From 3e77c1699a843c0512a347cf25938d1f93e715ae Mon Sep 17 00:00:00 2001
From: Olivier Fourdan <ofourdan@redhat.com>
Date: Mon, 27 Nov 2023 13:57:58 +0100
Subject: [PATCH] xwayland: Add helper function for fractional scaling

Fractional scaling may not be available, or not suitable for the current
configuration (e.g. if running rootless).

Add a helper function to tell whether fractional scaling should be used.

Signed-off-by: Olivier Fourdan <ofourdan@redhat.com>
Reviewed-By: Kenny Levinsen <kl@kl.wtf>
Acked-by: Peter Hutterer <peter.hutterer@who-t.net>
Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/1197>
---
 hw/xwayland/xwayland-screen.c | 23 +++++++++++++++++++++++
 hw/xwayland/xwayland-screen.h |  1 +
 2 files changed, 24 insertions(+)

diff --git a/hw/xwayland/xwayland-screen.c b/hw/xwayland/xwayland-screen.c
index 6a0f5a2ef..42c9a0e20 100644
--- a/hw/xwayland/xwayland-screen.c
+++ b/hw/xwayland/xwayland-screen.c
@@ -773,6 +773,26 @@ xwl_screen_lost_focus(struct xwl_screen *xwl_screen)
     }
 }
 
+Bool
+xwl_screen_should_use_fractional_scale(struct xwl_screen *xwl_screen)
+{
+    /* Fullscreen uses a viewport already */
+    if (xwl_screen->fullscreen)
+        return FALSE;
+
+    if (xwl_screen->rootless)
+        return FALSE;
+
+    /* We need both fractional scale and viewporter protocols */
+    if (!xwl_screen->fractional_scale_manager)
+        return FALSE;
+
+    if (!xwl_screen->viewporter)
+        return FALSE;
+
+    return xwl_screen->hidpi;
+}
+
 Bool
 xwl_screen_update_global_surface_scale(struct xwl_screen *xwl_screen)
 {
@@ -780,6 +800,9 @@ xwl_screen_update_global_surface_scale(struct xwl_screen *xwl_screen)
     struct xwl_window *xwl_window;
     int32_t old_scale;
 
+    if (xwl_screen_should_use_fractional_scale(xwl_screen))
+        return FALSE;
+
     if (xwl_screen->rootless)
         return FALSE;
 
diff --git a/hw/xwayland/xwayland-screen.h b/hw/xwayland/xwayland-screen.h
index d2c0865b8..477473eea 100644
--- a/hw/xwayland/xwayland-screen.h
+++ b/hw/xwayland/xwayland-screen.h
@@ -173,5 +173,6 @@ void xwl_surface_damage(struct xwl_screen *xwl_screen,
 int xwl_screen_get_next_output_serial(struct xwl_screen * xwl_screen);
 void xwl_screen_lost_focus(struct xwl_screen *xwl_screen);
 Bool xwl_screen_update_global_surface_scale(struct xwl_screen *xwl_screen);
+Bool xwl_screen_should_use_fractional_scale(struct xwl_screen *xwl_screen);
 
 #endif /* XWAYLAND_SCREEN_H */