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, 19 insertions, 0 deletions

diff --git a/build.zig b/build.zig
index 562ed89f..7010c863 100644
--- a/build.zig
+++ b/build.zig
@@ -142,6 +142,7 @@ pub fn build(b: *std.Build) void {
     const mupdf_check = b.step("mupdf-check", "compile, link, render, and search docs/design.pdf with MuPDF");
     const pdf_bench_step = b.step("pdf-bench", "benchmark real MuPDF page rendering (-- [--json] [--reps N] [--warmup N] [--path FILE] [--page N] [--pages N])");
     const pdf_sections_bench_step = b.step("pdf-sections-bench", "benchmark PDF outline/sections paths in ReleaseFast (-Doptimize=ReleaseFast -- [--json] [--reps N] [--warmup N])");
+    const pdf_pointer_bench_step = b.step("pdf-pointer-bench", "time PDF hover and selection gestures and prove their pixels (-Doptimize=ReleaseFast -- [--label L] [--reps N] [--path FILE] [--cell WxH])");
     const pdf_scroll_bench_step = b.step("pdf-scroll-bench", "benchmark fast continuous-strip PDF scrolling in ReleaseFast (-Doptimize=ReleaseFast -- [--json] [--reps N] [--warmup N] [--path FILE])");
     if (!enable_mupdf)
         mupdf_check.dependOn(&b.addFail("mupdf-check is unavailable with -Dmupdf=false").step);
@@ -151,6 +152,8 @@ pub fn build(b: *std.Build) void {
         pdf_sections_bench_step.dependOn(&b.addFail("pdf-sections-bench is unavailable with -Dmupdf=false").step);
     if (!enable_mupdf)
         pdf_scroll_bench_step.dependOn(&b.addFail("pdf-scroll-bench is unavailable with -Dmupdf=false").step);
+    if (!enable_mupdf)
+        pdf_pointer_bench_step.dependOn(&b.addFail("pdf-pointer-bench is unavailable with -Dmupdf=false").step);
 
     const shaders_step = b.step("shaders", "refresh paired shaders/prebuilt/*.spv + *.glsl snapshots (glslc)");
     const update_shaders = b.addUpdateSourceFiles();
@@ -482,6 +485,22 @@ pub fn build(b: *std.Build) void {
             run_pdf_sections_bench.setCwd(b.path("."));
             pdf_sections_bench_step.dependOn(&run_pdf_sections_bench.step);
 
+            const pdf_pointer_bench = b.addExecutable(.{
+                .name = "pardes-pdf-pointer-bench",
+                .root_module = b.createModule(.{
+                    .target = target,
+                    .optimize = .ReleaseFast,
+                    .root_source_file = b.path("test/pdf_pointer_bench.zig"),
+                    .link_libc = true,
+                }),
+            });
+            pdf_pointer_bench.root_module.addImport("pardes", core_module);
+            pdf_pointer_bench.root_module.addImport("mupdf", mupdf_mod);
+            const run_pdf_pointer_bench = b.addRunArtifact(pdf_pointer_bench);
+            if (b.args) |args| run_pdf_pointer_bench.addArgs(args);
+            run_pdf_pointer_bench.setCwd(b.path("."));
+            pdf_pointer_bench_step.dependOn(&run_pdf_pointer_bench.step);
+
             const pdf_scroll_bench = b.addExecutable(.{
                 .name = "pardes-pdf-scroll-bench",
                 .root_module = b.createModule(.{