For e.g. `gulp mozcentral`, the *built* `pdf.worker.js` file decreases from `1 837 608` to `1 834 907` bytes with this patch-series.
The improvement comes first of all from less overall indentation in `PDFFunction`, and secondly from the removal of (now) unnecessary indirection in the code.
*This follows the exact same princial as PR 12083, but for the `PDFFunction` parsing instead.*
Given that the IR format is completely unused now, all that the current code does is add a bunch of unnecessary indirection/overhead to the handling of PDF-functions.
This is done automatically with `gulp lint --fix` and the following
manual changes:
```diff
diff --git a/src/core/function.js b/src/core/function.js
index 878001057..b7e3e6ccf 100644
--- a/src/core/function.js
+++ b/src/core/function.js
@@ -131,7 +131,7 @@ function toNumberArray(arr) {
return arr;
}
-var PDFFunction = (function PDFFunctionClosure() {
+const PDFFunction = (function PDFFunctionClosure() {
const CONSTRUCT_SAMPLED = 0;
const CONSTRUCT_INTERPOLATED = 2;
const CONSTRUCT_STICHED = 3;
@@ -484,7 +484,9 @@ var PDFFunction = (function PDFFunctionClosure() {
// clip to domain
const v = clip(src[srcOffset], domain[0], domain[1]);
// calculate which bound the value is in
- for (var i = 0, ii = bounds.length; i < ii; ++i) {
+ const length = bounds.length;
+ let i;
+ for (i = 0; i < length; ++i) {
if (v < bounds[i]) {
break;
}
@@ -673,23 +675,21 @@ const PostScriptStack = (function PostScriptStackClosure() {
roll(n, p) {
const stack = this.stack;
const l = stack.length - n;
- let r = stack.length - 1,
- c = l + (p - Math.floor(p / n) * n),
- i,
- j,
- t;
- for (i = l, j = r; i < j; i++, j--) {
- t = stack[i];
+ const r = stack.length - 1;
+ const c = l + (p - Math.floor(p / n) * n);
+
+ for (let i = l, j = r; i < j; i++, j--) {
+ const t = stack[i];
stack[i] = stack[j];
stack[j] = t;
}
- for (i = l, j = c - 1; i < j; i++, j--) {
- t = stack[i];
+ for (let i = l, j = c - 1; i < j; i++, j--) {
+ const t = stack[i];
stack[i] = stack[j];
stack[j] = t;
}
- for (i = c, j = r; i < j; i++, j--) {
- t = stack[i];
+ for (let i = c, j = r; i < j; i++, j--) {
+ const t = stack[i];
stack[i] = stack[j];
stack[j] = t;
}
@@ -939,7 +939,7 @@ class PostScriptEvaluator {
// We can compile most of such programs, and at the same moment, we can
// optimize some expressions using basic math properties. Keeping track of
// min/max values will allow us to avoid extra Math.min/Math.max calls.
-var PostScriptCompiler = (function PostScriptCompilerClosure() {
+const PostScriptCompiler = (function PostScriptCompilerClosure() {
class AstNode {
constructor(type) {
this.type = type;
```
Using `for...of` is a modern and generally much nicer pattern, since it gets rid of unnecessary callback-functions. (In a couple of spots, a "regular" `for` loop had to be used.)
All of this code predates the existence of native JS classes, however we can now clean this up a bit. This patch thus let us remove some variable "shadowing" from the code.
By changing this a `shadow`ed getter, we can simply access it directly and not worry about it being initialized. I have no idea why I didn't just implement it this way in the first place.
There's built-in ESLint rule, see `sort-imports`, to ensure that all `import`-statements are sorted alphabetically, since that often helps with readability.
Unfortunately there's no corresponding rule to sort `export`-statements alphabetically, however there's an ESLint plugin which does this; please see https://www.npmjs.com/package/eslint-plugin-sort-exports
The only downside here is that it's not automatically fixable, but the re-ordering is a one-time "cost" and the plugin will help maintain a *consistent* ordering of `export`-statements in the future.
*Note:* To reduce the possibility of introducing any errors here, the re-ordering was done by simply selecting the relevant lines and then using the built-in sort-functionality of my editor.
This simplifies/consolidates the ESLint configuration slightly in the `src/` folder, and prevents the addition of any new files where `var` is being used.[1]
Hence we no longer need to manually add `/* eslint no-var: error */` in files, which is easy to forget, and can instead disable the rule in the `src/core/` files where `var` is still in use.
---
[1] Obviously the `no-var` rule can, in the same way as every other rule, be disabled on a case-by-case basis where actually necessary.
Note that compared other structures, such as e.g. Images and ColorSpaces, `Function`s are not referred to by name, which however does bring the advantage of being able to share the cache for an *entire* page.
Furthermore, similar to ColorSpaces, the parsing of individual `Function`s are generally fast enough to not really warrant trying to cache them in any "smarter" way than by reference. (Hence trying to do caching similar to e.g. Fonts would most likely be a losing proposition, given the amount of data lookup/parsing that'd be required.)
Originally I tried implementing this similar to e.g. the recently added ColorSpace caching (and in a couple of different ways), however it unfortunately turned out to be quite ugly/unwieldy given the sheer number of functions/methods where you'd thus need to pass in a `LocalFunctionCache` instance. (Also, the affected functions/methods didn't exactly have short signatures as-is.)
After going back and forth on this for a while it seemed to me that the simplest, or least "invasive" if you will, solution would be if each `PartialEvaluator` instance had its *own* `PDFFunctionFactory` instance (since the latter is already passed to all of the required code). This way each `PDFFunctionFactory` instances could have a local `Function` cache, without it being necessary to provide a `LocalFunctionCache` instance manually at every `PDFFunctionFactory.{create, createFromArray}` call-site.
Obviously, with this patch, there's now (potentially) more `PDFFunctionFactory` instances than before when the entire document shared just one. However, each such instance is really quite small and it's also tied to a `PartialEvaluator` instance and those are *not* kept alive and/or cached. To reduce the impact of these changes, I've tried to make as many of these structures as possible *lazily initialized*, specifically:
- The `PDFFunctionFactory`, on `PartialEvaluator` instances, since not all kinds of general parsing actually requires it. For example: `getTextContent` calls won't cause any `Function` to be parsed, and even some `getOperatorList` calls won't trigger `Function` parsing (if a page contains e.g. no Patterns or "complex" ColorSpaces).
- The `LocalFunctionCache`, on `PDFFunctionFactory` instances, since only certain parsing requires it. Generally speaking, only e.g. Patterns, "complex" ColorSpaces, and/or (some) SoftMasks will trigger any `Function` parsing.
To put these changes into perspective, when loading/rendering all (14) pages of the default `tracemonkey.pdf` file there's now a total of 6 `PDFFunctionFactory` and 1 `LocalFunctionCache` instances created thanks to the lazy initialization.
(If you instead would keep the document-"global" `PDFFunctionFactory` instance and pass around `LocalFunctionCache` instances everywhere, the numbers for the `tracemonkey.pdf` file would be instead be something like 1 `PDFFunctionFactory` and 6 `LocalFunctionCache` instances.)
All-in-all, I thus don't think that the `PDFFunctionFactory` changes should be generally problematic.
With these changes, we can also modify (some) call-sites to pass in a `Reference` rather than the actual `Function` data. This is nice since `Function`s can also be `Streams`, which are not cached on the `XRef` instance (given their potential size), and this way we can avoid unnecessary lookups and thus save some additional time/resources.
Obviously I had intended to include (standard) benchmark results with these changes, but for reasons I don't really understand the test run-time (even with `master`) of the document in issue 2541 is quite a bit slower than in the development viewer.
However, logging the time it takes for the relevant `PDFFunctionFactory`/`PDFFunction ` parsing shows that it takes *approximately* `0.5 ms` for the `Function` in question. Looking up a cached `Function`, on the other hand, is *one order of magnitude faster* which does add up when the same `Function` is invoked close to 2000 times.
Please note that these changes were done automatically, using `gulp lint --fix`.
Given that the major version number was increased, there's a fair number of (primarily whitespace) changes; please see https://prettier.io/blog/2020/03/21/2.0.0.html
In order to reduce the size of these changes somewhat, this patch maintains the old "arrowParens" style for now (once mozilla-central updates Prettier we can simply choose the same formatting, assuming it will differ here).
Given the way that "classes" were previously implemented in PDF.js, using regular functions and closures, there's a fair number of false positives when the `no-shadow` ESLint rule was enabled.
Note that while *some* of these `eslint-disable` statements can be removed if/when the relevant code is converted to proper `class`es, we'll probably never be able to get rid of all of them given our naming/coding conventions (however I don't really see this being a problem).
*This is part of a series of patches that will try to split PR 11566 into smaller chunks, to make reviewing more feasible.*
Once all the code has been fixed, we'll be able to eventually enable the ESLint no-shadow rule; see https://eslint.org/docs/rules/no-shadow
Rather than duplicating the lookup and caching in multiple files, it seems easier to simply move all of this functionality into `src/shared/util.js` instead.
This will also help avoid a bunch of ESLint errors once the `no-shadow` rule is eventually enabled.
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).
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`.
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.)
*Follow-up to PR 8909.*
This requires us to pass around `pdfFunctionFactory` to quite a lot of existing code, however I don't see another way of handling this while still guaranteeing that we can access `PDFFunction` as freely as in the old code.
Please note that the patch passes all tests locally (unit, font, reference), and I *very* much hope that we have sufficient test-coverage for the code in question to catch any typos/mistakes in the re-factoring.
Currently `PDFFunction` is implemented (basically) like a class with only `static` methods. Since it's used directly in a number of different `src/core/` files, attempting to pass in `isEvalSupported` would result in code that's *very* messy, not to mention difficult to maintain (since *every* single `PDFFunction` method call would need to include a `isEvalSupported` argument).
Rather than having to wait for a possible re-factoring of `PDFFunction` that would avoid the above problems by design, it probably makes sense to at least set `isEvalSupported` globally for `PDFFunction`.
Please note that there's one caveat with this solution: If `PDFJS.getDocument` is used to open multiple files simultaneously, with *different* `PDFJS.isEvalSupported` values set before each call, then the last one will always win.
However, that seems like enough of an edge-case that we shouldn't have to worry about it. Besides, since we'll also test that `eval` is actually supported, it should be fine.
Fixes 5573.
Please note that the `glyphlist.js` and `unicode.js` files are converted to CommonJS modules instead, since Babel cannot handle files that large and they are thus excluded from transpilation.
Please see http://eslint.org/docs/rules/object-shorthand.
For the most part, these changes are of the search-and-replace kind, and the previously enabled `no-undef` rule should complement the tests in helping ensure that no stupid errors crept into to the patch.
Please see http://eslint.org/docs/rules/spaced-comment.
Note that the exceptions added for `line` comments are intended to still allow use of the old preprocessor without linting errors.
Also, I took the opportunity to improve the grammar slightly (w.r.t. capitalization and punctuation) for comments touched in the patch.
*Please note that most of the necessary code adjustments were made in PR 7890.*
ESLint has a number of advantageous properties, compared to JSHint. Among those are:
- The ability to find subtle bugs, thanks to more rules (e.g. PR 7881).
- Much more customizable in general, and many rules allow fine-tuned behaviour rather than the just the on/off rules in JSHint.
- Many more rules that can help developers avoid bugs, and a lot of rules that can be used to enforce a consistent coding style. The latter should be particularily useful for new contributors (and reduce the amount of stylistic review comments necessary).
- The ability to easily specify exactly what rules to use/not to use, as opposed to JSHint which has a default set. *Note:* in future JSHint version some of the rules we depend on will be removed, according to warnings in http://jshint.com/docs/options/, so we wouldn't be able to update without losing lint coverage.
- More easily disable one, or more, rules temporarily. In JSHint this requires using a numeric code, which isn't very user friendly, whereas in ESLint the rule name is simply used instead.
By default there's no rules enabled in ESLint, but there are some default rule sets available. However, to prevent linting failures if we update ESLint in the future, it seemed easier to just explicitly specify what rules we want.
Obviously this makes the ESLint config file somewhat bigger than the old JSHint config file, but given how rarely that one has been updated over the years I don't think that matters too much.
I've tried, to the best of my ability, to ensure that we enable the same rules for ESLint that we had for JSHint. Furthermore, I've also enabled a number of rules that seemed to make sense, both to catch possible errors *and* various style guide violations.
Despite the ESLint README claiming that it's slower that JSHint, https://github.com/eslint/eslint#how-does-eslint-performance-compare-to-jshint, locally this patch actually reduces the runtime for `gulp` lint (by approximately 20-25%).
A couple of stylistic rules that would have been nice to enable, but where our code currently differs to much to make it feasible:
- `comma-dangle`, controls trailing commas in Objects and Arrays (among others).
- `object-curly-spacing`, controls spacing inside of Objects.
- `spaced-comment`, used to enforce spaces after `//` and `/*. (This is made difficult by the fact that there's still some usage of the old preprocessor left.)
Rules that I indend to look into possibly enabling in follow-ups, if it seems to make sense: `no-else-return`, `no-lonely-if`, `brace-style` with the `allowSingleLine` parameter removed.
Useful links:
- http://eslint.org/docs/user-guide/configuring
- http://eslint.org/docs/rules/
As evident from e.g. PRs 6485 and 7118, some bad PDF generators unfortunately create Arrays where *some* elements are indirect objects (i.e. `Ref`s). This seems to mostly affect Arrays that contain numbers, such as e.g. `Matrix/FontMatrix/BBox/FontBBox/Rect/Color/...`, and has manifested itself in PDF files that fail to render correctly (some elements are missing).
The problem in both the cases above, besides broken rendering, was that there were *no* errors/warnings that indicated what the problem was, making it difficult to pinpoint the issue.
Hence this patch, where I've audited all usages of `Dict_get` in `src/core/` files, and replaced it with `Dict_getArray` where appropriate to try and prevent unnecessary future bugs.
This allows the JS engine to do a better job of allocating the right
number of elements for the array, avoiding some resizings. For the PDF
in #2504, this avoids 100s of MiBs of allocations in Firefox.
