xwayland: Set _XWAYLAND_RANDR_EMU_MONITOR_RECTS property for resolution emulation

Apps using randr to change the resolution when going fullscreen, in
combination with _NET_WM_STATE_FULLSCREEN to tell the window-manager (WM)
to make their window fullscreen, expect the WM to give the fullscreen window
the size of the emulated resolution as would happen when run under Xorg (*).

We need the WM to emulate this behavior for these apps to work correctly,
with Xwaylands resolution change emulation. For the WM to emulate this,
it needs to know about the emulated resolution for the Windows owning
client for each monitor.

This commit adds a _XWAYLAND_RANDR_EMU_MONITOR_RECTS property, which
contains 4 Cardinals (32 bit integers) per monitor with resolution
emulation info. Window-managers can use this to get the emulated
resolution for the client and size the window correctly.

*) Since under 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.

Reviewed-by: Olivier Fourdan <ofourdan@redhat.com>
Acked-by: Michel Dänzer <mdaenzer@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

hw/xwayland/xwayland-output.c

@@ -29,6 +29,7 @@
 
 #include "xwayland.h"
 #include <randrstr.h>
+#include <X11/Xatom.h>
 
 #define DEFAULT_DPI 96
 #define ALL_ROTATIONS (RR_Rotate_0   | \
@@ -428,6 +429,80 @@ xwl_output_find_mode(struct xwl_output *xwl_output,
     return NULL;
 }
 
+struct xwl_output_randr_emu_prop {
+    Atom atom;
+    uint32_t rects[XWL_CLIENT_MAX_EMULATED_MODES][4];
+    int rect_count;
+};
+
+static void
+xwl_output_randr_emu_prop(struct xwl_screen *xwl_screen, ClientPtr client,
+                          struct xwl_output_randr_emu_prop *prop)
+{
+    static const char atom_name[] = "_XWAYLAND_RANDR_EMU_MONITOR_RECTS";
+    struct xwl_emulated_mode *emulated_mode;
+    struct xwl_output *xwl_output;
+    int index = 0;
+
+    prop->atom = MakeAtom(atom_name, strlen(atom_name), TRUE);
+
+    xorg_list_for_each_entry(xwl_output, &xwl_screen->output_list, link) {
+        emulated_mode = xwl_output_get_emulated_mode_for_client(xwl_output, client);
+        if (!emulated_mode)
+            continue;
+
+        prop->rects[index][0] = xwl_output->x;
+        prop->rects[index][1] = xwl_output->y;
+        prop->rects[index][2] = emulated_mode->width;
+        prop->rects[index][3] = emulated_mode->height;
+        index++;
+    }
+
+    prop->rect_count = index;
+}
+
+static void
+xwl_output_set_randr_emu_prop(WindowPtr window,
+                              struct xwl_output_randr_emu_prop *prop)
+{
+    if (!xwl_window_is_toplevel(window))
+        return;
+
+    if (prop->rect_count) {
+        dixChangeWindowProperty(serverClient, window, prop->atom,
+                                XA_CARDINAL, 32, PropModeReplace,
+                                prop->rect_count * 4, prop->rects, TRUE);
+    } else {
+        DeleteProperty(serverClient, window, prop->atom);
+    }
+}
+
+static void
+xwl_output_set_randr_emu_prop_callback(void *resource, XID id, void *user_data)
+{
+    xwl_output_set_randr_emu_prop(resource, user_data);
+}
+
+static void
+xwl_output_set_randr_emu_props(struct xwl_screen *xwl_screen, ClientPtr client)
+{
+    struct xwl_output_randr_emu_prop prop = {};
+
+    xwl_output_randr_emu_prop(xwl_screen, client, &prop);
+    FindClientResourcesByType(client, RT_WINDOW,
+                              xwl_output_set_randr_emu_prop_callback, &prop);
+}
+
+void
+xwl_output_set_window_randr_emu_props(struct xwl_screen *xwl_screen,
+                                      WindowPtr window)
+{
+    struct xwl_output_randr_emu_prop prop = {};
+
+    xwl_output_randr_emu_prop(xwl_screen, wClient(window), &prop);
+    xwl_output_set_randr_emu_prop(window, &prop);
+}
+
 void
 xwl_output_set_emulated_mode(struct xwl_output *xwl_output, ClientPtr client,
                              RRModePtr mode, Bool from_vidmode)
@@ -442,6 +517,8 @@ xwl_output_set_emulated_mode(struct xwl_output *xwl_output, ClientPtr client,
         xwl_output_add_emulated_mode_for_client(xwl_output, client, mode, from_vidmode);
 
     xwl_screen_check_resolution_change_emulation(xwl_output->xwl_screen);
+
+    xwl_output_set_randr_emu_props(xwl_output->xwl_screen, client);
 }
 
 static void

hw/xwayland/xwayland.c

@@ -720,6 +720,27 @@ xwl_screen_check_resolution_change_emulation(struct xwl_screen *xwl_screen)
         xwl_window_check_resolution_change_emulation(xwl_window);
 }
 
+/* This checks if the passed in Window is a toplevel client window, note this
+ * returns false for window-manager decoration windows and returns true for
+ * the actual client top-level window even if it has been reparented to
+ * a window-manager decoration window.
+ */
+Bool
+xwl_window_is_toplevel(WindowPtr window)
+{
+    struct xwl_screen *xwl_screen = xwl_screen_get(window->drawable.pScreen);
+
+    if (xwl_screen_client_is_window_manager(xwl_screen, wClient(window)))
+        return FALSE;
+
+    /* CSD and override-redirect toplevel windows */
+    if (window_get_damage(window))
+        return TRUE;
+
+    /* Normal toplevel client windows, reparented to decoration window */
+    return (window->parent && window_get_damage(window->parent));
+}
+
 static void
 xwl_window_init_allow_commits(struct xwl_window *xwl_window)
 {
@@ -881,6 +902,8 @@ xwl_realize_window(WindowPtr window)
             return FALSE;
     }
 
+    xwl_output_set_window_randr_emu_props(xwl_screen, window);
+
     return ensure_surface_for_window(window);
 }
 

hw/xwayland/xwayland.h

@@ -414,6 +414,7 @@ Bool xwl_screen_has_resolution_change_emulation(struct xwl_screen *xwl_screen);
 struct xwl_output *xwl_screen_get_first_output(struct xwl_screen *xwl_screen);
 void xwl_screen_check_resolution_change_emulation(struct xwl_screen *xwl_screen);
 Bool xwl_window_has_viewport_enabled(struct xwl_window *xwl_window);
+Bool xwl_window_is_toplevel(WindowPtr window);
 
 void xwl_tablet_tool_set_cursor(struct xwl_tablet_tool *tool);
 void xwl_seat_set_cursor(struct xwl_seat *xwl_seat);
@@ -452,6 +453,8 @@ RRModePtr xwl_output_find_mode(struct xwl_output *xwl_output,
 void xwl_output_set_emulated_mode(struct xwl_output *xwl_output,
                                   ClientPtr client, RRModePtr mode,
                                   Bool from_vidmode);
+void xwl_output_set_window_randr_emu_props(struct xwl_screen *xwl_screen,
+                                           WindowPtr window);
 
 RRModePtr xwayland_cvt(int HDisplay, int VDisplay,
                        float VRefresh, Bool Reduced, Bool Interlaced);