From 7d2dd5dee5873fd817c010e73535701e1d647b27 Mon Sep 17 00:00:00 2001

From: Hans de Goede <hdegoede@redhat.com>

Date: Tue, 3 Sep 2019 16:18:00 +0200

Subject: [PATCH 2/2] window-xwayland: Add Xwayland fullscreen games workaround

This is a workaround for X11 games which use randr to change the resolution

in combination with NET_WM_STATE_FULLSCREEN when going fullscreen.

Newer versions of Xwayland support the randr part of this by supporting randr

resolution change emulation in combination with using WPviewport to scale the

app's window (at the emulated resolution) to fill the entire monitor.

Apps using randr in combination with NET_WM_STATE_FULLSCREEN expect the

fullscreen window to have the size of the emulated randr resolution since

when running on regular Xorg the resolution will actually be changed and

after that going fullscreen through NET_WM_STATE_FULLSCREEN will size

the window to be equal to the new resolution.

We need to emulate this behavior for these games to work correctly.

Xwayland's emulated resolution is a per X11 client setting and Xwayland

will set a special _XWAYLAND_RANDR_EMU_MONITOR_RECTS property on the

toplevel windows of a client (and only those of that client), which has

changed the (emulated) resolution through a randr call.

This commit checks for that property and if it is set adjusts the fullscreen

monitor rect for this window to match the emulated resolution.

Here is a step-by-step of such an app going fullscreen:

1. App changes monitor resolution with randr.

2. Xwayland sets the _XWAYLAND_RANDR_EMU_MONITOR_RECTS property on all the

   apps current and future windows. This property contains the origin of the

   monitor for which the emulated resolution is set and the emulated

   resolution.

3. App sets _NET_WM_FULLSCREEN.

4. We check the property and adjust the app's fullscreen size to match

   the emulated resolution.

5. Xwayland sees a Window at monitor origin fully covering the emulated

   monitor resolution. Xwayland sets a viewport making the emulated

   resolution sized window cover the full actual monitor resolution.

https://gitlab.gnome.org/GNOME/mutter/merge_requests/739

---

 src/wayland/meta-window-xwayland.c | 89 ++++++++++++++++++++++++++++++

 src/x11/atomnames.h                |  1 +

 2 files changed, 90 insertions(+)

diff --git a/src/wayland/meta-window-xwayland.c b/src/wayland/meta-window-xwayland.c

index 6f073893a..9967f439a 100644

--- a/src/wayland/meta-window-xwayland.c

+++ b/src/wayland/meta-window-xwayland.c

@@ -20,6 +20,7 @@

 #include "x11/window-x11.h"

 #include "x11/window-x11-private.h"

+#include "x11/xprops.h"

 #include "wayland/meta-window-xwayland.h"

 #include "wayland/meta-wayland.h"

@@ -53,6 +54,93 @@ meta_window_xwayland_init (MetaWindowXwayland *window_xwayland)

 {

 }

+/**

+ * meta_window_xwayland_adjust_fullscreen_monitor_rect:

+ *

+ * This function implements a workaround for X11 apps which use randr to change the

+ * the monitor resolution, followed by setting _NET_WM_FULLSCREEN to make the

+ * window-manager fullscreen them.

+ *

+ * Newer versions of Xwayland support the randr part of this by supporting randr

+ * resolution change emulation in combination with using WPviewport to scale the

+ * app's window (at the emulated resolution) to fill the entire monitor.

+ *

+ * Apps using randr in combination with NET_WM_STATE_FULLSCREEN expect the

+ * fullscreen window to have the size of the emulated randr resolution since

+ * when running on regular Xorg the resolution will actually be changed and

+ * after that going fullscreen through NET_WM_STATE_FULLSCREEN will size

+ * the window to be equal to the new resolution.

+ *

+ * We need to emulate this behavior for these apps to work correctly.

+ *

+ * Xwayland's emulated resolution is a per X11 client setting and Xwayland

+ * will set a special _XWAYLAND_RANDR_EMU_MONITOR_RECTS property on the

+ * toplevel windows of a client (and only those of that client), which has

+ * changed the (emulated) resolution through a randr call.

+ *

+ * Here we check for that property and if it is set we adjust the fullscreen

+ * monitor rect for this window to match the emulated resolution.

+ *

+ * Here is a step-by-step of such an app going fullscreen:

+ * 1. App changes monitor resolution with randr.

+ * 2. Xwayland sets the _XWAYLAND_RANDR_EMU_MONITOR_RECTS property on all the

+ *    apps current and future windows. This property contains the origin of the

+ *    monitor for which the emulated resolution is set and the emulated

+ *    resolution.

+ * 3. App sets _NET_WM_FULLSCREEN.

+ * 4. We check the property and adjust the app's fullscreen size to match

+ *    the emulated resolution.

+ * 5. Xwayland sees a Window at monitor origin fully covering the emulated

+ *    monitor resolution. Xwayland sets a viewport making the emulated

+ *    resolution sized window cover the full actual monitor resolution.

+ */

+static void

+meta_window_xwayland_adjust_fullscreen_monitor_rect (MetaWindow    *window,

+                                                     MetaRectangle *fs_monitor_rect)

+{

+  MetaX11Display *x11_display = window->display->x11_display;

+  MetaRectangle win_monitor_rect;

+  cairo_rectangle_int_t *rects;

+  uint32_t *list = NULL;

+  int i, n_items = 0;

+

+  if (!window->monitor)

+    {

+      g_warning ("MetaWindow does not have a monitor");

+      return;

+    }

+

+  win_monitor_rect = meta_logical_monitor_get_layout (window->monitor);

+

+  if (!meta_prop_get_cardinal_list (x11_display,

+                                    window->xwindow,

+                                    x11_display->atom__XWAYLAND_RANDR_EMU_MONITOR_RECTS,

+                                    &list, &n_items))

+    return;

+

+  if (n_items % 4)

+    {

+      meta_verbose ("_XWAYLAND_RANDR_EMU_MONITOR_RECTS on %s has %d values which is not a multiple of 4",

+                    window->desc, n_items);

+      g_free (list);

+      return;

+    }

+

+  rects = (cairo_rectangle_int_t *) list;

+  n_items = n_items / 4;

+  for (i = 0; i < n_items; i++)

+    {

+      if (rects[i].x == win_monitor_rect.x && rects[i].y == win_monitor_rect.y)

+        {

+          fs_monitor_rect->width = rects[i].width;

+          fs_monitor_rect->height = rects[i].height;

+          break;

+        }

+    }

+

+  g_free (list);

+}

+

 static void

 meta_window_xwayland_force_restore_shortcuts (MetaWindow         *window,

                                               ClutterInputDevice *source)

@@ -115,6 +203,7 @@ meta_window_xwayland_class_init (MetaWindowXwaylandClass *klass)

   MetaWindowClass *window_class = META_WINDOW_CLASS (klass);

   GObjectClass *gobject_class = G_OBJECT_CLASS (klass);

+  window_class->adjust_fullscreen_monitor_rect = meta_window_xwayland_adjust_fullscreen_monitor_rect;

   window_class->force_restore_shortcuts = meta_window_xwayland_force_restore_shortcuts;

   window_class->shortcuts_inhibited = meta_window_xwayland_shortcuts_inhibited;

diff --git a/src/x11/atomnames.h b/src/x11/atomnames.h

index b61f47ff4..4099d5d31 100644

--- a/src/x11/atomnames.h

+++ b/src/x11/atomnames.h

@@ -81,6 +81,7 @@ item(ATOM_PAIR)

 item(_XKB_RULES_NAMES)

 item(WL_SURFACE_ID)

 item(_XWAYLAND_MAY_GRAB_KEYBOARD)

+item(_XWAYLAND_RANDR_EMU_MONITOR_RECTS)

 /* Oddities: These are used, and we need atoms for them,

  * but when we need all _NET_WM hints (i.e. when we're making

-- 

2.23.0