1 files changed, 38 insertions, 0 deletions
diff --git a/src/panel_animation.zig b/src/panel_animation.zig
index e0cb32d3..a77e5a34 100644
--- a/src/panel_animation.zig
+++ b/src/panel_animation.zig
@@ -116,8 +116,46 @@ pub const Box = extern struct {
     pub fn eql(a: Box, b: Box) bool {
         return a.x == b.x and a.y == b.y and a.w == b.w and a.h == b.h;
     }
+
+    /// Whether a grid cell falls inside this box. Cells are whole, boxes are
+    /// fractional mid-animation, so the test is the cell's ORIGIN against a
+    /// half-open range: a box straddling a column owns it once its origin is
+    /// covered, and never owns it twice.
+    pub fn contains(box: Box, col: u16, row: u16) bool {
+        const x: f32 = @floatFromInt(col);
+        const y: f32 = @floatFromInt(row);
+        return x >= box.x and x < box.x + box.w and y >= box.y and y < box.y + box.h;
+    }
 };
 
+/// The order every backend composites tracks in: moving panes first, then new
+/// panes, then inert closing tombstones on top. Returns how many were written.
+///
+/// A function rather than a loop inside `Pardes.render` because it is a RULE
+/// three hosts used to re-derive — macos.zig re-sorted the already-sorted list
+/// and tty/panel_compositor.zig walked the phases again — and a second sort
+/// that happens to agree is the one that silently stops agreeing. `render`
+/// calls this and every host receives the result verbatim.
+///
+/// Inactive tracks are dropped here, so a host never has to ask.
+pub fn paintOrder(live: []const ?Track, closing: []const Track, out: []Track) usize {
+    var len: usize = 0;
+    for ([_]Phase{ .moving, .opening }) |phase| for (live) |maybe| {
+        const track = maybe orelse continue;
+        if (!track.active() or track.phase != phase) continue;
+        if (len == out.len) return len;
+        out[len] = track;
+        len += 1;
+    };
+    for (closing) |track| {
+        if (!track.active()) continue;
+        if (len == out.len) return len;
+        out[len] = track;
+        len += 1;
+    }
+    return len;
+}
+
 /// One POD record is enough for every backend. `from` and `to` are logical
 /// cell boxes; frontends convert them to pixels only at their render edge.
 pub const Track = extern struct {