The size of the canvas has significant impact on the rendering
performance. If we are going to render a high-res detail
view on top of the full-page canvas, we can further
reduce the full-page canvas resolution to improve
rendering time without affecting the resolution seen by
the user.
Users will se the lower resolution when quickly scrolling around the
page, but it will then be replaced with the high-res
detail view.
It can happen with a pdf having a large text layer.
Instead of waiting for the first rendered page to enable the buttons we wait for
a rendered annotation editor layer.
In order to see the issue this patch is fixing:
- open a pdf with some highlights and a comment on page 1, at page 7
- open the comment sidebar
- click on the comment on page 1
Opening at page 7 lets a not fully rendered page which means that when jumping to it
with the sidebar, we re-use what we've instead of redrawing it.
This PR changes the way we store bounding boxes so that they use less
memory and can be more easily shared across threads in the future.
Instead of storing the bounding box and list of dependencies for each
operation that renders _something_, we now only store the bounding box
of _every_ operation and no dependencies list. The bounding box of
each operation covers the bounding box of all the operations affected
by it that render something. For example, the bounding box of a
`setFont` operation will be the bounding box of all the `showText`
operations that use that font.
This affects the debugging experience in pdfBug, since now the bounding
box of an operation may be larger than what it renders itself. To help
with this, now when hovering on an operation we also highlight (in red)
all its dependents. We highlight with white stripes operations that do
not affect any part of the page (i.e. with an empty bbox).
To save memory, we now save bounding box x/y coordinates as uint8
rather than float64. This effectively gives us a 256x256 uniform grid
that covers the page, which is high enough resolution for the usecase.
If the document changes the comment state from the old document should
be replaced with that of the new document. To do this the comment
manager is destroyed, but the corresponding comment sidebar wasn't
destroyed yet, which resulted in the comment state from the old document
still being visible for the new document.
This commit fixes the issue by hiding the comment sidebar if the comment
manager is destroyed. Note that hiding the comment sidebar effectively
destroys all its state, and we already set the annotation mode to "none"
on document change so we don't want to keep showing the comment sidebar
anyway.
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.
