Adds a UI element to act as placeholder.

Content.Client/Content.Client.csproj

@@ -124,6 +124,7 @@
     <Compile Include="GameObjects\Components\Power\PowerDebugTool.cs" />
     <Compile Include="UserInterface\LobbyGui.cs" />
     <Compile Include="UserInterface\NanoStyle.cs" />
+    <Compile Include="UserInterface\Placeholder.cs" />
     <Compile Include="Utility\ResourceCacheExtensions.cs" />
     <Compile Include="GameObjects\Components\Mobs\SpeciesVisualizer2D.cs" />
   </ItemGroup>

Content.Client/UserInterface/NanoStyle.cs

@@ -20,6 +20,7 @@ namespace Content.Client.UserInterface
         {
             var resCache = IoCManager.Resolve<IResourceCache>();
             var notoSans12 = resCache.GetFont("/Nano/NotoSans/NotoSans-Regular.ttf", 12);
+            var notoSans16 = resCache.GetFont("/Nano/NotoSans/NotoSans-Regular.ttf", 16);
             var notoSansBold16 = resCache.GetFont("/Nano/NotoSans/NotoSans-Bold.ttf", 16);
             var textureCloseButton = resCache.GetTexture("/Nano/cross.svg.png");
             var windowHeaderTex = resCache.GetTexture("/Nano/window_header.png");
@@ -140,6 +141,12 @@ namespace Content.Client.UserInterface
             tooltipBox.SetPatchMargin(StyleBox.Margin.All, 2);
             tooltipBox.SetContentMarginOverride(StyleBox.Margin.Horizontal, 5);
 
+            // Placeholder
+            var placeholderTexture = resCache.GetTexture("/Nano/placeholder.png");
+            var placeholder = new StyleBoxTexture { Texture = placeholderTexture };
+            placeholder.SetPatchMargin(StyleBox.Margin.All, 24);
+            placeholder.SetExpandMargin(StyleBox.Margin.All, -5);
+
             Stylesheet = new Stylesheet(new[]
             {
                 // Default font.
@@ -376,6 +383,18 @@ namespace Content.Client.UserInterface
                         ContentMarginLeftOverride = 4
                     })
                 }),
+
+                // Placeholder
+                new StyleRule(new SelectorElement(typeof(Placeholder), null, null, null), new []
+                {
+                    new StyleProperty(PanelContainer.StylePropertyPanel, placeholder),
+                }),
+
+                new StyleRule(new SelectorElement(typeof(Label), new []{Placeholder.StyleClassPlaceholderText}, null, null), new []
+                {
+                    new StyleProperty(Label.StylePropertyFont, notoSans16),
+                    new StyleProperty(Label.StylePropertyFontColor, new Color(103, 103, 103, 128)),
+                }),
             });
         }
     }

Content.Client/UserInterface/Placeholder.cs

@@ -0,0 +1,31 @@
+using Robust.Client.Interfaces.ResourceManagement;
+using Robust.Client.UserInterface.Controls;
+
+namespace Content.Client.UserInterface
+{
+    public sealed class Placeholder : PanelContainer
+    {
+        public const string StyleClassPlaceholderText = "PlaceholderText";
+
+        private readonly Label _label;
+
+        public string PlaceholderText
+        {
+            get => _label.Text;
+            set => _label.Text = value;
+        }
+
+        public Placeholder(IResourceCache _resourceCache)
+        {
+            _label = new Label
+            {
+                SizeFlagsHorizontal = SizeFlags.Fill,
+                SizeFlagsVertical = SizeFlags.Fill,
+                Align = Label.AlignMode.Center,
+                VAlign = Label.VAlignMode.Center
+            };
+            _label.AddStyleClass(StyleClassPlaceholderText);
+            AddChild(_label);
+        }
+    }
+}