data.
However, currently no such optimization is attempted for `StreamsSequenceStream`, and given that they can often be quite large that seems unfortunate. To improve this, at least somewhat, this patch utilizes the raw sizes of the `StreamsSequenceStream` sub-streams to estimate the minimum required `buffer` length.
Most likely this patch won't have a huge effect on memory consumption, however for pathological cases it should help reduce peak memory usage slightly.
One example is the PDF file in issue 2813, where currently the `StreamsSequenceStream` instances would grow their `buffer`s as `2 MiB -> 4 MiB -> 8 MiB -> 16 MiB -> 32 MiB`. With this patch, the same stream `buffers`s grow as `8 MiB -> 16 MiB -> 32 MiB`, thus avoiding a total of `12 MiB` of *intermediate* allocations (since there's two `StreamsSequenceStream` used, for rendering/text-extraction).
Compared to all the other (static) methods in `Util`, the `toRoman` one looks slightly out of place. Even more so considering that `Util` is being exposed through `pdfjsLib`, where access to a Roman numerals conversion method doesn't make much sense.
*I was feeling bored; so this is a very quick, and somewhat naive, attempt at fixing the bug.*
The breaking error, i.e. `Error during font loading: invalid array length`, was thrown when attempting to re-size the `stack` to a *negative* length when parsing the CALL functions.
Fixes https://bugzilla.mozilla.org/show_bug.cgi?id=1473809.
PR 6141 changed `CompiledFont.compileGlyph` to, in the general case, return an Array. However, that PR apparenly forgot to update the no-glyph, empty-glyph, and endchar-glyph code-path and a String was still being (incorrectly) returned.
Given the way that `FontFaceObject.getPathGenerator` (on the API side) is implemented, this shouldn't have caused any bugs despite the Worker possible returning unexpected data.
Incomplete path operators, in particular, can result in fairly chaotic rendering artifacts, as can be observed on page four of the referenced PDF file.
The initial (naive) solution that was attempted, was to simply throw a `FormatError` as soon as any invalid (i.e. too short) operator was found and rely on the existing `ignoreErrors` code-paths. However, doing so would have caused regressions in some files; see the existing `issue2391-1` test-case, which was promoted to an `eq` test to help prevent future bugs.
Hence this patch, which adds special handling for invalid path operators since those may cause quite bad rendering artifacts.
You could, in all fairness, argue that the patch is a handwavy solution and I wouldn't object. However, given that this only concerns *corrupt* PDF files, the way that PDF viewers (PDF.js included) try to gracefully deal with those could probably be described as a best-effort solution anyway.
This patch also adjusts the existing `warn`/`info` messages to print the command name according to the PDF specification, rather than an internal PDF.js enumeration value. The former should be much more useful for debugging purposes.
Fixes https://bugzilla.mozilla.org/show_bug.cgi?id=1443140.
This patch avoids choosing a (possible) 'trailer' dictionary that `XRef.parse` and/or the `Catalog` constructor/methods will reject anyway.
Since `XRef.indexObjects` is already parsing the entire PDF file, the extra dictionary look-ups added here shouldn't matter much. Besides, this is a fallback code-path that only applies to corrupt PDF files anyway.
Note that the `Catalog` constructor, and some of its methods, are already enforcing that the 'Root' dictionary is valid/well-formed. However, by doing additional validation already in `XRef.parse` there's a slightly larger chance that corrupt PDF files could be successfully parsed/rendered.
With the current code line-breaks are accepted not just after an operator, but after a decimal point as well. When looking at this again, the latter case seems prone to cause false positives and might also interfere with subsequent patches.
Hence this is code is adjusted to actually do what the original commit message says, and nothing more.
The purpose of this patch is to hopefully provide *slightly* better user ergonomics, if/when the PDF.js image decoders are used standalone.
This implementation is (basically) reverting the changes in PR 9386, in conjunction with code from the `parse` method found at https://github.com/notmasteryet/jpgjs/blob/master/src/pdfjs.js
Since `ColorSpace` now depends on the native clamping of `Uint8ClampedArray`, this patch adds non-production/test-only `assert`s to enforce that the expected TypedArray is used for the output.
These `assert`s are purposely *not* included in PRODUCTION builds since that would break rendering completely, as opposed to "only" displaying some weird colours, when a `Uint8Array` was used. Furthermore, these are mostly added to help catch explicit developer errors when working with the `ColorSpace` and `PDFImage` code.
Since the tests (currently) run with the `pdf.worker.js` file built, i.e. with `PRODUCTION = true` set, there's no simple way to add e.g. `assert` calls for both non-production *and* test-only builds without also affecting PRODUCTION builds.
The built-in image decoders are already using `Uint8ClampedArray` when returning data, and this patch simply extends that to the rest of the image/colorspace code.
As far as I can tell, the only reason for using manual clamping/rounding in the first place was because TypedArrays used to be polyfilled (using regular arrays). And trying to polyfill the native clamping/rounding would probably have been had too much overhead, but given that TypedArray support is required in PDF.js version `2.0` that's no longer a concern.
*Please note:* Because of different rounding behaviour, basically `Math.round` in `Uint8ClampedArray` respectively `Math.floor` in the old code, there will be very slight movement in quite a few existing test-cases. However, the changes should be imperceivable to the naked eye, given that the absolute difference is *at most* `1` for each RGB component when comparing `master` and this patch (see also the updated expectation values in the unit-tests).
The built-in image decoders are already returning data as `Uint8ClampedArray`, and subsequently the JPEG/JBIG2/JPX streams are as well. However, for general streams we obviously don't want to force the use of `Uint8ClampedArray` unless an "Image" is actually being decoded.
Hence this patch, which adds a parameter that allows the caller of the `getBytes`/`peekBytes` methods to force a `Uint8ClampedArray` (rather than a `Uint8Array`) to be returned.
Since the old comment mentions a now unsupported browser, let's update it such that someone won't accidentally conclude that the code in question can be removed.
Since `PDFPageProxy` already provide getters for all the data returned by `GetPage` (in the Worker), there isn't any compelling reason for accessing the `pageInfo` directly on `PDFPageProxy`.
The patch also changes the `GetPage` handler, in `src/core/worker.js`, to use modern JavaScript features.
After PR 8617 the `PDFManagerReady` message handler function, in `src/display/api.js`, is now a no-op. Hence it seems completely unnecessary to keep sending this message from `src/core/worker.js`.
With native typed array support now being mandatory in PDF.js, since version 2.0, this probably isn't a huge problem even though the current code seems wrong (it was changed in PR 6571).
Note how in the `!(data instanceof Uint8Array)` case we're currently attempting to send `handler.send('test', 'main', false);` to the main-thread, which doesn't really make any sense since the signature of the method reads `send(actionName, data, transfers) {`.
Hence the data that's *actually* being sent here is `'main'`, with `false` as the transferList, which just seems weird. On the main-thread, this means that we're in this case checking `data && data.supportTypedArray`, where `data` contains the string `'main'` rather than being falsy. Since a string doesn't have a `supportTypedArray` property, that check still fails as expected but it doesn't seem great nonetheless.
The `MessageHandler` itself, and its assorted helper functions, are currently the single largest[1] piece of code in the `src/shared/util.js` file. By moving this code into its own file, `src/shared/util.js` thus becomes smaller and more manageable.
Please note that while the current code works, both in the viewer and the unit-tests, it can leave the `WorkerTransport._passwordCapability` Promise in a pending state.
In the `PasswordRequest` handler, in src/display/api.js, we're returning the Promise from a `capability` object (rather than just a "plain" Promise). While an error thrown anywhere within this handler was fortunately enough to propagate it to the Worker side, it won't cause the Promise (in `WorkerTransport._passwordCapability`) to actually be rejected.
Finally note that while we're now catching errors in the `PasswordRequest` handler, those errors are still propagated to the Worker side via the (now) rejected Promise and the existing `return this._passwordCapability.promise;` line.
This prevents warnings about uncaught Promises, with messages such as "Error: Worker was destroyed during onPassword callback", when running the unit-tests both in browsers *and* in Node.js/Travis.
This avoids the initialization of, potentially thousands of, unnecessary `Stream` objects, by getting the required number of bytes directly instead.
Given the special behaviour, when `length === 0`, of the `getBytes`/`skip` methods, it's also necessary to handle that particular case to prevent errors when encountering empty CharStrings.
The current PageLabel dictionary validation code won't catch some (unlikely) forms of corruption. For example: a `Type`/`S` entry being `null`/`0`/empty string, a `P`/`St` entry being `null`/`0`.
Please note: I'm not aware of any bugs caused by the old code, but I've had this patch sitting locally for some time and figured it couldn't hurt to submit it.
This function combines the logic of two separate methods into one.
The loop limit is also a good thing to have for the calls in
`src/core/annotation.js`.
Moreover, since this is important functionality, a set of unit tests and
documentation is added.
It's only used in two places in the class and those callsites can
directly get the information from the dictionary, which is more readable
and avoids an additional method call.
With PDF.js version `2.0` we'll only support browsers with built-in `TypedArray` functionality, hence there doesn't seem to be any good reason not to implement this now.
Fixes 4888.
The reason for the bug is that we're only computing a checksum of the image data itself, but completely ignore the inline dictionary. The latter is important, since in practice it's not uncommon for inline images to be identical but use e.g. different ColourSpaces.
There's obviously a couple of different ways that we could compute a hash/checksum of the dictionary.
Initially I tried using `MurmurHash3_64` to compute a hash of the keys/values in the dictionary. Unfortunately this approach turned out to be *way* too slow in practice, especially for PDF files with a huge number of inline images; in particular issue 2618 would regresses quite badly with this solution.
The solution that is instead implemented in this patch, is to compute a checksum of the dictionary contents. While this is a much simpler, not to mention a lot more efficient, solution there's one drawback associated with it:
If the contents of inline image dictionaries are ordered differently, they will not be considered equal with this approach which could thus lead to failures to cache repeated inline images. In practice this doesn't seem to be a problem in any of the PDF files I've tested, and generally I'd rather err on the side of *not* caching given that too aggressive caching can easily lead to rendering bugs.
One small, but somewhat annoying, complication is that by the time `Parser.makeInlineImage` is called, we no longer know the *exact* stream position where the inline image dictionary starts. Having access to that information is crucial here, and the easiest solution I could come up with is to track this in the current `Lexer` instance.[1]
With the patch, we're thus able to fix the referenced issues without incurring large regressions in problematic cases such as issue 2618.
Fixes 9398; also improves/fixes the `issue8823` reference test.
---
[1] Obviously I'd have preferred if this patch could be limited to `Parser.makeInlineImage`, without the need for this "hack", but I'm not sure what that'd look like here.
Fallback to the built-in JPEG decoder when browser decoding fails, and attempt to handle JPEG images with DNL (Define Number of Lines) markers (issue 8614)
Please refer to the specification, found at https://www.w3.org/Graphics/JPEG/itu-t81.pdf#page=49
Given how the JPEG decoder is currently implemented, we need to know the value of the scanLines parameter (among others) *before* parsing of the SOS (Start of Scan) data begins.
Hence the best solution I could come up with here, is to re-parse the image in the *hopefully* rare case of JPEG images that include a DNL (Define Number of Lines) marker.
Fixes 8614.
This works by making `PartialEvaluator.buildPaintImageXObject` wait for the success/failure of `loadJpegStream` on the API side *before* parsing continues.
Please note that in practice, it should be quite rare for the browser to fail loading/decoding of a JPEG image. In the general case, it should thus not be completely surprising if even `src/core/jpg.js` will fail to decode the image.
This method currently requires a fair number of parameters, which creates quite unwieldy call-sites. When invoking `buildPaintImageXObject`, you have to remember not only which arguments to supply, but also the correct order, to prevent run-time errors.
