From 1ab4c071be58033d5452f69797ca8e2c32240cff Mon Sep 17 00:00:00 2001
From: Gabriel Schneider <gbrls@0x4200.cafe>
Date: Tue, 15 Sep 2026 16:28:57 -0300
Subject: Separate tag text geometry from physical pane grips

---
 src/layout.zig | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

(limited to 'src/layout.zig')

diff --git a/src/layout.zig b/src/layout.zig
index 1c43bbd4..f789ba02 100644
--- a/src/layout.zig
+++ b/src/layout.zig
@@ -30,6 +30,7 @@ pub const Presentation = struct {
     pending: bool = false,
     previous_cells: []pardes.Cell = &.{},
     previous_body_layers: [MAX_PANES]pardes.BodyLayer = @splat(.{}),
+    previous_tag_layers: [pardes.MAX_TAG_LAYERS]pardes.TagLayer = @splat(.{}),
     previous_cols: u16 = 0,
     previous_rows: u16 = 0,
     previous_valid: bool = false,
@@ -42,6 +43,7 @@ pub const Presentation = struct {
     pub fn deinit(self: *Presentation, gpa: std.mem.Allocator) void {
         if (self.previous_cells.len > 0) gpa.free(self.previous_cells);
         for (&self.previous_body_layers) |*layer| gpa.free(layer.cells);
+        for (&self.previous_tag_layers) |*layer| gpa.free(layer.cells);
         if (self.diffs.len > 0) gpa.free(self.diffs);
     }
 
@@ -312,6 +314,17 @@ pub const Presentation = struct {
             old.* = current.*;
             old.cells = storage;
         }
+        for (&self.previous_tag_layers, surface.tagLayers()) |*old, *current| {
+            const count = if (current.cols > 0) current.cells.len else 0;
+            const storage = if (old.cells.len == count) old.cells else gpa.realloc(old.cells, count) catch {
+                self.previous_valid = false;
+                self.previous_layout = @splat(null);
+                return;
+            };
+            if (count > 0) @memcpy(storage, current.cells);
+            old.* = current.*;
+            old.cells = storage;
+        }
         @memcpy(self.previous_cells, cells);
         self.previous_cols = surface.cols;
         self.previous_rows = surface.rows;
@@ -550,6 +563,7 @@ pub const Presentation = struct {
         if (self.diff_state == .ready) {
             s.previous_cells = self.previous_cells;
             s.previous_body_layers = &self.previous_body_layers;
+            s.previous_tag_layers = &self.previous_tag_layers;
             s.cell_diffs = self.diffs;
         }
         s.npanel_tracks = paintOrder(
@@ -2103,7 +2117,7 @@ test "fractional panel inverse preserves compact header rows through slide and z
     }
 }
 
-test "presentation snapshots own compact body rows across later edits" {
+test "presentation snapshots own compact body and tag rows across later edits" {
     var state: Presentation = .{};
     defer state.deinit(std.testing.allocator);
     var cells: [1]pardes.Cell = .{.{}};
@@ -2111,12 +2125,18 @@ test "presentation snapshots own compact body rows across later edits" {
     body[0].text[0] = 'A';
     var surface: pardes.Surface = .{ .cols = 1, .rows = 1, .cells = &cells };
     surface.body_layers[0] = .{ .serial = 9, .cols = 1, .rows = 2, .context_rows = 1, .cells = &body };
+    var tag: [1]pardes.Cell = .{.{}};
+    tag[0].text[0] = 'T';
+    surface.tag_layers[0] = .{ .kind = .pane, .serial = 9, .cols = 1, .cells = &tag };
     state.capturePrevious(std.testing.allocator, &surface);
     try std.testing.expect(state.previous_valid);
+    tag[0].text[0] = 'U';
+    try std.testing.expectEqual(@as(u8, 'T'), state.previous_tag_layers[0].cells[0].text[0]);
     body[0].text[0] = 'B';
     surface.body_layers[0].context_rows = 0;
     try std.testing.expectEqual(@as(u8, 'A'), state.previous_body_layers[0].cells[0].text[0]);
     try std.testing.expectEqual(@as(u16, 1), state.previous_body_layers[0].context_rows);
     state.capturePrevious(std.testing.allocator, &surface);
     try std.testing.expectEqual(@as(u8, 'B'), state.previous_body_layers[0].cells[0].text[0]);
+    try std.testing.expectEqual(@as(u8, 'U'), state.previous_tag_layers[0].cells[0].text[0]);
 }
-- 
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