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, 17 insertions, 2 deletions

diff --git a/src/dump.zig b/src/dump.zig
index 89abd995..ff5d2166 100644
--- a/src/dump.zig
+++ b/src/dump.zig
@@ -11,11 +11,11 @@ const log = std.log.scoped(.dump);
 /// pins it for deterministic goldens); else $XDG_DATA_HOME|~/.local/share
 /// /pardes/pardes-<utc>.zon — timestamped so dumps never overwrite each other.
 /// Creates the pardes dir (parents assumed; a failure surfaces at open).
-pub fn outPath(buf: *[1024:0]u8) ?[:0]const u8 {
+pub fn outPath(buf: *[1024:0]u8, dir_setting: []const u8) ?[:0]const u8 {
     if (std.c.getenv("PARDES_DUMP")) |p|
         return std.fmt.bufPrintSentinel(buf, "{s}", .{std.mem.span(p)}, 0) catch null;
     var dir_buf: [900]u8 = undefined;
-    const dir = defaultDirectory(&dir_buf) orelse return null;
+    const dir = directory(&dir_buf, dir_setting) orelse return null;
     var dz: [901:0]u8 = undefined;
     @memcpy(dz[0..dir.len], dir);
     dz[dir.len] = 0;
@@ -32,6 +32,15 @@ pub fn outPath(buf: *[1024:0]u8) ?[:0]const u8 {
         ds.getSecondsIntoMinute(),
     }, 0) catch null;
 }
+/// Where dumps go and relative Restore names are looked up: the `DumpDir`
+/// setting when set (a leading `~/` is the home directory), else the default.
+pub fn directory(buf: []u8, dir_setting: []const u8) ?[]const u8 {
+    if (dir_setting.len == 0) return defaultDirectory(buf);
+    if (std.mem.startsWith(u8, dir_setting, "~/")) if (std.c.getenv("HOME")) |h|
+        return std.fmt.bufPrint(buf, "{s}/{s}", .{ std.mem.span(h), dir_setting[2..] }) catch null;
+    return std.fmt.bufPrint(buf, "{s}", .{dir_setting}) catch null;
+}
+
 /// The standard dump directory, without creating it or generating a filename.
 pub fn defaultDirectory(buf: []u8) ?[]const u8 {
     if (std.c.getenv("XDG_DATA_HOME")) |x|
@@ -69,8 +78,14 @@ pub const PaneKind = enum {
 
 pub const Terminal = struct {
     cwd: []const u8 = "",
+    /// The rendered scrollback and screen as plain text, one row per line.
     stream: []const u8 = "",
     stream_b64: []const u8 = "",
+    /// `stream_b64` is the emulator's primary screen and scrollback as clean
+    /// VT (ghostty's formatter), which replays to what the screen showed.
+    /// Absent (older dumps), it is the raw tail of the pty's output, which
+    /// replays faithfully only if it holds the whole session at one size.
+    stream_is_screen: bool = false,
     cursor: Cursor = .{},
 };