This patch uses nullish coalescing assignment in cases where it's immediately obvious from surrounding code that doing so is safe, and logical OR assignment elsewhere (mostly the changes in XFA code).
Using a `Map` rather than an `Object` is a nicer, since it has better support for both iteration and checking if a key exists.
We also change the initial values to be `null`, rather than empty strings, and reduce duplication when creating the `Map`.
*Please note:* Since this is worker-thread code, these changes are "invisible" at the API-level.
For simplicity we will abort /Form XObject parsing *immediately* when encountering a circular reference, rather than letting it continue up until some limit (as e.g. PDFium appears to do), which should be fine since there are never any guarantees if/how *corrupt* PDF documents will render.
In rare cases /Resources are also found in the /Contents stream-dict, in addition to in the /Page dict, hence we need to prefer those when available; see `issue18894.pdf`.
Previously we'd only do this for Type1/CFF fonts, see e.g. PR 6736, since the font-program may update the /FontMatrix.
However, it seems that we should do this unconditionally to account for fonts with non-default /FontMatrix-entries in the font-dictionary (which seem to be pretty rare).
In PDF version 2.0 the handling of Indexed color spaces was clarified as follows:
> The index value should be an integer in the range 0 to hival. If the value is a real number, it shall be rounded to the nearest integer (0.5 values shall be rounded up); if it is outside the range 0 to hival, it shall be adjusted to the nearest value within that range.
Please refer to https://github.com/pdf-association/pdf-differences/tree/main/IndexedColor
After the introduction of `OffscreenCanvas` support we now have *two separate* mask-methods in the `PDFImage` class, and the reason that they were not combined is likely that we need the "raw" bytes when parsing Type3-glyph image masks.
However, that case is easy to support simply by disabling `OffscreenCanvas` usage when parsing Type3-glyphs and that way we're able to reduce some code duplication.
Another slightly strange property of the `PDFImage.createMask` method is that it needs various image-dictionary parameters *manually* provided, which is probably because this is very old code.
That feels slightly unwieldy, and we instead change the method to pass in the image-stream directly and do the necessary data-lookup internally.
A side-effect of this re-factoring is that we now support using the custom `isSingleOpaquePixel` operator in Type3-glyphs, which shouldn't hurt even though it seems extremely unlikely for that to ever happen in Type3-glyphs.
This disallowd the following types of `export` declaration:
- `export class A {}`/`export function A() {}`
- `export default class A {}`/`export default function A() {}`
- `export let A`/`export const A`/`export var A`
While allowing
- `export { A }`
- `export default A`
These `getAll` methods are not used anywhere within the PDF.js code-base, outside of tests, and were mostly added (speculatively) for third-party users.
To still allow access to the same data we instead introduce iterators on these classes, which (slightly) shortens the code and allows us to remove the `objectFromMap` helper function.
A summary of the changes in this patch:
- Replace the `getAll` methods with iterators in the following classes: `AnnotationStorage`, `Metadata`, and `OptionalContentGroup`.
- Change, and also re-name, `AnnotationStorage.prototype.setAll` into a test-only method since it's not used elsewhere.
- Remove the `Metadata.prototype.has` method, since it's only used in tests and can be trivially replaced by calling `Metadata.prototype.get` and checking if the returned value is `null`.
We want to iterate through the data in the `computeMD5` function, and `Map`s have "nicer" support for that than generic objects.
(Somewhat recently `Map` performance was improved in Firefox, however this also isn't really performance sensitive code.)
It seems that the `@napi-rs/canvas` dependency has *basic* canvas-filter support, whereas the "old" `canvas` dependency didn't, hence we no longer need the Node.js-specific checks in the `src/display/canvas.js` file.
Note that I've successfully tested the [`pdf2png` example](https://github.com/mozilla/pdf.js/tree/master/examples/node/pdf2png) with this patch applied and things appear to work as before.
After PR 19731 the format of compiled Type3-glyphs is now simple enough that the compilation can be moved to the worker-thread, without introducing any significant additional complexity.
This allows us to, ever so slightly, simplify the implementation in `src/display/canvas.js` since the Type3 operatorLists will now directly include standard path-rendering operators (using the format introduced in PR 19689).
As part of these changes we also stop caching Type3 image masks since: we've not come across any cases where that actually helps, they're usually fairly small, and it simplifies the code.
Note that one "negative" change introduced in this patch is that we'll now compile Type3-glyphs *eagerly*, whereas previously we'd only do that lazily upon their first use.
However, this doesn't seem to impact performance in any noticeable way since the compilation is fast enough (way below 1 ms/glyph in my testing) and Type3-fonts are also limited to just 256 glyphs. Also, many (or most?) Type3-fonts don't even use image masks and are thus not affected by these changes.
In using the Firefox profiler (with JS allocations tracking) and wuppertal.pdf, I noticed
we were using a bit too much memory for a function which is supposed to just compute 2 numbers.
The memory used by itself isn't so important but having a too much objects lead to waste some time
to gc them.
So this patch aims to simplify it a bit.
Currently we explicitly specify the fn-`OPS` both when adding entries to the operatorList and to the image-caches, and by using a temporary variable we can reduce a bit of duplication (similar to the existing args-handling).
The color-parameter is already available through `IR` (i.e. the internal representation), and after the changes in PR 4824 (which landed in 2014) we no longer need any special handling for it.
In the included PDF document the Type3-font doesn't contain any glyph definition for "space", despite that character being referenced in the /Contents stream.
While missing Type3-glyphs obviously cannot be rendered, we still need to update the current canvas position such that any char/word-spacing is correctly applied.
The test-case was found at https://github.com/pdf-association/pdf-differences/tree/main/Type3WordSpacing
Similar to Webpack there's apparently other bundlers that will not leave `import`-calls alone unless magic comments are used.
Hence we extend the builder to also append `/* @vite-ignore */` comments to `import`-calls, in order to attempt to improve support for using the PDF.js builds together with Vite.
This patch also renames `__non_webpack_import__` to `__raw_import__` since the functionality is no longer bundler-specific.
***PLEASE NOTE:*** This patch is provided as-is, and it does *not* mean that the PDF.js project can/will provide official support for Vite.
Originally this function would "manually" invoke the rendering commands for Type3-glyphs, however that was changed some time ago:
- Initial `Path2D` support was added in PR 14858, but the old code kept for Node.js compatibility.
- Since PR 15951 we've been using a `Path2D` polyfill in Node.js environments.
Hence, after the previous commit, we can further simplify this function by *directly* returning/using the `Path2D` object when rendering Type3-glyphs; see also https://github.com/mozilla/pdf.js/pull/19731#discussion_r2018712695
While this won't improve performance significantly, when compared to the introduction of `Path2D`, it definately cannot hurt.
