client: Avoid protocol error with invalid min/max size

If the application sets an invalid minimum and maximum size
(where the minimum is higher than the maximum), then we
would blindly send this over the protocol, which is a protocol
error according to the spec. Qt compositors will warn about
this and ignore the size, but mainly because "but there's no
matching error defined" according to the comment. Other
compositors may close the connection when this happens.

To avoid crashing the app based on bogus min/max size, we
make sure we never send a maximum size which is less than
the minimum size. This corresponds to the behavior of
compositors which accept the size without raising an error:
the minimum size takes precedence.

Note that 0 means "no maximum size" in the protocol, so we
cap the value before applying this logic.

[ChangeLog][Client] Fixed an issue where setting an invalid
minimum and maximum size on a window would cause some
compositors to raise a protocol error.

Pick-to: 6.2 6.3
Fixes: QTBUG-102626
Fixes: QTBUG-103391
Change-Id: I4004a4550a9fe3dae6a27169b4d1a9a616e21841
Reviewed-by: David Edmundson <davidedmundson@kde.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/src/plugins/shellintegration/xdg-shell/qwaylandxdgshell.cpp b/src/plugins/shellintegration/xdg-shell/qwaylandxdgshell.cpp
index 4603ec11d..c07373f69 100644
--- a/src/plugins/shellintegration/xdg-shell/qwaylandxdgshell.cpp
+++ b/src/plugins/shellintegration/xdg-shell/qwaylandxdgshell.cpp
@@ -391,10 +391,10 @@ void QWaylandXdgSurface::setSizeHints()
         const int minHeight = qMax(0, m_window->windowMinimumSize().height());
         m_toplevel->set_min_size(minWidth, minHeight);
 
-        int maxWidth = qMax(0, m_window->windowMaximumSize().width());
+        int maxWidth = qMax(minWidth, m_window->windowMaximumSize().width());
         if (maxWidth == QWINDOWSIZE_MAX)
             maxWidth = 0;
-        int maxHeight = qMax(0, m_window->windowMaximumSize().height());
+        int maxHeight = qMax(minHeight, m_window->windowMaximumSize().height());
         if (maxHeight == QWINDOWSIZE_MAX)
             maxHeight = 0;
         m_toplevel->set_max_size(maxWidth, maxHeight);