Repaint PDF highlights by row, send rasters by shared memory, and animate messages

PDF highlights (hover preview, search, selection) are baked into page rasters,
and any change re-rendered the whole page with MuPDF; the TTY then re-sent it
as base64 (4.7 MB a page), the GUI as a new texture. Worse, a pointer motion
over a PDF invalidated the page even when no preview was shown, so every
motion paid that. Now:

- A raster whose baked highlight set equals the wanted one is left alone.
- A highlighted page keeps its clean rows (before highlights and tint); a
  change repaints only the rows of quads that differ, running MuPDF's
  highlight pass (pardes_pdf_paint_highlights) over those clean rows and
  tinting them: the operations a full render performs, so the pixels are
  identical. MuPDF band renders are NOT bit-identical to a whole page (edge
  rows, resampled images), so they are never used to patch; the comment
  claiming otherwise is corrected.
- ImagePlace.patch hands shells the changed rows; the GUI uploads just those
  rows into the texture it holds.
- The TTY probes kitty shared memory (t=s) with an id vaxis never reaches and
  sends rasters as a /dev/shm name when the terminal reads it; direct base64
  otherwise (ssh).
- Shells that take row patches (GUI, TTY with shm) repaint a selection while
  it is dragged instead of only on release.

Latency elsewhere:
- TTY: an animating frame no longer sleeps 16 ms blind; a tick thread posts
  into the input queue, so input inside the frame is handled at once.
- TTY and GUI: queued pointer motions coalesce to the last.
- GUI: a skipped swapchain image re-arms the frame (3 retries); animations
  still tick while nothing presents.
- Editing: the line index is carried across an edit instead of rebuilt from
  a scan of the whole file per keystroke.

Messages fall into their row (ease-in; the GUI slides the band out from under
the tagline, a terminal fades it), stay until the next input as before, linger
MessageLinger ms (default 800), and dissolve (ease-out). MessageAnimation
toggles it; both are settings, in Config and startup files. The snapshot
harness pins the old behaviour. The detached server now ticks animations.

A restored terminal comes back live: the old screen and scrollback (dumped
as clean VT by ghostty's formatter, replayed at the new size; older dumps
fall back to their rendered text), a dim
"restored history" marker, then a new shell in the directory it was in.

Right-click on a line number in a file pane looks at that line (a sticky
context header's number included).

Measured with an external pty driver (TTY), an in-process fence trace
(GUI, PARDES_TEST_LATENCY), and test/pdf_pointer_bench.zig (pixel identity
against the baseline and a whole-page oracle); balanced A/A/B rounds, paired
per-round statistics.

Messages stack: each event gets its own row and its own fall, linger and
dissolve; a line keeps its row until it leaves and a new one fills the first
free row. Announcements and statuses are replaced in place, not stacked.
MessageFall, MessageDissolve and DumpDir are settings Config reports.

Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>

1 files changed, 4 insertions, 0 deletions

diff --git a/src/tag_layer.zig b/src/tag_layer.zig
index 0fb2297d..f8cc6eca 100644
--- a/src/tag_layer.zig
+++ b/src/tag_layer.zig
@@ -26,6 +26,10 @@ pub const Layer = struct {
     bg: [3]u8 = .{ 0, 0, 0 },
     cells: []pardes.Cell = &.{},
     cursor: ?struct { col: u16, bar: bool = false } = null,
+    /// Vertical offset in rows (negative: above its viewport), for a band
+    /// that is moving into place. A pixel shell draws it offset and clipped
+    /// to the rows below the viewport's top; the grid has no such thing.
+    slide: f32 = 0,
 
     pub fn capacity(layer: *const Layer, metrics: pardes.RowMetrics) u16 {
         return @intCast(@min(std.math.maxInt(u16), @max(1, @as(u32, layer.viewport.w) * @max(1, metrics.body_w) / @max(1, metrics.tagline_w))));