From 20185fc317db5d85f0c5b3d88a22bf3c493102df Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Fri, 1 May 2026 15:04:46 +0000
Subject: [PATCH 1/2] Fix display corruption when maximizing horizontal split
 with window_padding_width >= 4 (issue #9946)

Agent-Logs-Url: https://github.com/kovidgoyal/kitty/sessions/3b0c9eab-24ba-4934-a941-be477477cee4

Co-authored-by: kovidgoyal <1308621+kovidgoyal@users.noreply.github.com>
---
 kitty/layout/base.py  |  6 +++---
 kitty_tests/layout.py | 18 +++++++++++++++++-
 2 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/kitty/layout/base.py b/kitty/layout/base.py
index 6deb610d2..cb957a1f0 100644
--- a/kitty/layout/base.py
+++ b/kitty/layout/base.py
@@ -117,14 +117,14 @@ def layout_dimension(
     bias: None | Sequence[float] | dict[int, float] = None
 ) -> LayoutDimension:
     number_of_windows = len(decoration_pairs)
-    number_of_cells = length // cell_length
+    number_of_cells = max(0, length // cell_length)
     dec_vals: Iterable[int] = map(sum, decoration_pairs)
     space_needed_for_decorations = sum(dec_vals)
     extra = length - number_of_cells * cell_length
-    while extra < space_needed_for_decorations:
+    while extra < space_needed_for_decorations and number_of_cells > 0:
         number_of_cells -= 1
         extra = length - number_of_cells * cell_length
-    cells_map = calculate_cells_map(bias, number_of_windows, number_of_cells)
+    cells_map = calculate_cells_map(bias, number_of_windows, number_of_cells) if number_of_cells > 0 else [0] * number_of_windows
     assert sum(cells_map) == number_of_cells
 
     extra = length - number_of_cells * cell_length - space_needed_for_decorations
diff --git a/kitty_tests/layout.py b/kitty_tests/layout.py
index cbcad2a0c..517ad5fd7 100644
--- a/kitty_tests/layout.py
+++ b/kitty_tests/layout.py
@@ -3,7 +3,7 @@
 
 from kitty.config import defaults
 from kitty.fast_data_types import BOTTOM_EDGE, LEFT_EDGE, RIGHT_EDGE, TOP_EDGE, Region
-from kitty.layout.base import lgd
+from kitty.layout.base import layout_dimension, lgd
 from kitty.layout.interface import Grid, Horizontal, Splits, Stack, Tall
 from kitty.layout.splits import Pair
 from kitty.types import WindowGeometry
@@ -325,6 +325,22 @@ class TestLayout(BaseTest):
         self.assertTrue(result)
         self.ae(root.bias, root_bias_before)
 
+    def test_layout_dimension_no_negative_cells(self):
+        # Regression test for issue #9946: when window padding exceeds the
+        # available space (e.g. after maximize sets a window to minimum width),
+        # layout_dimension must not produce a negative cells_per_window value
+        # which would cause right < left in the resulting window geometry.
+        for length, cell_length, decs in (
+            (8, 8, [(5, 5)]),   # padding (10) > length (8) > cell_length (8)
+            (6, 8, [(4, 4)]),   # length < cell_length
+            (0, 8, [(4, 4)]),   # zero length
+            (4, 8, [(3, 3)]),   # space_needed == length, no room for cells
+        ):
+            result = next(layout_dimension(0, length, cell_length, decs))
+            self.assertGreaterEqual(result.cells_per_window, 0,
+                f'cells_per_window={result.cells_per_window} < 0 for length={length}, '
+                f'cell_length={cell_length}, decs={decs}')
+
     def test_drag_resize_target_windows(self):
         # Helper: call drag_resize_target_windows with given window and edge flags.
         def drtw(q, all_windows, window, edges):

From 4d55d306146ada0792fadb11cd41c43113491f41 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Fri, 1 May 2026 15:05:34 +0000
Subject: [PATCH 2/2] Enhance regression test with additional geometry validity
 assertions

Agent-Logs-Url: https://github.com/kovidgoyal/kitty/sessions/3b0c9eab-24ba-4934-a941-be477477cee4

Co-authored-by: kovidgoyal <1308621+kovidgoyal@users.noreply.github.com>
---
 kitty_tests/layout.py | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/kitty_tests/layout.py b/kitty_tests/layout.py
index 517ad5fd7..fb0802c3f 100644
--- a/kitty_tests/layout.py
+++ b/kitty_tests/layout.py
@@ -340,6 +340,14 @@ class TestLayout(BaseTest):
             self.assertGreaterEqual(result.cells_per_window, 0,
                 f'cells_per_window={result.cells_per_window} < 0 for length={length}, '
                 f'cell_length={cell_length}, decs={decs}')
+            self.assertGreaterEqual(result.content_size, 0,
+                f'content_size={result.content_size} < 0 for length={length}, '
+                f'cell_length={cell_length}, decs={decs}')
+            # content_pos must be within [0, length]: right edge = content_pos + content_size <= length
+            self.assertGreaterEqual(result.content_pos, 0)
+            self.assertLessEqual(result.content_pos + result.content_size, length,
+                f'right ({result.content_pos + result.content_size}) > length ({length}) for '
+                f'cell_length={cell_length}, decs={decs}')
 
     def test_drag_resize_target_windows(self):
         # Helper: call drag_resize_target_windows with given window and edge flags.