From c5d24e3d94a7c80bc5fc35e2ef5c34b578474588 Mon Sep 17 00:00:00 2001
From: Vlad Zahorodnii <vlad.zahorodnii@kde.org>
Date: Thu, 30 Nov 2023 09:38:02 +0200
Subject: [PATCH] wayland: Fix wl_buffer size for custom cursors

cairo_image_surface_get_width() and cairo_image_surface_get_height()
return the image size that's in the device pixels.

On the other hand, _gdk_wayland_display_create_shm_surface() takes a
surface size in the logical pixels.

Given that _gdk_wayland_display_get_cursor_for_surface() provides the
desired surface size in device pixels, a much bigger shm surface is
created, which then breaks damage tracking code in
gdk_wayland_device_update_window_cursor().

Fixes #6242
---
 gdk/wayland/gdkcursor-wayland.c | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/gdk/wayland/gdkcursor-wayland.c b/gdk/wayland/gdkcursor-wayland.c
index 4314993519..061565f1df 100644
--- a/gdk/wayland/gdkcursor-wayland.c
+++ b/gdk/wayland/gdkcursor-wayland.c
@@ -467,15 +467,24 @@ _gdk_wayland_display_get_cursor_for_surface (GdkDisplay *display,
   cursor->surface.hotspot_x = x;
   cursor->surface.hotspot_y = y;
 
-  cursor->surface.scale = 1;
-
   if (surface)
     {
+      cursor->surface.width = cairo_image_surface_get_width (surface);
+      cursor->surface.height = cairo_image_surface_get_height (surface);
+
       double sx, sy;
       cairo_surface_get_device_scale (surface, &sx, &sy);
       cursor->surface.scale = (int)sx;
-      cursor->surface.width = cairo_image_surface_get_width (surface);
-      cursor->surface.height = cairo_image_surface_get_height (surface);
+
+      while ((cursor->surface.width % cursor->surface.scale != 0) ||
+             (cursor->surface.height % cursor->surface.scale != 0))
+        {
+          g_warning_once (G_STRLOC " cursor image size (%dx%d) not an integer"
+                     "multiple of scale (%d)", cursor->surface.width, cursor->surface.height,
+                     cursor->surface.scale);
+          cursor->surface.scale--;
+        }
+
       cursor->surface.hotspot_x *= sx;
       cursor->surface.hotspot_y *= sx;
     }
@@ -483,12 +492,13 @@ _gdk_wayland_display_get_cursor_for_surface (GdkDisplay *display,
     {
       cursor->surface.width = 1;
       cursor->surface.height = 1;
+      cursor->surface.scale = 1;
     }
 
   cursor->surface.cairo_surface =
     _gdk_wayland_display_create_shm_surface (display_wayland,
-                                             cursor->surface.width,
-                                             cursor->surface.height,
+                                             cursor->surface.width / cursor->surface.scale,
+                                             cursor->surface.height / cursor->surface.scale,
                                              cursor->surface.scale);
 
   buffer = _gdk_wayland_shm_surface_get_wl_buffer (cursor->surface.cairo_surface);