eis: Rebuild absolute pointers when any viewport changes

This fixes remote desktop client side resize via changing virtual
monitor stream sizes.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3241>

src/backends/meta-eis-viewport.c

@@ -20,11 +20,26 @@
 
 #include "backends/meta-eis-viewport.h"
 
+enum
+{
+  VIEWPORT_CHANGED,
+
+  N_SIGNALS
+};
+
+static guint signals[N_SIGNALS];
+
 G_DEFINE_INTERFACE (MetaEisViewport, meta_eis_viewport, G_TYPE_OBJECT)
 
 static void
 meta_eis_viewport_default_init (MetaEisViewportInterface *iface)
 {
+  signals[VIEWPORT_CHANGED] =
+    g_signal_new ("viewport-changed",
+                  G_TYPE_FROM_INTERFACE (iface),
+                  G_SIGNAL_RUN_LAST,
+                  0, NULL, NULL, NULL,
+                  G_TYPE_NONE, 0);
 }
 
 gboolean
@@ -78,3 +93,9 @@ meta_eis_viewport_transform_coordinate (MetaEisViewport *viewport,
                                                                        out_x,
                                                                        out_y);
 }
+
+void
+meta_eis_viewport_notify_changed (MetaEisViewport *viewport)
+{
+  g_signal_emit (viewport, signals[VIEWPORT_CHANGED], 0);
+}

src/backends/meta-eis-viewport.h

@@ -68,3 +68,5 @@ gboolean meta_eis_viewport_transform_coordinate (MetaEisViewport *viewport,
                                                  double           y,
                                                  double          *out_x,
                                                  double          *out_y);
+
+void meta_eis_viewport_notify_changed (MetaEisViewport *viewport);

src/backends/meta-eis.c

@@ -315,18 +315,29 @@ meta_eis_get_device_types (MetaEis *eis)
   return eis->device_types;
 }
 
+static void
+on_viewport_changed (MetaEisViewport *viewport,
+                     MetaEis         *eis)
+{
+  g_signal_emit (eis, signals[VIEWPORTS_CHANGED], 0);
+}
+
 void
 meta_eis_add_viewport (MetaEis         *eis,
                        MetaEisViewport *viewport)
 {
   eis->viewports = g_list_append (eis->viewports, viewport);
   g_signal_emit (eis, signals[VIEWPORTS_CHANGED], 0);
+
+  g_signal_connect (viewport, "viewport-changed",
+                    G_CALLBACK (on_viewport_changed), eis);
 }
 
 void
 meta_eis_remove_viewport (MetaEis         *eis,
                           MetaEisViewport *viewport)
 {
+  g_signal_handlers_disconnect_by_func (viewport, on_viewport_changed, eis);
   eis->viewports = g_list_remove (eis->viewports, viewport);
   g_signal_emit (eis, signals[VIEWPORTS_CHANGED], 0);
 }
@@ -335,6 +346,16 @@ void
 meta_eis_take_viewports (MetaEis *eis,
                          GList   *viewports)
 {
+  GList *l;
+
+  for (l = viewports; l; l = l->next)
+    {
+      MetaEisViewport *viewport = l->data;
+
+      g_signal_connect (viewport, "viewport-changed",
+                        G_CALLBACK (on_viewport_changed), eis);
+    }
+
   eis->viewports = g_list_concat (eis->viewports, viewports);
   g_signal_emit (eis, signals[VIEWPORTS_CHANGED], 0);
 }
@@ -342,6 +363,15 @@ meta_eis_take_viewports (MetaEis *eis,
 void
 meta_eis_remove_all_viewports (MetaEis *eis)
 {
+  GList *l;
+
+  for (l = eis->viewports; l; l = l->next)
+    {
+      MetaEisViewport *viewport = l->data;
+
+      g_signal_handlers_disconnect_by_func (viewport, on_viewport_changed, eis);
+    }
+
   g_clear_pointer (&eis->viewports, g_list_free);
   g_signal_emit (eis, signals[VIEWPORTS_CHANGED], 0);
 }

src/backends/meta-screen-cast-virtual-stream-src.c

@@ -22,6 +22,7 @@
 
 #include "backends/meta-crtc-mode.h"
 #include "backends/meta-cursor-tracker-private.h"
+#include "backends/meta-eis-viewport.h"
 #include "backends/meta-monitor.h"
 #include "backends/meta-output.h"
 #include "backends/meta-screen-cast-session.h"
@@ -243,10 +244,13 @@ on_monitors_changed (MetaMonitorManager             *monitor_manager,
 {
   MetaScreenCastStreamSrc *src = META_SCREEN_CAST_STREAM_SRC (virtual_src);
   MetaStage *stage = META_STAGE (stage_from_src (src));
+  MetaScreenCastStream *stream = meta_screen_cast_stream_src_get_stream (src);
 
   meta_stage_remove_watch (stage, virtual_src->watch);
   virtual_src->watch = NULL;
   add_watch (virtual_src);
+
+  meta_eis_viewport_notify_changed (META_EIS_VIEWPORT (stream));
 }
 
 static void