fix: Warn when sending empty gumps (#2563)

### Summary

Generates a console warning when users receive an empty gump. This will help prevent client side leaks.

Projects/UOContent.Tests/Tests/Gumps/TestGumps/DynamicTestGump.cs

@@ -6,6 +6,8 @@ public class DynamicTestGump : DynamicGump
 {
     private readonly string _petName;
 
+    public bool HasVisualElementsForTest => HasVisualElements;
+
     public DynamicTestGump(string petName) : base(50, 50)
     {
         _petName = petName;

Projects/UOContent.Tests/Tests/Gumps/TestGumps/EmptyTestGumps.cs

@@ -0,0 +1,40 @@
+using Server.Gumps;
+
+namespace Server.Tests.Gumps;
+
+public sealed class EmptyLegacyTestGump : Gump
+{
+    public bool HasVisualElementsForTest => HasVisualElements;
+
+    public EmptyLegacyTestGump() : base(0, 0)
+    {
+    }
+}
+
+public sealed class EmptyDynamicTestGump : DynamicGump
+{
+    public bool HasVisualElementsForTest => HasVisualElements;
+
+    public EmptyDynamicTestGump() : base(0, 0)
+    {
+    }
+
+    protected override void BuildLayout(ref DynamicGumpBuilder builder)
+    {
+        builder.AddPage();
+    }
+}
+
+public sealed class EmptyStaticTestGump : StaticGump<EmptyStaticTestGump>
+{
+    public bool HasVisualElementsForTest => HasVisualElements;
+
+    public EmptyStaticTestGump() : base(0, 0)
+    {
+    }
+
+    protected override void BuildLayout(ref StaticGumpBuilder builder)
+    {
+        builder.SetNoClose();
+    }
+}

Projects/UOContent.Tests/Tests/Gumps/TestGumps/LegacyTestGump.cs

@@ -4,6 +4,8 @@ namespace Server.Tests.Gumps;
 
 public sealed class LegacyTestGump : Gump
 {
+    public bool HasVisualElementsForTest => HasVisualElements;
+
     public LegacyTestGump(string petName) : base(50, 50)
     {
         Serial = (Serial)0x123;

Projects/UOContent.Tests/Tests/Gumps/TestGumps/StaticTestGump.cs

@@ -4,6 +4,8 @@ namespace Server.Tests.Gumps;
 
 public class StaticTestGump : StaticGump<StaticTestGump>
 {
+    public bool HasVisualElementsForTest => HasVisualElements;
+
     public StaticTestGump() : base(50, 50)
     {
         Serial = (Serial)0x123;

Projects/UOContent.Tests/Tests/Gumps/TestLayoutGumps.cs

@@ -73,6 +73,32 @@ public class TestLayoutGumps
         AssertThat.Equal(writer.Span, packet);
     }
 
+    [Fact]
+    public void TestEmptyGumpsHaveNoVisualElements()
+    {
+        Assert.False(Compile(new EmptyLegacyTestGump()).HasVisualElementsForTest);
+        Assert.False(Compile(new EmptyDynamicTestGump()).HasVisualElementsForTest);
+        Assert.False(Compile(new EmptyStaticTestGump()).HasVisualElementsForTest);
+        Assert.False(Compile(new EmptyStaticTestGump()).HasVisualElementsForTest);
+    }
+
+    [Fact]
+    public void TestVisibleGumpsHaveVisualElements()
+    {
+        Assert.True(Compile(new LegacyTestGump("Test")).HasVisualElementsForTest);
+        Assert.True(Compile(new DynamicTestGump("Test")).HasVisualElementsForTest);
+        Assert.True(Compile(new StaticTestGump()).HasVisualElementsForTest);
+        Assert.True(Compile(new StaticTestGump()).HasVisualElementsForTest);
+    }
+
+    private static T Compile<T>(T gump) where T : BaseGump
+    {
+        var buffer = GC.AllocateUninitializedArray<byte>(512);
+        var writer = new SpanWriter(buffer);
+        gump.Compile(ref writer);
+        return gump;
+    }
+
     private static void InternalTestStaticGump<T>(ReadOnlySpan<byte> expectedLayout, StaticGump<T> staticGump, string[] strings)
         where T : StaticGump<T>
     {

Projects/UOContent/Gumps/Base/BaseGump.cs

@@ -13,6 +13,7 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>. *
  *************************************************************************/
 
+using Server.Logging;
 using Server.Network;
 using System;
 using System.Buffers;
@@ -23,10 +24,12 @@ namespace Server.Gumps;
 public abstract class BaseGump
 {
     private static readonly byte[] _packetBuffer = GC.AllocateUninitializedArray<byte>(0x10000);
+    private static readonly ILogger _logger = LogFactory.GetLogger(typeof(BaseGump));
     private static Serial nextSerial = (Serial)1;
 
     public int TypeID { get; protected set; }
     public Serial Serial { get; protected set; }
+    protected bool HasVisualElements { get; set; }
 
     public abstract int Switches { get; }
     public abstract int TextEntries { get; }
@@ -56,6 +59,11 @@ public abstract class BaseGump
         var writer = new SpanWriter(_packetBuffer);
         Compile(ref writer);
 
+        if (!HasVisualElements)
+        {
+            _logger.Warning("Sending empty gump {GumpType}", GetType().FullName);
+        }
+
         ns.Send(writer.Span);
 
         writer.Dispose();

Projects/UOContent/Gumps/Base/DynamicGump.cs

@@ -47,6 +47,7 @@ public abstract class DynamicGump : BaseGump
         BuildLayout(ref gumpBuilder);
         gumpBuilder.FinalizeLayout();
 
+        HasVisualElements = gumpBuilder.HasVisualElements;
         _switches = gumpBuilder.Switches;
         _textEntries = gumpBuilder.TextEntries;
 

Projects/UOContent/Gumps/Base/DynamicGumpBuilder.cs

@@ -36,6 +36,7 @@ public ref struct DynamicGumpBuilder
 
     public int Switches => _gumpBuilder._switches;
     public int TextEntries => _gumpBuilder._textEntries;
+    internal bool HasVisualElements => _gumpBuilder._hasVisualElements;
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public DynamicGumpBuilder()

Projects/UOContent/Gumps/Base/GumpLayoutBuilder.cs

@@ -30,6 +30,7 @@ public ref struct GumpLayoutBuilder
     internal GumpFlags _flags;
     internal int _switches;
     internal int _textEntries;
+    internal bool _hasVisualElements;
 
     internal Span<byte> LayoutData => _layoutBuffer.AsSpan(0, _bytesWritten);
 
@@ -95,6 +96,7 @@ public ref struct GumpLayoutBuilder
 
     public void AddBackground(int x, int y, int width, int height, int gumpId)
     {
+        _hasVisualElements = true;
         GrowIfNeeded(9 + 9 + 45);
         WriteStart("resizepic"u8);
         WriteValue(x);
@@ -109,6 +111,7 @@ public ref struct GumpLayoutBuilder
         int x, int y, int normalId, int pressedId, int buttonId, GumpButtonType type = GumpButtonType.Reply, int param = 0
     )
     {
+        _hasVisualElements = true;
         GrowIfNeeded(11 + 6 + 54 + 2);
         WriteStart("button"u8);
         WriteValue(x);
@@ -123,6 +126,7 @@ public ref struct GumpLayoutBuilder
 
     public void AddCheckbox(int x, int y, int inactiveId, int activeId, bool selected, int switchId)
     {
+        _hasVisualElements = true;
         GrowIfNeeded(10 + 8 + 45 + 2);
         WriteStart("checkbox"u8);
         WriteValue(x);
@@ -154,6 +158,7 @@ public ref struct GumpLayoutBuilder
     public int AddHtmlPlaceholder(int x, int y, int width, int height,
         bool background = false, bool scrollbar = false)
     {
+        _hasVisualElements = true;
         GrowIfNeeded(11 + 8 + 36 + 10);
         WriteStart("htmlgump"u8);
         WriteValue(x);
@@ -172,6 +177,7 @@ public ref struct GumpLayoutBuilder
     public void AddHtml(int x, int y, int width, int height, int text,
         bool background = false, bool scrollbar = false)
     {
+        _hasVisualElements = true;
         GrowIfNeeded(11 + 8 + 45 + 4);
         WriteStart("htmlgump"u8);
         WriteValue(x);
@@ -188,6 +194,7 @@ public ref struct GumpLayoutBuilder
         int x, int y, int width, int height, int number, bool background = false, bool scrollbar = false
     )
     {
+        _hasVisualElements = true;
         GrowIfNeeded(11 + 11 + 45 + 4);
         WriteStart("xmfhtmlgump"u8);
         WriteValue(x);
@@ -204,6 +211,7 @@ public ref struct GumpLayoutBuilder
         int x, int y, int width, int height, int number, int color, bool background = false, bool scrollbar = false
     )
     {
+        _hasVisualElements = true;
         GrowIfNeeded(12 + 16 + 45 + 5 + 4);
         WriteStart("xmfhtmlgumpcolor"u8);
         WriteValue(x);
@@ -220,6 +228,7 @@ public ref struct GumpLayoutBuilder
     public void AddHtmlLocalized(int x, int y, int width, int height, int number, ReadOnlySpan<char> args, int color,
         bool background = false, bool scrollbar = false)
     {
+        _hasVisualElements = true;
         GrowIfNeeded(12 + 10 + 45 + 5 + 4 + (args.Length > 0 ? 3 + args.Length : 0));
         WriteStart("xmfhtmltok"u8);
         WriteValue(x);
@@ -254,6 +263,7 @@ public ref struct GumpLayoutBuilder
 
     public void AddImage(int x, int y, int gumpId, int hue = 0, ReadOnlySpan<char> cls = default)
     {
+        _hasVisualElements = true;
         GrowIfNeeded(7 + 7 + 36 + (hue != 0 ? 14 : 0) + (cls.Length > 0 ? 7 + cls.Length : 0));
         WriteStart("gumppic"u8);
         WriteValue(x);
@@ -294,6 +304,7 @@ public ref struct GumpLayoutBuilder
     public void AddImageTiledButton(int x, int y, int normalId, int pressedId, int buttonId, GumpButtonType type, int param,
         int itemId, int hue, int width, int height, int localizedTooltip = -1)
     {
+        _hasVisualElements = true;
         GrowIfNeeded(15 + 13 + 90 + 2);
         WriteStart("buttontileart"u8);
         WriteValue(x);
@@ -319,6 +330,7 @@ public ref struct GumpLayoutBuilder
 
     public void AddImageTiled(int x, int y, int width, int height, int gumpId)
     {
+        _hasVisualElements = true;
         GrowIfNeeded(9 + 12 + 45);
         WriteStart("gumppictiled"u8);
         WriteValue(x);
@@ -331,6 +343,7 @@ public ref struct GumpLayoutBuilder
 
     public void AddItem(int x, int y, int itemId, int hue = 0)
     {
+        _hasVisualElements = true;
         GrowIfNeeded(7 + 36 + (hue != 0 ? 20 : 7));
         WriteStart(hue == 0 ? "tilepic"u8 : "tilepichue"u8);
         WriteValue(x);
@@ -355,6 +368,7 @@ public ref struct GumpLayoutBuilder
 
     public int AddLabelPlaceholder(int x, int y, int hue)
     {
+        _hasVisualElements = true;
         GrowIfNeeded(8 + 4 + 27 + 6);
         WriteStart("text"u8);
         WriteValue(x);
@@ -368,6 +382,7 @@ public ref struct GumpLayoutBuilder
 
     public void AddLabel(int x, int y, int hue, int text)
     {
+        _hasVisualElements = true;
         GrowIfNeeded(8 + 4 + 36 + 6);
         WriteStart("text"u8);
         WriteValue(x);
@@ -379,6 +394,7 @@ public ref struct GumpLayoutBuilder
 
     public int AddLabelCroppedPlaceholder(int x, int y, int width, int height, int hue)
     {
+        _hasVisualElements = true;
         GrowIfNeeded(10 + 11 + 45 + 6);
         WriteStart("croppedtext"u8);
         WriteValue(x);
@@ -394,6 +410,7 @@ public ref struct GumpLayoutBuilder
 
     public void AddLabelCropped(int x, int y, int width, int height, int hue, int text)
     {
+        _hasVisualElements = true;
         GrowIfNeeded(10 + 11 + 54 + 6);
         WriteStart("croppedtext"u8);
         WriteValue(x);
@@ -430,6 +447,7 @@ public ref struct GumpLayoutBuilder
 
     public void AddRadio(int x, int y, int inactiveId, int activeId, bool selected, int switchId)
     {
+        _hasVisualElements = true;
         GrowIfNeeded(10 + 5 + 45 + 2);
         WriteStart("radio"u8);
         WriteValue(x);
@@ -445,6 +463,7 @@ public ref struct GumpLayoutBuilder
 
     public void AddSpriteImage(int x, int y, int gumpId, int width, int height, int sx, int sy)
     {
+        _hasVisualElements = true;
         GrowIfNeeded(11 + 8 + 63);
         WriteStart("picinpic"u8);
         WriteValue(x);
@@ -461,6 +480,7 @@ public ref struct GumpLayoutBuilder
         int x, int y, int width, int height, int hue, int entryId
     )
     {
+        _hasVisualElements = true;
         GrowIfNeeded(11 + 9 + 54 + 6);
         WriteStart("textentry"u8);
         WriteValue(x);
@@ -481,6 +501,7 @@ public ref struct GumpLayoutBuilder
         int x, int y, int width, int height, int hue, int entryId, int initialText
     )
     {
+        _hasVisualElements = true;
         GrowIfNeeded(11 + 9 + 63 + 6);
         WriteStart("textentry"u8);
         WriteValue(x);
@@ -499,6 +520,7 @@ public ref struct GumpLayoutBuilder
         int x, int y, int width, int height, int hue, int entryId, int size = 0
     )
     {
+        _hasVisualElements = true;
         GrowIfNeeded(12 + 16 + 63 + 6);
         WriteStart("textentrylimited"u8);
         WriteValue(x);
@@ -520,6 +542,7 @@ public ref struct GumpLayoutBuilder
         int x, int y, int width, int height, int hue, int entryId, int initialText, int size = 0
     )
     {
+        _hasVisualElements = true;
         GrowIfNeeded(12 + 16 + 72);
         WriteStart("textentrylimited"u8);
         WriteValue(x);

Projects/UOContent/Gumps/Base/Legacy/Gump.cs

@@ -249,6 +249,7 @@ public class Gump : BaseGump
     {
         _textEntries = 0;
         _switches = 0;
+        HasVisualElements = false;
 
         var layoutWriter = new SpanWriter(_layoutBuffer);
 
@@ -274,6 +275,7 @@ public class Gump : BaseGump
 
         foreach (var entry in Entries)
         {
+            HasVisualElements |= IsVisualEntry(entry);
             entry.AppendTo(ref layoutWriter, _stringsList, ref _textEntries, ref _switches);
         }
 
@@ -311,6 +313,9 @@ public class Gump : BaseGump
         }
     }
 
+    private static bool IsVisualEntry(GumpEntry entry) =>
+        entry is not (GumpAlphaRegion or GumpECHandleInput or GumpGroup or GumpItemProperty or GumpMasterGump or GumpPage or GumpTooltip);
+
     protected void Reset()
     {
         _switches = 0;

Projects/UOContent/Gumps/Base/StaticGump.cs

@@ -30,6 +30,7 @@ public abstract class StaticGump<TSelf> : BaseGump where TSelf : StaticGump<TSel
     private static byte[] _compressedStringsData;
 
     private static bool _hasDynamicStrings;
+    private static bool _cachedHasVisualElements;
     private static int _staticStringsCount;
     private static byte[] _staticStrings;
 
@@ -72,6 +73,7 @@ public abstract class StaticGump<TSelf> : BaseGump where TSelf : StaticGump<TSel
 
         if (Cached && _compressedLayoutData != null)
         {
+            HasVisualElements = _cachedHasVisualElements;
             writer.Write(_compressedLayoutData);
 
             if (_compressedStringsData != null)
@@ -116,6 +118,7 @@ public abstract class StaticGump<TSelf> : BaseGump where TSelf : StaticGump<TSel
             BuildLayout(ref gumpBuilder);
             gumpBuilder.FinalizeLayout();
 
+            HasVisualElements = _cachedHasVisualElements = gumpBuilder.HasVisualElements;
             _switches = gumpBuilder.Switches;
             _textEntries = gumpBuilder.TextEntries;
             _staticStringsCount = gumpBuilder._stringsCount;

Projects/UOContent/Gumps/Base/StaticGumpBuilder.cs

@@ -43,6 +43,7 @@ public ref struct StaticGumpBuilder
 
     public int Switches => _gumpBuilder._switches;
     public int TextEntries => _gumpBuilder._textEntries;
+    internal bool HasVisualElements => _gumpBuilder._hasVisualElements;
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public StaticGumpBuilder()