[mutter/gnome-3-38] wayland/window: Don't lose precision in MetaWaylandWindowConfiguration

[Jonas Ådahl <jadahl src gnome org>]

commit 01e2a54f3358c3ff50c583585cffa53f725bee3d
Author: Jonas Ådahl <jadahl gmail com>
Date:   Thu Oct 29 10:11:15 2020 +0100

    wayland/window: Don't lose precision in MetaWaylandWindowConfiguration
    
    Commit 8bdd2aa7 would offset the window position by the difference
    between the configured window size and the committed size from the
    client to prevent the window from drifting while resizing.
    
    This, however, did not take into account the actual geometry scale, so
    when using any scale greater than 1, the window would rapidly drift away
    due to that offset.
    
    In order to solve this, we need to make sure we store away the pending
    window configuration in the stage coordinate space, in order to not
    loose precision. When we then calculate the offset given the result from
    the client, it'll use the right scalars, while before, one scalar was in
    surface coordinates, while the other in stage coordinates.
    
    https://gitlab.gnome.org/GNOME/mutter/-/issues/1490
    (cherry picked from commit eaa6efef56d3a251e864c7064d7c6ad5d1329c78)

 src/wayland/meta-wayland-legacy-xdg-shell.c     |  7 ++++---
 src/wayland/meta-wayland-window-configuration.c |  8 +++++++-
 src/wayland/meta-wayland-window-configuration.h |  5 ++++-
 src/wayland/meta-wayland-wl-shell.c             |  3 ++-
 src/wayland/meta-wayland-xdg-shell.c            | 13 ++++++++-----
 src/wayland/meta-window-wayland.c               | 11 ++++++++---
 6 files changed, 33 insertions(+), 14 deletions(-)
---
diff --git a/src/wayland/meta-wayland-legacy-xdg-shell.c b/src/wayland/meta-wayland-legacy-xdg-shell.c
index c9c0df6e6e..926ee14e32 100644
--- a/src/wayland/meta-wayland-legacy-xdg-shell.c
+++ b/src/wayland/meta-wayland-legacy-xdg-shell.c
@@ -609,8 +609,8 @@ meta_wayland_zxdg_toplevel_v6_send_configure (MetaWaylandZxdgToplevelV6      *xd
   fill_states (&states, window);
 
   zxdg_toplevel_v6_send_configure (xdg_toplevel->resource,
-                                   configuration->width,
-                                   configuration->height,
+                                   configuration->width / configuration->scale,
+                                   configuration->height / configuration->scale,
                                    &states);
   wl_array_release (&states);
 
@@ -1075,7 +1075,8 @@ meta_wayland_zxdg_popup_v6_configure (MetaWaylandShellSurface        *shell_surf
 
   zxdg_popup_v6_send_configure (xdg_popup->resource,
                                 x, y,
-                                configuration->width, configuration->height);
+                                configuration->width / configuration->scale,
+                                configuration->height / configuration->scale);
   meta_wayland_zxdg_surface_v6_send_configure (xdg_surface, configuration);
 }
 
diff --git a/src/wayland/meta-wayland-window-configuration.c b/src/wayland/meta-wayland-window-configuration.c
index 013f10a732..a0ee8f805c 100644
--- a/src/wayland/meta-wayland-window-configuration.c
+++ b/src/wayland/meta-wayland-window-configuration.c
@@ -29,6 +29,7 @@ meta_wayland_window_configuration_new (int                 x,
                                        int                 y,
                                        int                 width,
                                        int                 height,
+                                       int                 scale,
                                        MetaMoveResizeFlags flags,
                                        MetaGravity         gravity)
 {
@@ -46,6 +47,7 @@ meta_wayland_window_configuration_new (int                 x,
     .width = width,
     .height = height,
 
+    .scale = scale,
     .gravity = gravity,
     .flags = flags,
   };
@@ -57,7 +59,8 @@ MetaWaylandWindowConfiguration *
 meta_wayland_window_configuration_new_relative (int rel_x,
                                                 int rel_y,
                                                 int width,
-                                                int height)
+                                                int height,
+                                                int scale)
 {
   MetaWaylandWindowConfiguration *configuration;
 
@@ -72,6 +75,8 @@ meta_wayland_window_configuration_new_relative (int rel_x,
     .has_size = TRUE,
     .width = width,
     .height = height,
+
+    .scale = scale,
   };
 
   return configuration;
@@ -85,6 +90,7 @@ meta_wayland_window_configuration_new_empty (void)
   configuration = g_new0 (MetaWaylandWindowConfiguration, 1);
   *configuration = (MetaWaylandWindowConfiguration) {
     .serial = ++global_serial_counter,
+    .scale = 1,
   };
 
   return configuration;
diff --git a/src/wayland/meta-wayland-window-configuration.h b/src/wayland/meta-wayland-window-configuration.h
index 61672d5e43..b524f431fc 100644
--- a/src/wayland/meta-wayland-window-configuration.h
+++ b/src/wayland/meta-wayland-window-configuration.h
@@ -43,6 +43,7 @@ struct _MetaWaylandWindowConfiguration
   int width;
   int height;
 
+  int scale;
   MetaGravity gravity;
   MetaMoveResizeFlags flags;
 };
@@ -51,13 +52,15 @@ MetaWaylandWindowConfiguration * meta_wayland_window_configuration_new (int
                                                                         int                 y,
                                                                         int                 width,
                                                                         int                 height,
+                                                                        int                 scale,
                                                                         MetaMoveResizeFlags flags,
                                                                         MetaGravity         gravity);
 
 MetaWaylandWindowConfiguration * meta_wayland_window_configuration_new_relative (int rel_x,
                                                                                  int rel_y,
                                                                                  int width,
-                                                                                 int height);
+                                                                                 int height,
+                                                                                 int scale);
 
 MetaWaylandWindowConfiguration * meta_wayland_window_configuration_new_empty (void);
 
diff --git a/src/wayland/meta-wayland-wl-shell.c b/src/wayland/meta-wayland-wl-shell.c
index f677347990..2388afd287 100644
--- a/src/wayland/meta-wayland-wl-shell.c
+++ b/src/wayland/meta-wayland-wl-shell.c
@@ -657,7 +657,8 @@ wl_shell_surface_role_configure (MetaWaylandShellSurface        *shell_surface,
 
   wl_shell_surface_send_configure (wl_shell_surface->resource,
                                    0,
-                                   configuration->width, configuration->height);
+                                   configuration->width / configuration->scale,
+                                   configuration->height / configuration->scale);
 
   wl_shell_surface->emulated_ack_configure_serial = configuration->serial;
 }
diff --git a/src/wayland/meta-wayland-xdg-shell.c b/src/wayland/meta-wayland-xdg-shell.c
index 768b909acb..176f8a908f 100644
--- a/src/wayland/meta-wayland-xdg-shell.c
+++ b/src/wayland/meta-wayland-xdg-shell.c
@@ -700,8 +700,8 @@ meta_wayland_xdg_toplevel_send_configure (MetaWaylandXdgToplevel         *xdg_to
   fill_states (xdg_toplevel, &states);
 
   xdg_toplevel_send_configure (xdg_toplevel->resource,
-                               configuration->width,
-                               configuration->height,
+                               configuration->width / configuration->scale,
+                               configuration->height / configuration->scale,
                                &states);
   wl_array_release (&states);
 
@@ -1250,7 +1250,8 @@ meta_wayland_xdg_popup_configure (MetaWaylandShellSurface        *shell_surface,
     }
   xdg_popup_send_configure (xdg_popup->resource,
                             x, y,
-                            configuration->width, configuration->height);
+                            configuration->width / configuration->scale,
+                            configuration->height / configuration->scale);
 
   meta_wayland_xdg_surface_send_configure (xdg_surface, configuration);
 }
@@ -2046,8 +2047,10 @@ meta_wayland_xdg_positioner_to_placement (MetaWaylandXdgPositioner *xdg_position
                 }
               if (configuration->has_size)
                 {
-                  parent_rect.width = configuration->width;
-                  parent_rect.height = configuration->height;
+                  parent_rect.width =
+                    configuration->width / configuration->scale;
+                  parent_rect.height =
+                    configuration->height / configuration->scale;
                 }
             }
           else if (xdg_positioner->has_parent_size)
diff --git a/src/wayland/meta-window-wayland.c b/src/wayland/meta-window-wayland.c
index e2d2d71da5..b4329d452a 100644
--- a/src/wayland/meta-window-wayland.c
+++ b/src/wayland/meta-window-wayland.c
@@ -59,6 +59,7 @@ struct _MetaWindowWayland
   int last_sent_height;
   int last_sent_rel_x;
   int last_sent_rel_y;
+  int last_sent_geometry_scale;
   MetaGravity last_sent_gravity;
 
   gboolean has_been_shown;
@@ -192,6 +193,7 @@ surface_state_changed (MetaWindow *window)
                                            wl_window->last_sent_y,
                                            wl_window->last_sent_width,
                                            wl_window->last_sent_height,
+                                           wl_window->last_sent_geometry_scale,
                                            META_MOVE_RESIZE_STATE_CHANGED,
                                            wl_window->last_sent_gravity);
 
@@ -271,8 +273,8 @@ meta_window_wayland_move_resize_internal (MetaWindow                *window,
     }
   else
     {
-      configured_width = constrained_rect.width / geometry_scale;
-      configured_height = constrained_rect.height / geometry_scale;
+      configured_width = constrained_rect.width;
+      configured_height = constrained_rect.height;
     }
 
   /* For wayland clients, the size is completely determined by the client,
@@ -334,7 +336,8 @@ meta_window_wayland_move_resize_internal (MetaWindow                *window,
                       meta_wayland_window_configuration_new_relative (rel_x,
                                                                       rel_y,
                                                                       configured_width,
-                                                                      configured_height);
+                                                                      configured_height,
+                                                                      geometry_scale);
                     meta_window_wayland_configure (wl_window, configuration);
 
                     wl_window->last_sent_rel_x = rel_x;
@@ -386,6 +389,7 @@ meta_window_wayland_move_resize_internal (MetaWindow                *window,
                                                    configured_y,
                                                    configured_width,
                                                    configured_height,
+                                                   geometry_scale,
                                                    flags,
                                                    gravity);
           meta_window_wayland_configure (wl_window, configuration);
@@ -401,6 +405,7 @@ meta_window_wayland_move_resize_internal (MetaWindow                *window,
   wl_window->last_sent_y = configured_y;
   wl_window->last_sent_width = configured_width;
   wl_window->last_sent_height = configured_height;
+  wl_window->last_sent_geometry_scale = geometry_scale;
   wl_window->last_sent_gravity = gravity;
 
   if (can_move_now)