This function is required for the commenting feature: the user will be able to click
on a comment in the sidebar and the document will be scrolled accordingly.
This commit is a first step towards #6419, and it can also help with
first compute which ops can affect what is visible in that part of
the page.
This commit adds logic to track operations with their respective
bounding boxes. Only operations that actually cause something to
be rendered have a bounding box and dependencies.
Consider the following example:
```
0. setFillRGBColor
1. beginText
2. showText "Hello"
3. endText
4. constructPath [...] -> eoFill
```
here we have three rendering operations: the showText op (2) and the
path (4). (2) depends on (0), (1) and (3), while (4) only depends on
(0). Both (2) and (4) have a bounding box.
This tracking happens when first rendering a PDF: we then use the
recorded information to optimize future partial renderings of a PDF, so
that we can skip operations that do not affected the PDF area on the
canvas.
All this logic only runs when the new `enableOptimizedPartialRendering`
preference, disabled by default, is enabled.
The bounding boxes and dependencies are also shown in the pdfBug
stepper. When hovering over a step now:
- it highlights the steps that they depend on
- it highlights on the PDF itself the bounding box
The fixed -400px horizontal offset used by
scrollIntoView led to horizontal scroll only moving
part-way right on narrow screens. The highlights near
the right-edge remained party or completely off
screen.
This centres the highlighted match on any viewport width while
clamping the left margin to 20-400px. On very narrow screens
the scrollbar now moves all the way to the right instead of
stopping midway.
This is a precursor to moving the call into a
worker thread to let us use `OffscreenCanvas`. The
current position wouldn't work since we make
transformations to the canvas object after the
getContext call, which isn't allowed for
OffscreenCanvas. Also it isn't allowed to clone or
`transferControlToOffscreen` the canvas after the
`getContext` call.
The shadow was taken into account when computing the bounding box of the section
containing the link and it was making the clip path wrong.
Since the shadow is almost invisible because of the opacity, the yellow color and the clip
we can remove it without causing any visual regressions (and as a side effect it'll avoid
to use resources to compute it when displayed).
The fixed -400px horizontal offset used by
scrollIntoView led to horizontal scroll only moving
part-way right on narrow screens. The highlights near
the right-edge remained party or completely off
screen.
This centres the highlighted match on any viewport width while
clamping the left margin to 20-400px. On very narrow screens
the scrollbar now moves all the way to the right instead of
stopping midway.
