exo: Initial support for multiple displays in ARC

components/exo/wayland/server.cc

Index: components/exo/wayland/server.cc
diff --git a/components/exo/wayland/server.cc b/components/exo/wayland/server.cc
index 4386237bcd910fbc612de340bd0b24620c6d5708..326bc42234a2f092a933db3b1e12f2c6770d4b53 100644
--- a/components/exo/wayland/server.cc
+++ b/components/exo/wayland/server.cc
@@ -1983,7 +1983,7 @@ void remote_surface_ack_configure(wl_client* client,
 }
 
 void remote_surface_move(wl_client* client, wl_resource* resource) {
-  NOTIMPLEMENTED();
+  GetUserDataAs<ShellSurface>(resource)->Move();
 }
 
 const struct zcr_remote_surface_v1_interface remote_surface_implementation = {
@@ -2024,6 +2024,25 @@ const struct zcr_notification_surface_v1_interface
 
 // Implements remote shell interface and monitors workspace state needed
 // for the remote shell interface.
+//
+// This class is also responsible for conversion between server-side screen
+// coordinates and client-side virtual coordinates. This mapping enables
+// support for multiple displays when the client is limited to a single
+// display. In that case, the client uses a virtual display computed as
+// the bounding box of the physical displays, and the server translates
+// positions based on the display layout. For example, P is the client's
+// origin in virtual coordinates, and Q is the server's origin in screen
+// coordinates.
+//
+//  P        Q
+//  +-----+ /
+//  |     |/
+//  |  2  +-----------+
+//  |     |           |
+//  +-----+     1     |
+//        |           |
+//        +-----------+
+//
 class WaylandRemoteShell : public WMHelper::MaximizeModeObserver,
                            public WMHelper::ActivationObserver,
                            public display::DisplayObserver {
@@ -2057,7 +2076,19 @@ class WaylandRemoteShell : public WMHelper::MaximizeModeObserver,
 
   std::unique_ptr<ShellSurface> CreateShellSurface(Surface* surface,
                                                    int container) {
-    return display_->CreateRemoteShellSurface(surface, gfx::Point(), container);
+    gfx::Point origin = ComputeVirtualDisplayBounds().origin();
+    std::unique_ptr<ShellSurface> shell_surface =
+        display_->CreateRemoteShellSurface(surface, origin, container);
+
+    if (IsMultiDisplaySupported()) {
+      shell_surface->set_display_config_changed_callback(base::Bind(
+          [](ShellSurface* shell_surface) {
+            shell_surface->SetOrigin(ComputeVirtualDisplayBounds().origin());
+          },
+          shell_surface.get()));
+    }
+
+    return shell_surface;
   }
 
   std::unique_ptr<NotificationSurface> CreateNotificationSurface(
@@ -2067,9 +2098,20 @@ class WaylandRemoteShell : public WMHelper::MaximizeModeObserver,
   }
 
   // Overridden from display::DisplayObserver:
+  void OnDisplayAdded(const display::Display& new_display) override {
+    if (IsMultiDisplaySupported())
+      ScheduleSendDisplayMetrics(0);
+  }
+
+  void OnDisplayRemoved(const display::Display& old_display) override {
+    if (IsMultiDisplaySupported())
+      ScheduleSendDisplayMetrics(0);
+  }
+
   void OnDisplayMetricsChanged(const display::Display& display,
                                uint32_t changed_metrics) override {
-    if (display::Screen::GetScreen()->GetPrimaryDisplay().id() != display.id())
+    if (!IsMultiDisplaySupported() &&
+        display::Screen::GetScreen()->GetPrimaryDisplay().id() != display.id())
       return;
 
     // No need to update when a primary display has changed without bounds
@@ -2113,15 +2155,18 @@ class WaylandRemoteShell : public WMHelper::MaximizeModeObserver,
       return;
     needs_send_display_metrics_ = false;
 
-    const display::Screen* screen = display::Screen::GetScreen();
-    const display::Display primary_display = screen->GetPrimaryDisplay();
+    display::Display primary_display =
+        display::Screen::GetScreen()->GetPrimaryDisplay();
 
+    gfx::Size display_size = IsMultiDisplaySupported()
+                                 ? ComputeVirtualDisplayBounds().size()
+                                 : primary_display.size();
+
+    // TODO(domlaskowski): Send insets for each workspace.
     const gfx::Insets& work_area_insets = primary_display.GetWorkAreaInsets();
 
     zcr_remote_shell_v1_send_configuration_changed(
-        remote_shell_resource_,
-        primary_display.size().width(),
-        primary_display.size().height(),
+        remote_shell_resource_, display_size.width(), display_size.height(),
         OutputTransform(primary_display.rotation()),
         wl_fixed_from_double(primary_display.device_scale_factor()),
         work_area_insets.left(), work_area_insets.top(),
@@ -2162,6 +2207,14 @@ class WaylandRemoteShell : public WMHelper::MaximizeModeObserver,
     wl_client_flush(client);
   }
 
+  static gfx::Rect ComputeVirtualDisplayBounds() {
+    // Virtual screen is the bounding box of the displays in screen coordinates.
+    gfx::Rect bounds;
+    for (const auto& display : display::Screen::GetScreen()->GetAllDisplays())
+      bounds.Union(display.bounds());
+    return bounds;
+  }
+
   // The exo display instance. Not owned.
   Display* const display_;
 
@@ -2314,7 +2367,7 @@ const struct zcr_remote_shell_v1_interface remote_shell_implementation = {
     remote_shell_destroy, remote_shell_get_remote_surface,
     remote_shell_get_notification_surface};
 
-const uint32_t remote_shell_version = 2;
+const uint32_t remote_shell_version = 3;
 
 void bind_remote_shell(wl_client* client,
                        void* data,