We used a SVG string which can be pass to the Path2D ctor but it's a bit slower than
building the path step by step.
Having numerical data instead of a string will help the font data serialization.
The position of the text rendered by `showText` is affected
incrementally by the preceding `showText` operations "on the same line".
For this reason, we keep track of all of them (with their dependencies)
in `sameLineText`.
`sameLineText` can be reset whenever we explicitly position the text
somewhere else. We were previously only doing it for `moveText`, and
this patch updates the code to also do it on `setTextMatrix` (which
resets `this.current.x/y` in `CanvasGraphics` to 0).
The complexity of subsequent `sameLineText` operations dependency
tracking grows quadratically with the number of operations on the same
line, so this patch fixes the performance problem when there are whole
pages of text that only use `setTextMatrix` and not `moveText`.
The `width` and `height` arguments for `setDims` have been removed in
PR #20285, but for two calls in the highlight code they remained. This
commit removes them as they are no longer used in the method itself.
Fixes 0722faa9.
This PR serializes font data into an ArrayBuffer
that is then transfered from the worker to the
main thread. It's more efficient than the current
solution which clones the "export data" object
which includes the font data as a Uint8Array.
It prepares us to switch to a SharedArrayBuffer
in the future, which would allow us to share
the font data with multiple agents, which would be
crucial for the upcoming "renderer" worker.
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.
