triple-click selects the line (Q#M4, protocol v7)

PointerKind::TripleDown — the cheap additive bump shape returns:
PROTOCOL_VERSION 7, SUPPORTED [6, 7], the new variant kept off
pre-v7 wires by a frontend send-gate that downgrades it to the
plain Down a third click produced before. The GPU's click history
deepens to a chain count (1 → Down, 2 → DoubleDown, 3 →
TripleDown, then restart). Daemon side, select_line_at_cursor
selects the line including its trailing newline, so consecutive
triple-click lines abut.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

pmacs-gpu/src/main.rs

@@ -409,9 +409,11 @@ struct State {
     /// Hit byte of the last Pointer event sent — Drag coalescing:
     /// pixel-rate motion only ships when the hit byte changes.
     last_pointer_sent_byte: Option<u64>,
-    /// `(when, byte)` of the last primary Down, for frontend-side
-    /// double-click detection (same-hit within the interval).
-    last_pointer_down: Option<(std::time::Instant, u64)>,
+    /// `(when, byte, chain_count)` of the last primary Down, for
+    /// frontend-side multi-click detection (same-hit within the
+    /// interval): count 1 = single, 2 = the double already fired,
+    /// so the next same-hit press is a triple (Q#M4).
+    last_pointer_down: Option<(std::time::Instant, u64, u8)>,
     /// Q#R2 — the per-line surgery path skips rebuilding the pointer
     /// hit map (clicks are rare next to keystrokes); this marks it
     /// stale so `hit_test_source_byte` rebuilds on demand from the
@@ -472,6 +474,15 @@ impl App {
         if client.server_protocol_version() < 5 {
             return;
         }
+        // TripleDown is a v7 variant; a pre-v7 instance would
+        // hard-error decoding it. Downgrade to a plain Down — the
+        // exact behavior the third click had before v7 (the chain
+        // restarting).
+        let kind = if kind == PointerKind::TripleDown && client.server_protocol_version() < 7 {
+            PointerKind::Down
+        } else {
+            kind
+        };
         if let Err(e) = client.send_pointer(buffer_id, byte, kind, mods) {
             eprintln!("pmacs-gpu: send_pointer failed: {e}");
         }
@@ -2069,8 +2080,9 @@ impl State {
         self.optimistic_floor_set_at = None;
     }
 
-    /// Frontend-side double-click detection: a second Down at the
-    /// same hit byte within the interval upgrades to `DoubleDown`.
+    /// Frontend-side multi-click detection: a second Down at the
+    /// same hit byte within the interval upgrades to `DoubleDown`,
+    /// a third to `TripleDown` (Q#M4); a fourth restarts the chain.
     fn classify_pointer_down(&mut self, byte: u64, shift: bool) -> PointerKind {
         if shift {
             // Shift-click extends the selection (Q#M5); it neither
@@ -2080,15 +2092,26 @@ impl State {
             return PointerKind::Down;
         }
         let now = std::time::Instant::now();
-        let is_double = self.last_pointer_down.take().is_some_and(|(at, prev)| {
-            prev == byte && now.duration_since(at) <= DOUBLE_CLICK_WINDOW
-        });
-        if is_double {
-            // A third click starts over (triple-click is deferred).
-            PointerKind::DoubleDown
-        } else {
-            self.last_pointer_down = Some((now, byte));
-            PointerKind::Down
+        let prior_chain = self
+            .last_pointer_down
+            .take()
+            .and_then(|(at, prev, count)| {
+                (prev == byte && now.duration_since(at) <= DOUBLE_CLICK_WINDOW).then_some(count)
+            })
+            .unwrap_or(0);
+        match prior_chain {
+            0 => {
+                self.last_pointer_down = Some((now, byte, 1));
+                PointerKind::Down
+            }
+            1 => {
+                self.last_pointer_down = Some((now, byte, 2));
+                PointerKind::DoubleDown
+            }
+            _ => {
+                // Chain consumed: a fourth click starts over.
+                PointerKind::TripleDown
+            }
         }
     }
 

pmacs-protocol/src/message.rs

@@ -352,6 +352,12 @@ pub enum PointerKind {
     /// Second press at the same hit within the frontend's
     /// double-click window — selects the word at `byte`.
     DoubleDown,
+    /// Third press at the same hit within the frontend's
+    /// multi-click window — selects the whole line at `byte`,
+    /// trailing newline included (Q#M4, protocol v7). The frontend
+    /// sends this only to a `>= 7` instance; against an older one
+    /// the third click restarts the chain as a plain `Down`.
+    TripleDown,
 }
 
 impl FrontendEvent {
@@ -1031,7 +1037,14 @@ pub enum ResourceBody {
 /// only v6 peers: a version-mismatched pair fails the handshake with
 /// [`GoodbyeReason::VersionMismatch`] instead of garbling cell
 /// traffic mid-session.
-pub const PROTOCOL_VERSION: u32 = 6;
+///
+/// Q#M4 (mouse deferred set): bumped from 6 to 7 for
+/// [`PointerKind::TripleDown`]. Back to the cheap additive shape:
+/// a new variant on a frontend→instance enum, gated in the frontend
+/// (sent only when the instance's `Hello.protocol_version >= 7`),
+/// so the compat ladder restarts on the v6 encoding floor —
+/// `SUPPORTED_PROTOCOL_VERSIONS` grows to `[6, 7]`.
+pub const PROTOCOL_VERSION: u32 = 7;
 
 /// T M10.5: the set of protocol versions a v1.0 binary accepts on
 /// the wire. v0.1 binaries only accepted `[1]`; v1.0 binaries accept
@@ -1063,7 +1076,12 @@ pub const PROTOCOL_VERSION: u32 = 6;
 /// shared-struct encodings never changed; this bump is the first
 /// that breaks that assumption, and slice membership is how the
 /// handshake communicates it.
-pub const SUPPORTED_PROTOCOL_VERSIONS: &[u32] = &[6];
+///
+/// Q#M4: extended to `[6, 7]`. `PointerKind::TripleDown` is additive
+/// and frontend-gated (like `Pointer` itself at v5), so the ladder
+/// resumes: v6 and v7 binaries interoperate, with the new variant
+/// kept off wires whose instance negotiated `< 7`.
+pub const SUPPORTED_PROTOCOL_VERSIONS: &[u32] = &[6, 7];
 
 /// T M10.5: predicate for the handshake check. Returns `true` if
 /// `peer_version` is in [`SUPPORTED_PROTOCOL_VERSIONS`].

src/editor.rs

@@ -796,6 +796,8 @@ impl EditorState {
     ///   * `Up` collapses an empty selection (a click without drag).
     ///   * `DoubleDown` selects the word at the hit (frontend-side
     ///     double-click detection — only it knows pixel proximity).
+    ///   * `TripleDown` selects the whole line at the hit, trailing
+    ///     newline included (Q#M4, protocol v7).
     ///
     /// The hit byte is clamped into the buffer and snapped back to a
     /// UTF-8 boundary: the frontend's hit may race an in-flight edit.
@@ -862,6 +864,12 @@ impl EditorState {
                 aw.goal_col = None;
                 core.select_word_at_cursor();
             }
+            PointerKind::TripleDown => {
+                let aw = core.active_window_mut();
+                aw.cursor = byte;
+                aw.goal_col = None;
+                core.select_line_at_cursor();
+            }
         }
     }
 
@@ -4452,6 +4460,30 @@ mod tests {
         assert_eq!(s.core.borrow().cursor(), 15, "mismatched buffer ignored");
     }
 
+    #[test]
+    fn dispatch_pointer_triple_down_selects_the_whole_line() {
+        use crate::protocol::{Modifiers as WireMods, PointerKind};
+        // Line 0 = bytes [0, 12) including the newline; line 1 =
+        // [12, 19).
+        let mut s = fresh_with(b"hello world\nsecond\n");
+        let bid = s.core.borrow().active_buffer_id();
+        let none = WireMods::NONE;
+
+        s.dispatch_pointer(FrontendId::LOCAL, bid, 4, PointerKind::TripleDown, none);
+        assert_eq!(
+            s.core.borrow().active_region(),
+            Some((0, 12)),
+            "whole line selected, trailing newline included"
+        );
+        assert_eq!(s.core.borrow().cursor(), 12, "cursor at selection end");
+
+        // A line without a trailing newline runs to the buffer end.
+        let mut s = fresh_with(b"abc");
+        let bid = s.core.borrow().active_buffer_id();
+        s.dispatch_pointer(FrontendId::LOCAL, bid, 1, PointerKind::TripleDown, none);
+        assert_eq!(s.core.borrow().active_region(), Some((0, 3)));
+    }
+
     #[test]
     fn dispatch_pointer_shift_down_extends_instead_of_restarting() {
         use crate::protocol::{Modifiers as WireMods, PointerKind};

src/editor_core.rs

@@ -779,6 +779,30 @@ impl EditorCore {
         true
     }
 
+    /// Select the whole line at the active cursor, trailing newline
+    /// included — the convention that makes consecutive triple-click
+    /// lines abut (Q#M4). The cursor lands at the selection end (the
+    /// start of the next line). No-op when the buffer is gone.
+    pub fn select_line_at_cursor(&mut self) {
+        let id = self.active_buffer_id();
+        let cursor = self.active_window().cursor;
+        let (start, end) = {
+            let reg = self.registry.borrow();
+            let Ok(buffer) = reg.get(id) else {
+                return;
+            };
+            let view = &self.active_window().text_view;
+            let line = view.line_at_offset(cursor);
+            let start = view.line_offset(line).unwrap_or(0);
+            let end = view.line_offset(line + 1).unwrap_or_else(|| buffer.len());
+            (start, end)
+        };
+        let aw = self.active_window_mut();
+        aw.selection = Some(crate::window::Selection { anchor: start });
+        aw.cursor = end;
+        aw.goal_col = None;
+    }
+
     /// Move the cursor forward to the next paragraph break.
     ///
     /// A paragraph break is a blank line (empty or whitespace-only).

src/protocol.rs

@@ -1683,7 +1683,7 @@ mod tests {
     // --- M5.5a handshake & postcard round-trips ---
 
     #[test]
-    fn protocol_version_is_six_for_underline_color() {
+    fn protocol_version_is_seven_for_triple_click() {
         // Pin the value: T M10.5 bumped 1→2 (v1.0 wire: CrdtOp /
         // PresenceUpdate). T M11.1 bumped 2→3 (v1.1 wire: the
         // SemanticFrame family + FrontendEvent::Viewport). T M11.6
@@ -1691,24 +1691,25 @@ mod tests {
         // The mouse framing Q#M1 bumped 4→5 (FrontendEvent::Pointer).
         // T M4.6 bumped 5→6 (`Style::underline_color`) — the first
         // bump that changed an existing struct's postcard encoding,
-        // so v6 binaries serve v6 sessions only.
-        assert_eq!(PROTOCOL_VERSION, 6);
+        // making v6 the ladder's encoding floor. Q#M4 bumped 6→7
+        // (`PointerKind::TripleDown`, additive + frontend-gated).
+        assert_eq!(PROTOCOL_VERSION, 7);
     }
 
     #[test]
-    fn supported_protocol_versions_is_exactly_v6() {
+    fn supported_protocol_versions_resume_ladder_on_v6_floor() {
         // T M4.6: `Style::underline_color` changed the encoding of
-        // every cell-carrying message (`Cell` / `CellDelta` /
-        // `Snapshot` / `StyleSpans`). The v1–v5 compat ladder relied
-        // on shared-struct encodings never changing — additive enum
-        // variants filtered per session — so the ladder ends here:
+        // every cell-carrying message, ending the v1–v5 ladder —
         // pre-v6 peers are refused at the handshake (a clean
         // VersionMismatch) rather than garbling postcard mid-session.
+        // Q#M4: the ladder resumes above that floor — v7 is additive
+        // (`TripleDown`, frontend-gated), so v6 and v7 interoperate.
         assert!(is_supported_protocol_version(6));
-        for rejected in [0, 1, 2, 3, 4, 5, 7, u32::MAX] {
+        assert!(is_supported_protocol_version(7));
+        for rejected in [0, 1, 2, 3, 4, 5, 8, u32::MAX] {
             assert!(
                 !is_supported_protocol_version(rejected),
-                "v{rejected} must be rejected by a v6 binary"
+                "v{rejected} must be rejected by a v7 binary"
             );
         }
     }