1 files changed, 51 insertions, 8 deletions

diff --git a/src/mouse.zig b/src/mouse.zig
index 36786612..1ca53017 100644
--- a/src/mouse.zig
+++ b/src/mouse.zig
@@ -97,13 +97,50 @@ fn cornerFixture(gpa: std.mem.Allocator) !*Pardes {
     return p;
 }
 
+test "a pane's last row of text is no resize handle; the rule over the next pane is" {
+    if (platform == .web) return;
+    const p = try cornerFixture(std.testing.allocator);
+    defer p.deinit();
+    const seam = seamRowOf(p, 1, 0);
+    const inside = p.col_x[1] + p.col_w[1] / 2;
+    p.update(.{ .mouse = .{ .button = .left, .kind = .press, .col = inside, .row = seam } });
+    try std.testing.expect(p.drag != .border_h);
+    p.update(.{ .mouse = .{ .button = .left, .kind = .release, .col = inside, .row = seam } });
+    try std.testing.expect(nudgeRightSeam(p, 2) == seam + 2);
+}
+
+test "a pane's grip dragged up or down its own column moves its top, down to a tag alone above" {
+    if (platform == .web) return;
+    const p = try cornerFixture(std.testing.allocator);
+    defer p.deinit();
+    const upper = p.col_panes[1][0];
+    const lower = p.col_panes[1][1];
+    const grip_x = p.rects[lower].x;
+    // Up, past the pane above's first row: it keeps one row, its tag.
+    const top = p.rects[upper].y;
+    p.update(.{ .mouse = .{ .button = .left, .kind = .press, .col = grip_x, .row = p.rects[lower].y } });
+    p.update(.{ .mouse = .{ .button = .left, .kind = .drag, .col = grip_x, .row = top } });
+    p.update(.{ .mouse = .{ .button = .left, .kind = .release, .col = grip_x, .row = top } });
+    p.sync();
+    try std.testing.expectEqual(@as(u16, 1), p.rects[upper].h);
+    try std.testing.expectEqual(lower, p.col_panes[1][1]);
+    // Down, inside itself: its top follows, the pane above taking the rows.
+    const to = p.rects[lower].y + 6;
+    p.update(.{ .mouse = .{ .button = .left, .kind = .press, .col = grip_x, .row = p.rects[lower].y } });
+    p.update(.{ .mouse = .{ .button = .left, .kind = .drag, .col = grip_x, .row = to } });
+    p.update(.{ .mouse = .{ .button = .left, .kind = .release, .col = grip_x, .row = to } });
+    p.sync();
+    try std.testing.expectEqual(to, p.rects[lower].y);
+}
+
 fn nudgeRightSeam(p: *Pardes, delta: i32) u16 {
     const from = seamRowOf(p, 1, 0);
     const inside = p.col_x[1] + p.col_w[1] / 2;
     const to: u16 = @intCast(@as(i32, from) + delta);
-    p.update(.{ .mouse = .{ .button = .left, .kind = .press, .col = inside, .row = from } });
-    p.update(.{ .mouse = .{ .button = .left, .kind = .drag, .col = inside, .row = to } });
-    p.update(.{ .mouse = .{ .button = .left, .kind = .release, .col = inside, .row = to } });
+    // On the rule a pixel frontend draws over the lower pane's first row.
+    p.update(.{ .mouse = .{ .button = .left, .kind = .press, .col = inside, .row = from + 1, .rule_above = true } });
+    p.update(.{ .mouse = .{ .button = .left, .kind = .drag, .col = inside, .row = to + 1 } });
+    p.update(.{ .mouse = .{ .button = .left, .kind = .release, .col = inside, .row = to + 1 } });
     p.sync();
     return seamRowOf(p, 1, 0);
 }
@@ -437,13 +474,17 @@ pub fn handleMouse(p: *Pardes, m: Mouse) void {
                         return;
                     }
                 }
-                for (0..p.ncol) |cc| {
+                // Two panes are resized on the rule between them, never on a
+                // row of text; with no rule, by the grip, as acme moves a
+                // window by its button.
+                if (m.rule_above and mrow > 0) for (0..p.ncol) |cc| {
                     if (mcol < p.col_x[cc] or mcol >= p.col_x[cc] + p.col_w[cc]) continue;
-                    if (seamIdxAt(p, cc, mrow)) |k| {
-                        p.drag = .{ .border_h = .{ .col = cc, .top_idx = k, .cur_y = mrow } };
+                    const seam = if (p.settings.tag_bottom) mrow else mrow - 1;
+                    if (seamIdxAt(p, cc, seam)) |k| {
+                        p.drag = .{ .border_h = .{ .col = cc, .top_idx = k, .cur_y = seam } };
                         return;
                     }
-                }
+                };
                 const id = hovered orelse return;
                 const r = p.rects[id];
                 const pane = p.panes[id] orelse return;
@@ -597,7 +638,9 @@ pub fn dragUpdate(p: *Pardes, mcol: u16, mrow: u16, body_hit: ?Mouse.BodyHit) vo
             if (k + 1 < p.col_n[cc]) {
                 const a = p.rects[p.col_panes[cc][k]];
                 const b = p.rects[p.col_panes[cc][k + 1]];
-                d.cur_y = clampBorderRow(a.y, a.h, b.h, mrow, p.settings.tag_bottom);
+                // Held by the rule over the lower pane: the seam is the row above.
+                const seam = if (p.settings.tag_bottom) mrow else mrow -| 1;
+                d.cur_y = clampBorderRow(a.y, a.h, b.h, seam, p.settings.tag_bottom);
             } else d.cur_y = mrow;
         },
         .column_move => |*d| d.cur_x = mcol,