From a2283c822971cc22db01a6702408aa69e0510448 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Ekl=C3=B6f?= <daniel@ekloef.se>
Date: Tue, 9 Jan 2024 16:47:41 +0100
Subject: [PATCH] wayland: surface_scale_explicit_width_height(): dont assert
 width/height are valid for scale, take 2

764248bb0d846f65c20931024c1f4adca57aae29 modified
wayl_surface_scale_explicit_width_height() to not assert the surface
size is valid for the given scaling factor. This, since that function
is only used when scaling a mouse pointer surface.

However, that commit only updated the code path run when fractional
scaling is available (i.e. when the compositor implements the
fractional-scale-v1 protocol).

The legacy code path, that does integer scaling, was still asserting
the surface width/height were divisible with the scaling factor.

For the same reasons this isn't true with fractional scaling
available, it's not true with integer scaling. Fix by skipping the
assertions.

This patch also converts the assertions to more verbose BUG() calls,
that prints more information on the numbers involved.

Closes #1573
---
 CHANGELOG.md |  4 ++++
 wayland.c    | 15 ++++++++++++---
 2 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index f25814b8..6c4f998d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -77,8 +77,12 @@
 * config: improved validation of color values.
 * config: double close of file descriptor, resulting in a chain of
   errors ultimately leading to a startup failure ([#1531][1531]).
+* Crash when using a desktop scaling factor > 1, on compositors that
+  implements neither the `fractional-scale-v1`, nor the
+  `cursor-shape-v1` Wayland protocols ([#1573][1573]).
 
 [1531]: https://codeberg.org/dnkl/foot/issues/1531
+[1573]: https://codeberg.org/dnkl/foot/issues/1573
 
 
 ### Security
diff --git a/wayland.c b/wayland.c
index a87bf45d..34050d18 100644
--- a/wayland.c
+++ b/wayland.c
@@ -2024,10 +2024,19 @@ surface_scale_explicit_width_height(
                 "(width=%d, height=%d)", scale, width, height);
 
         xassert(scale == floorf(scale));
-
         const int iscale = (int)floorf(scale);
-        xassert(width % iscale == 0);
-        xassert(height % iscale == 0);
+
+        if (verify) {
+            if (width % iscale != 0) {
+                BUG("width=%d is not valid with scaling factor %.2f (%d %% %d != 0)",
+                    width, scale, width, iscale);
+            }
+
+            if (height % iscale != 0) {
+                BUG("height=%d is not valid with scaling factor %.2f (%d %% %d != 0)",
+                    height, scale, height, iscale);
+            }
+        }
 
         wl_surface_set_buffer_scale(surf->surf, iscale);
     }