Natively supported JPEG images are sent as-is, using a `blob:` or possibly a `data` URL, to the main-thread for loading/decoding.
However there's currently no attempt at releasing these resources, which are held alive by `blob:` URLs, which seems unfortunately given that images can be arbitrarily large.
As mentioned in https://developer.mozilla.org/en-US/docs/Web/API/URL/createObjectURL the lifetime of these URLs are tied to the document, hence they are not being removed when a page is cleaned-up/destroyed (e.g. when being removed from the `PDFPageViewBuffer` in the viewer).
This is easy to test with the help of `about:memory` (in Firefox), which clearly shows the number of `blob:` URLs becomming arbitrarily large *without* this patch. With this patch however the `blob:` URLs are immediately release upon clean-up as expected, and the memory consumption should thus be considerably reduced for long documents with (simple) JPEG images.
Note how `PDFDocumentProxy.destroy` is a nothing more than an alias for `PDFDocumentLoadingTask.destroy`. While removing the latter method would be a breaking API change, there's still room for at least some clean-up here.
The main changes in this patch are:
- Stop providing a `PDFDocumentLoadingTask` instance *separately* when creating a `PDFDocumentProxy`, since the loadingTask is already available through the `WorkerTransport` instance.
- Stop tracking the `PDFDocumentProxy` instance on the `WorkerTransport`, since that property is completely unused.
- Simplify the 'Multiple `getDocument` instances' unit-tests by only destroying *once*, rather than twice, for each document.
For Type3 fonts text-selection is often not that great, and there's a couple of heuristics used to try and improve things. This patch simple extends those heuristics a bit, and fixes a pre-existing "naive" array comparison, but this all feels a bit brittle to say the least.
The existing Type3 test-coverage isn't that great in general, and in particular Type3 `text` tests are few and far between, hence why this patch adds *two* different new `text` tests.
Notable changes:
- Remove the `return this;` from the `MurmurHash3_64.update` method, since it's completely unused and doesn't make a lot of sense.
- Remove the loop(s) from the `MurmurHash3_64.hexdigest` method, since creating a temporary array and then looping over it is wasteful given how simple this can be written with modern JavaScript.
The `DOMCanvasFactory` class is now fully covered. Moreover, missing
cases for the `getFilenameFromUrl` function have been included.
Finally, `var` usage has been removed.
The generated `default_preferences.json` file is necessary when initializing the Firefox preferences, which only supports certain types, hence this patch adds additional validation to help prevent run-time errors in Firefox.
Given that these changes add a code-path to `AppOptions.getAll` which could throw, the `OptionKind.PREFERENCE` branch is also modified to require *exact* matching to prevent (future) errors in the viewer.
Finally the conditionally defined `defaultOptions` will no longer (potentially) be considered during the `gulp default_preferences` task, to make it more difficult for them to be accidentally included.
Given that the function is (purposely) independent of the verbosity level and that its message is worded to only apply on the main-thread, there's no reason to duplicate this across the built `pdf.js`/`pdf.worker.js` files.
Currently for every single parsed/rendered page there's no less than *four* `Date.now()` calls being made on the worker-side. This seems totally unnecessary, since the result of these calls are, by default, not used for anything *unless* the verbosity level is set to `INFO`.
The default size of these canvases seem to be `300 x 150` (two orders of magnitude larger than the ones in PR 10597), which probably is sufficient enough to matter since there's one such canvas for each textLayer that's rendered in the viewer.
Also fixes the incorrect rejection reason, i.e. one using a string rather than an `Error`, in the `TextLayerRenderTask.cancel` method.
While this particular canvas may be small, there can still be an arbitrarily large number of them (one per page rendered), which can/will eventually add up memory wise. This can be easily avoided by using the `cachedCanvases` abstraction instead, which will ensure that the `isFontSubpixelAAEnabled` canvas is removed together with other temporary canvases in `CanvasGraphics.endDrawing`.
