One diff-aware expansion for a click, a 9P whole-line look and an empty event write-back; a blank context line resolves to its path:line

The mouse expanded a diff line by its kind (a header or a hunk line's
prefix to the line's address, a hunk line's code to words), but an
empty look written back to event used the plain word expansion, so ML
on a `+` took nothing, and a 9P look of a blank context line (` `) was
refused as whitespace. look.diffClick is now the one answer: the
mouse, the whole-line look and the event write-back all ask it, and a
blank context line is a line like any other. A test asks all three on
each kind of line.

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

1 files changed, 7 insertions, 14 deletions

diff --git a/src/exec.zig b/src/exec.zig
index 104e3b4d..e15ad12c 100644
--- a/src/exec.zig
+++ b/src/exec.zig
@@ -176,21 +176,14 @@ pub fn pointerOperand(p: *Pardes, pane: *Pane, clicked: Pane.Sel) PointerOperand
     // the code's, the prefix never one of them.
     var word_from: usize = 0;
     if (clicked.r0 >= pane.tag_rows and clicked.r0 == clicked.r1 and clicked.c0 == clicked.c1 and row >= 0) diff: {
-        const lines = look.diffLines(p, pane) orelse break :diff;
-        const at: usize = @intCast(row);
-        if (at >= lines.len) break :diff;
-        const line = lines[at];
         var address_buf: [4096 + 32]u8 = undefined;
-        const address = look.diffAddress(pane, lines, at, &address_buf) orelse break :diff;
-        const target = @import("diff.zig").targetAt(lines, at, pane.file == null).?;
-        const on_prefix = col == 0 and line.len > 0 and std.mem.indexOfScalar(u8, "+- ", line[0]) != null;
-        switch (target.kind) {
-            .context, .added, .removed => if (!on_prefix) {
-                word_from = @intFromBool(line.len > 0 and std.mem.indexOfScalar(u8, "+- ", line[0]) != null);
-                break :diff;
-            },
-            else => {},
-        }
+        const at: usize = @intCast(row);
+        const click = look.diffClick(p, pane, at, @intCast(@max(0, col)), &address_buf) orelse break :diff;
+        const address = click.address orelse {
+            word_from = click.word_from;
+            break :diff;
+        };
+        const line = (look.diffLines(p, pane) orelse break :diff)[at];
         result.text = p.scratch.allocator().dupe(u8, address) catch break :diff;
         const hi = std.math.cast(i32, line.len) orelse return result;
         if (hi == 0) return result;