A click that takes no text tells the event reader nothing, and click records are tested for their offsets

Dogfooding saw a body right-click reported as ML0 0 2 3 qty. On file panes
the offsets were right in every case tried here (a scratch made over 9P and
clicked while another pane is active, after a hover, scrolled, soft-wrapped,
tab-indented, inside parentheses); the test now holds them. The 0 0 form
is a terminal's body, which has no offsets to give (its body is a history
snapshot); since the event file now takes a record back whole, such a record
can still be written back and done, and the docs say so. What the test did
find: a click on whitespace sent an empty record, where acme's look3 and
execute return without a word on an empty expansion (look.c:37, exec.c:141).

Co-Authored-By: Claude Opus 5.5 <[email protected]>

2 files changed, 59 insertions, 4 deletions

diff --git a/src/mouse.zig b/src/mouse.zig
index beb2e624..0ec20df2 100644
--- a/src/mouse.zig
+++ b/src/mouse.zig
@@ -715,10 +715,9 @@ fn dispatchPointerBuiltin(
     const arg = p.chord_arg;
     p.chord_arg = null;
     defer if (arg) |a| p.gpa.free(a);
-    const operand = text orelse {
-        if (gesture) |g| _ = reportGesture(p, id, cmd, "", g.on_tag, g.operand, arg != null);
-        return;
-    };
+    // A click that takes no text does nothing, and tells an event reader
+    // nothing, as acme's look3 and execute return on an empty expansion.
+    const operand = text orelse return;
     if (gesture) |g| if (reportGesture(p, id, cmd, operand, g.on_tag, g.operand, arg != null)) return;
     exec.runBuiltin(p, cmd, id, "", exec.withArg(p, operand, arg));
 }
diff --git a/src/ninep/events.zig b/src/ninep/events.zig
index 3f36c65f..9ebb4bc1 100644
--- a/src/ninep/events.zig
+++ b/src/ninep/events.zig
@@ -921,3 +921,59 @@ test "opens of the log share the open records, and a closed one frees its record
     for (handles) |h| _ = call(p, .{ .tag = 5, .op = .release, .node = log, .handle = h });
     for (p.fs.opens) |o| try testing.expect(o.node == 0);
 }
+
+test "a click in the body reports the offsets of the word it takes, so the record can be written back" {
+    const config = @import("../config.zig");
+    const gpa = testing.allocator;
+    const text = "alpha qty beta\n    qty\n\tqty\ndef f(qty): return qty.x\n" ++ "w" ** 100 ++ " qty\n";
+    const p = try withFile(gpa, text);
+    defer p.deinit();
+    // A scratch made over 9P, clicked while another pane has the keyboard.
+    const scratch = try th.newPane(p);
+    _ = wr(p, Node.of(scratch, .body), text);
+    for ([_]u32{ serialOf(p), scratch }) |serial| {
+        const id = p.paneBySerial(serial).?;
+        p.active = p.paneBySerial(if (serial == scratch) serialOf(p) else scratch).?;
+        const event = Node.of(serial, .event);
+        const h = call(p, .{ .tag = 1, .op = .open, .node = event }).reply.handle;
+        var frame = std.heap.ArenaAllocator.init(gpa);
+        defer frame.deinit();
+        _ = try p.render(frame.allocator());
+        const rect = p.rects[id];
+        const x0 = rect.x + config.GUTTER + config.PREFIX_W;
+        const y0 = if (p.settings.tag_bottom) rect.y else rect.y + p.panes[id].?.tag_rows;
+        const tab: u16 = config.tab_width;
+        const Click = struct { x: u16, y: u16, look: []const u8, exec: []const u8, scroll: i32 = 0 };
+        // Where the wrapped line's `qty` landed, as drawn.
+        const surface = try p.render(frame.allocator());
+        var wrap_col: u16 = 0;
+        while (wrap_col < rect.w and !std.mem.eql(u8, surface.at(x0 + wrap_col, y0 + 5).grapheme(), "q")) wrap_col += 1;
+        for ([_]Click{
+            .{ .x = x0 + 7, .y = y0, .look = "ML6 9 0 3 qty\n", .exec = "MX6 9 0 3 qty\n" },
+            .{ .x = x0 + 5, .y = y0 + 1, .look = "ML19 22 0 3 qty\n", .exec = "MX19 22 0 3 qty\n" },
+            .{ .x = x0 + tab + 1, .y = y0 + 2, .look = "ML24 27 0 3 qty\n", .exec = "MX24 27 0 3 qty\n" },
+            .{ .x = x0 + 7, .y = y0 + 3, .look = "ML34 37 0 3 qty\n", .exec = "MX34 37 0 3 qty\n" },
+            // Scrolled a line, the first row shows the second.
+            .{ .x = x0 + 5, .y = y0, .look = "ML19 22 0 3 qty\n", .exec = "MX19 22 0 3 qty\n", .scroll = 1 },
+            // Wrapped: the word on the continuation row.
+            .{ .x = x0 + wrap_col, .y = y0 + 5, .look = "ML154 157 0 3 qty\n", .exec = "MX154 157 0 3 qty\n" },
+        }) |c| for ([_]pardes.Mouse.Button{ config.look_button, config.exec_button }, [_][]const u8{ c.look, c.exec }) |button, want| {
+            // The pointer rests on the word first, as a hand's does, and
+            // the hover preview comes up under it.
+            p.panes[id].?.scrollBy(c.scroll);
+            _ = try p.render(frame.allocator());
+            p.update(.{ .mouse = .{ .button = .none, .kind = .motion, .col = c.x, .row = c.y } });
+            for (0..200) |_| p.update(.tick);
+            p.update(.{ .mouse = .{ .button = button, .kind = .press, .col = c.x, .row = c.y } });
+            p.update(.{ .mouse = .{ .button = button, .kind = .release, .col = c.x, .row = c.y } });
+            try testing.expectEqualStrings(want, call(p, .{ .tag = 2, .op = .read, .node = event, .handle = h, .size = 256 }).bytes);
+            p.panes[id].?.scrollBy(-c.scroll);
+        };
+        // A click on nothing expands to nothing, and acme then says
+        // nothing (look.c:37, exec.c:141).
+        p.update(.{ .mouse = .{ .button = config.look_button, .kind = .press, .col = x0 + 60, .row = y0 + 1 } });
+        p.update(.{ .mouse = .{ .button = config.look_button, .kind = .release, .col = x0 + 60, .row = y0 + 1 } });
+        try testing.expectEqual(Status.again, call(p, .{ .tag = 2, .op = .read, .node = event, .handle = h, .size = 256 }).reply.status);
+        _ = call(p, .{ .tag = 3, .op = .release, .node = event, .handle = h });
+    }
+}