Fixes#10369
When `resizeWithoutReflowGrowCols` copies rows to a previous page with
spare capacity, tracked pins pointing to those rows were not being remapped.
This left pins pointing to the original page which was subsequently destroyed.
The fix adds pin remapping for rows copied to the previous page,
matching the existing remapping logic for rows copied to new pages.
I also added new integrity checks to verify that our tracked pins are
always valid at points where internal operations complete.
Thanks to @grishy for finding this!
This never caused any known issues, but it's a bug! `increaseCapacity`
should produce a node with identical contents, just more capacity. We
were forgetting to copy over the dirty flag.
I looked back at `adjustCapacity` and it also didn't preserve the dirty
flag so presumably downstream consumers have been handling this case
manually. But, I think semantically it makes sense for
`increaseCapacity` to preserve the dirty flag.
This bug was found by AI (while I was doing another task). I fixed it
and wrote the test by hand though.
Fixes#10352
The bug was that non-standard pages would mix the old
`growRequiredForActive` check and make our active area insufficient in
the PageList.
But, since scrollbars now require we have a cached `total_rows` that our
safety checks always verify, we can remove the old linked list traversal
and switch to some simple math in general across all page sizes.
Partial #10227
This fixes the scrollbar part of #10227, but not the search part.
The way PageList works is that max_size is advisory: we always allocate
on page boundaries so we always have _some_ extra space (usually, unless
you ask for a byte-perfect max size). Normally this is fine, it doesn't
cause any real issues.
But with the introduction of scrollbars (and search), we were exposing
this hidden space to the user. To fix this, the easiest approach is to
special-case the zero-scrollback scenario, since it is already
documented that scrollback limit is not _exact_ and is subject to some
minimum allocations. But with zero-scrollback we really expect NOTHING.
Fixes#9958
Replaces #9989
This changes the search navigation logic to always scroll if there is a
selected search result so long as the search result isn't already within
the viewport.
When reflowing content with many graphemes, the code incorrectly increased hyperlink_bytes capacity
instead of grapheme_bytes, causing GraphemeMapOutOfMemory errors.
When columns shrink during resize-without-reflow, page.size.cols is
updated but page.capacity.cols retains the old larger value. When
adjustCapacity later runs (e.g., to expand style/grapheme storage),
it was creating a new page using page.capacity which has the stale
column count, causing size.cols to revert to the old value.
This caused a crash in render.zig where an assertion checks that
page.size.cols matches PageList.cols.
Fix by explicitly copying page.size.cols to the new page after
creation, matching how size.rows is already handled.
Amp-Thread-ID: https://ampcode.com/threads/T-976bc49a-7bfd-40bd-bbbb-38f66fc925ff
Co-authored-by: Amp <amp@ampcode.com>
This removes all existing functionality that I know of that encodes a
terminal, screen, pagelist, or page as plaintext and unifies all logic
onto the formatter system.
Related to #111
This adds the necessary logic and data for the `PageList` data structure
to keep track of **total length** of the screen, **offset** into the
viewport, and **length** of the viewport. These three values are
necessary to _render_ a scrollbar. This PR updates the renderer to grab
this information but stops short of actually drawing a scrollbar (which
we'll do with native UI), in the interest of having a PR that doesn't
contain too many changes.
**This doesn't yet draw a scrollbar, these are just the internal changes
necessary to support it.**
## Background
The `PageList` structure is very core to how we represent terminal
state. It maintains a doubly linked list of "pages" (not literally
virtual memory pages, but close). Each page stores cell information,
styles, hyperlinks, etc fully self-contained in a contiguous sets of VM
pages using offset addresses rather than full pointers. **Pages are not
guaranteed to be equal sizes.** (This is where scrollbars get difficult)
Because it is a linked list structure of non-equal sized nodes, it isn't
amenable to typical scrollbar behavior. A scrollbar needs to know: full
size, offset, and length in order to draw the scrollbar properly.
Getting these values naively is `O(N)` within the data structure that is
on the hottest IO performance path in all of Ghostty.
## Implementation
### PageList
We now maintain two cached values for **total length** and **viewport
offset**.
The total length is relatively straightforward, we just have to be
careful to update it in every operation that could add or remove rows.
I've done this and ensured that every place we update it is covered with
unit test coverage.
The viewport offset is nasty, but I came up with what I believe is a
good solution. The viewport when arbitrarily scrolled is defined as a
direct pointer to the linked list node plus a row offset into that node.
The only way to calculate offset from the top is `O(N)`.
But we have a couple shortcuts:
1. If the viewport is at the bottom (most common) or top, calculating
the offset is `O(1)`: bottom is `total_rows - active_rows`, both readily
available. And top is `0` by definition.
2. Operations on the PageList typically add or remove rows. We don't do
arbitrary linked list surgery. If we instrument those areas with delta
updates to our cache, we can avoid the `O(N)` cost for most operations,
including scrolling a scrollbar. The only expensive operation is a full,
arbitrary jump (new node pointer).
Point 1 was quick to implement, so I focused all the complexity on point
2. Whenever we have an operation that adds or removes rows (for example
pruning the scroll back, adding more, erase rows within the active area,
etc.) then I do the math to calculate the delta change required for the
offset if we've already calculated it, and apply that directly.
### Renderer
The other issue was how to notify the apprts of scrollbar state. Sending
messages on any terminal change within the IO thread is a non-option
because (1) sending messages is slow (2) the terminal changes a lot and
(3) any slowness in the IO thread slows down overall terminal
throughput.
The solution was to **trigger scrollbar notifications with the renderer
vsync**. We read the scrollbar information when we render a frame,
compare it to renderer previous state, and if the scrollbar changed,
send a message to the apprt _after the frame is GPU-renderer_.
The renderer spends _most_ of its time sleeping compared to the IO
thread, and has more opportunities for optimizing its awake time.
Additionally, there's no reason to update the scrollbar information if
the renderer hasn't rendered the new frames because the user can't even
see the stuff the scrollbar wants to scroll to. We're talking about
millisecond scale stuff here at worst but it adds up.
## Performance
No noticeable performance impact for the additional metrics:
<img width="1012" height="738" alt="image"
src="https://github.com/user-attachments/assets/4ed0a3e8-6d76-40c1-b249-e34041c2f6fd"
/>
## AI Usage
I used Amp to help audit the codebase and write tests. I wrote all the
main implementation code manually. I came up with the main design
myself. Relevant threads:
-
https://ampcode.com/threads/T-95fff686-75bb-4553-a2fb-e41fe4cd4b77#message-0-block-0
-
https://ampcode.com/threads/T-48e9a288-b280-4eec-83b7-ca73d029b4ef#message-91-block-0
## Future
This is just the internal changes necessary to _draw_ a scrollbar. There
will be other changes we'll need to add to handle grabbing and actually
jumping the scrollbar. I have a good idea of how to implement those
performantly as well.
- update nixpkgs now that Zig 0.15.2 is available in nixpkgs
- drop hack that worked around compile failures on systems with more
than 32 cores
- enforce patch version of Zig
A whole bunch of inline annotations, some of these were tracked down
with Instruments.app, others are guesses / just seemed right because
they were trivial wrapper functions.
Regardless, these changes are ultimately supported by improved vtebench
results on my machine (Apple M3 Max).
