The idea is to insert a span in the text layer with an aria-role set to img
and use the bounding box provided by the attribute field in the tag dict in
order to have non-null dimensions for the image to make it "visible".
When selecting text, hovering over an element
causes all the text between (according the the dom
order) the current selection and that element to
be selected.
This means that when, while selecting, the cursor
moves over a link, all the text in the page gets
selected. Setting `user-select: none` on the link
annotations would improve the situation, but it
still makes it impossible to extend the selection
within a link without using Shift+arrows keys on
the keyboard.
This commit fixes the problem by setting
`pointer-events: none` on the `<section>`s in the
annotation layer while selecting some text. This
way, they are ignored for hit-testing and do not
affect selection.
It is still impossible to _start_ a selection
inside a link, as the link text is covered by the
link annotation.
Fixes#18266
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`.
The latest mozilla-central update has test failures, because some CSS variables are not "properly" referenced; in particular:
- Give `--hcm-highlight-selected-filter` a default value, of `none`, similar to the previously existing HCM filter.
- Remove the `--mix-blend-mode` variable, since it's unused.
In order to do that we must change the text layer opacity to 1 but
it has several implications:
- the selection color must have an alpha component,
- the background color of the span used for highlighted words
must have an alpha component either, but now the opacity is 1
we can use some backdrop-filters in HCM making the highlighted
words more visible.
- fix a regression caused by #17196: the css variable --hcm-highlight-filter
has to live under the #viewer element because in HCM it's overwritten
by js at this level, hence links annotations for example didn't
have the right colors when hovered.
The free highlighting is enabled when the mouse pointer isn't on some text.
Then we draw a shape with smoothed borders corresponding to the movement of
the mouse.
Printing/saving and changing the thickness will come later.
Setting the alpha-value explicitly to `1` in `rgb` colors is unnecessary, since that's the default value, and this way we ever so slightly reduce the size of our CSS files.
Unfortunately I've not found a Stylelint rule to enforce this automatically, and the patch was generated using search and replace.
Rather than adding `@media (forced-colors: active) { ... }`-blocks throughout the CSS code, we should utilize CSS variables instead as in our other CSS files.
The idea is just to resuse what we got on the first draw.
Now, we only update the scaleX of the different spans and the other values
are dependant of --scale-factor.
Move some properties in the CSS in order to avoid any updates in JS.
*This is a tentative patch, since we unfortunately cannot easily test it (as far as I can tell).*
In Firefox this (obviously) works as-is, but in Google Chrome the `markedContent` spans are inserted within the regular text-content (in the DOM) and with non-zero heights.
*This is a tentative patch, since I don't have the necessary hardware to test it.*
See https://developer.mozilla.org/en-US/docs/Web/CSS/text-size-adjust, which is currently ignored in Firefox.
It seems overall safer, and more future-proof, to simply add this to the *entire* `textLayer` rather than its individual elements.
When a PDF is "marked" we now generate a separate DOM that represents
the structure tree from the PDF. This DOM is inserted into the <canvas>
element and allows screen readers to walk the tree and have more
information about headings, images, links, etc. To link the structure
tree DOM (which is empty) to the text layer aria-owns is used. This
required modifying the text layer creation so that marked items are
now tracked.
Note that these changes were done automatically, using `gulp lint --fix`.
With this rule, we'll thus enforce a *consistent* formatting of zero-lengths in our CSS files.
Please find additional details about the Stylelint rule at https://stylelint.io/user-guide/rules/length-zero-no-unit
