The Puppeteer update should in particular be helpful for us because it
contains improved WebDriver BiDi compatibility, a newer Chrome version
(both might help for #17962) and an official deprecation of CDP for
Firefox. Note that the latter doesn't require changes on our end because
we already use WebDriver BiDi unconditionally for Firefox since commit
4db0174. The full release notes can be found at
https://github.com/puppeteer/puppeteer/releases/tag/puppeteer-core-v22.8.0.
When seleciting on a touch screen device, whenever the finger moves to a
blank area (so over `div.textLayer` directly rather than on a `<span>`),
the selection jumps to include all the text between the beginning of the
.textLayer and the selection side that is not being moved.
The existing selection flickering fix when using the mouse cannot be
trivially re-used on mobile, because when modifying a selection on
a touchscreen device Firefox will not emit any pointer event (and
Chrome will emit them inconsistently). Instead, we have to listen to the
'selectionchange' event.
The fix is different in Firefox and Chrome:
- on Firefox, we have to make sure that, when modifying the selection,
hovering on blank areas will hover on the .endOfContent element
rather than on the .textLayer element. This is done by adjusting the
z-indexes so that .endOfContent is above .textLayer.
- on Chrome, hovering on blank areas needs to trigger hovering on an
element that is either immediately after (or immediately before,
depending on which side of the selection the user is moving) the
currently selected text. This is done by moving the .endOfContent
element around between the correct `<span>`s in the text layer.
The new anti-flickering code is also used when selecting using a mouse:
the improvement in Firefox is only observable on multi-page selection,
while in Chrome it also affects selection within a single page.
After this commit, the `z-index`es inside .textLayer are as follows:
- .endOfContent has `z-index: 0`
- everything else has `z-index: 1`
- except for .markedContent, which have `z-index: 0`
and their contents have `z-index: 1`.
`.textLayer` has an explicit `z-index: 0` to introduce a new stacking context,
so that its contents are not drawn on top of `.annotationLayer`.
- Change all possible semi-private methods into properly private ones. Note that this code is old enough to predate standard classes.
- Move the `appendText` helper function into `TextLayerRenderTask`, as a private method, to avoid having to manually pass in the scope.
- Simplify `#layoutText` by directly passing in all necessary data. This is possible after the changes PR 18052.
For images that failed to decode once we want to avoid a pointless round-trip to the main-thread, which could otherwise happen for globally cached images.
- These changes will allow a simpler way of implementing PR 17770.
- The /Lang attribute is fetched lazily, with the first `getTextContent` invocation. Given the existing worker-thread caching, this will thus only need to be done *once* per PDF document (and most PDFs don't included this data).
- This makes the /Lang attribute *directly available* in the `textLayer`, which has the following advantages:
- We don't need to block, and thus delay, overall viewer initialization on fetching it (nor pass it around throughout the viewer).
- Third-party users of the `textLayer` will automatically benefit from this, once we start actually using the /Lang attribute in PR 17770.
*Please note:* This also, importantly, means that the `text` reference-tests will then cover this code (which wouldn't otherwise have been the case).
If a user manually calls `PDFPageView.prototype.update()` with a `drawingDelay`-option then it'll always be necessary to re-call the method *without* a delay afterwards, regardless of the `maxCanvasPixels`-value (e.g. even when CSS-only zooming is used).
This only happens when it's safe to do so. The exceptions are:
- when the class extends another subclass: removing the constructor would remove the error about the missing super() call
- when there are default parameters, that could have side effects
- when there are destructured prameters, that could have side effects
- The `stopAtErrors` API option, which is the inverse of the "internal" `ignoreErrors` option, is explicitly documented as applying to *parsing* (i.e. the worker-thread) while the `FontFaceObject` class is used during rendering (i.e. the main-thread); see b6765403a1/src/display/api.js (L164-L167)
- A glyph that fails in the `FontRendererFactory`, on the worker-thread, will already cause (overall) parsing to stop when `ignoreErrors === false` hence checking the option on the main-thread as well seems redundant; see b6765403a1/src/core/evaluator.js (L4527-L4533)
- Removing this option simplifies the code, and slightly reduces the number of options that we need to handle in the main-thread code.
This avoids having to add a couple of event listeners in the viewer, when debugging is enabled, and is consistent with the existing handling of `FontInspector` and `StepperManager` in the API.
This global was only introduced to work-around problems caused by the GENERIC PDF.js build using top level await. Since that was removed in the previous commit, this global is now dead code.
This limit is currently completely non-functional, since the check happens *after* the entire textLayer has been parsed and appended to the DOM. It seems that this has been *accidentally* broken ever since the introduction of `ReadableStream` support.
The reason that this hasn't caused noticeable textLayer-related performance issues in practice is probably because we nowadays manage to coalesce the textLayer into fewer overall DOM elements, whereas years ago many PDF documents ended up with one DOM element *per* glyph.
By moving this check, and thus restoring the functionality, we're also able to remove the `render` helper function and simplify the code.
The only reason that this code still accepts `TextContent` is for backward-compatibility purposes, so we can simplify the implementation by always using a `ReadableStream` internally.
*Please note:* This removes top level await from the GENERIC builds of the PDF.js library.
Despite top level await being supported in all modern browsers/environments, note [the MDN compatibility data](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/await#browser_compatibility), it seems that many frameworks and build-tools unfortunately have trouble with it.
Hence, in order to reduce the influx of support requests regarding top level await it thus seems that we'll have to try and fix this.
Given that top level await is only needed for Node.js environments, to load packages/polyfills, we re-factor things to limit the asynchronicity to that environment.
The "best" solution, with the least likelihood of causing future problems, would probably be to await the load of Node.js packages/polyfills e.g. at the top of the `getDocument`-function. Unfortunately that doesn't work though, since that's a *synchronous* function that we cannot change without breaking "the world".
Hence we instead await the load of Node.js packages/polyfills together with the `PDFWorker` initialization, since that's the *first point* of asynchronicity during initialization/loading of a PDF document. The reason that this works is that the Node.js packages/polyfills are only needed during fetching of the PDF document respectively during rendering, neither of which can happen *until* the worker has been initialized.
Hopefully this won't cause any future problems, since looking at the history of the PDF.js project I don't believe that we've (thus far) ever needed a Node.js dependency at an earlier point.
This new pattern for accessing Node.js packages/polyfills will also require some care during development *and* importantly reviewing, to ensure that no new top level await is added in the main code-base.
This commit replaces `waitForFunction` calls that use
`document.activeElement` to wait for an element to get focus by simpler
`waitForSelector` expressions that use the `:focus` selector. Note that
we already use this in other tests, so this improves consistency too.
This commit replaces a `waitForTimeout` occurrence with an equivalent
`waitForSelector` expression, and removes two other `waitForTimeout`
occurrences that are obsolete because we already wait for an observable
event to trigger or class change to happen.
Note that the other `waitForTimeout` occurrences in this file are either
part of #17931 or remain until we find a good way to ensure that nothing
happened (because currently there is nothing we can await there).
