Use StartupInputEx instead of StartupInput to ensure that we're initi…

…alizing GDI+ v2 consistently.

src/libraries/System.Drawing.Common/src/System/Drawing/Gdiplus.cs

@@ -26,11 +26,9 @@ static Gdip()
 
                 PlatformInitialize();
 
-                StartupInput input = StartupInput.GetDefault();
-
                 // GDI+ ref counts multiple calls to Startup in the same process, so calls from multiple
                 // domains are ok, just make sure to pair each w/GdiplusShutdown
-                int status = GdiplusStartup(out s_initToken, ref input, out _);
+                int status = GdiplusStartup(out s_initToken, StartupInputEx.GetDefault(), out _);
                 CheckStatus(status);
             }
 

src/libraries/System.Drawing.Common/src/System/Drawing/GdiplusNative.Unix.cs

@@ -70,7 +70,7 @@ private static void PlatformInitialize()
 
             // Imported functions
             [GeneratedDllImport(LibraryName)]
-            internal static partial int GdiplusStartup(out IntPtr token, ref StartupInput input, out StartupOutput output);
+            internal static partial int GdiplusStartup(out IntPtr token, in StartupInputEx input, out StartupOutput output);
 
             [GeneratedDllImport(LibraryName)]
             internal static partial void GdiplusShutdown(ref ulong token);

src/libraries/System.Drawing.Common/src/System/Drawing/GdiplusNative.Windows.cs

@@ -23,7 +23,7 @@ private static void PlatformInitialize()
 
             // Imported functions
             [GeneratedDllImport(LibraryName)]
-            private static partial int GdiplusStartup(out IntPtr token, ref StartupInput input, out StartupOutput output);
+            private static partial int GdiplusStartup(out IntPtr token, in StartupInputEx input, out StartupOutput output);
 
             [GeneratedDllImport(LibraryName)]
             internal static partial int GdipCreatePath(int brushMode, out IntPtr path);

src/libraries/System.Drawing.Common/src/System/Drawing/GdiplusNative.cs

@@ -3452,9 +3452,9 @@ internal static partial int GdipGetEncoderParameterList(
         }
 
         [StructLayout(LayoutKind.Sequential)]
-        internal struct StartupInput
+        internal struct StartupInputEx
         {
-            public int GdiplusVersion;             // Must be 1
+            public int GdiplusVersion;             // Must be 1 or 2
 
             public IntPtr DebugEventCallback;
 
@@ -3463,17 +3463,19 @@ internal struct StartupInput
 
             public Interop.BOOL SuppressExternalCodecs;       // FALSE unless you want GDI+ only to use
                                                       // its internal image codecs.
+            public int StartupParameters;
 
-            public static StartupInput GetDefault()
+            public static StartupInputEx GetDefault()
             {
                 OperatingSystem os = Environment.OSVersion;
-                StartupInput result = default;
+                StartupInputEx result = default;
 
                 // In Windows 7 GDI+1.1 story is different as there are different binaries per GDI+ version.
                 bool isWindows7 = os.Platform == PlatformID.Win32NT && os.Version.Major == 6 && os.Version.Minor == 1;
                 result.GdiplusVersion = isWindows7 ? 1 : 2;
                 result.SuppressBackgroundThread = Interop.BOOL.FALSE;
                 result.SuppressExternalCodecs = Interop.BOOL.FALSE;
+                result.StartupParameters = 0;
                 return result;
             }
         }