Cherry-pick over native functions for docking / multi-viewport support.

Author: mellinoe

src/ImGui.NET/Delegates.cs

@@ -0,0 +1,17 @@
+using System;
+using System.Numerics;
+
+namespace ImGuiNET
+{
+    public delegate void Platform_CreateWindow(ImGuiViewportPtr vp);                    // Create a new platform window for the given viewport
+    public delegate void Platform_DestroyWindow(ImGuiViewportPtr vp);
+    public delegate void Platform_ShowWindow(ImGuiViewportPtr vp);                      // Newly created windows are initially hidden so SetWindowPos/Size/Title can be called on them first
+    public delegate void Platform_SetWindowPos(ImGuiViewportPtr vp, Vector2 pos);
+    public unsafe delegate void Platform_GetWindowPos(ImGuiViewportPtr vp, Vector2* outPos);
+    public delegate void Platform_SetWindowSize(ImGuiViewportPtr vp, Vector2 size);
+    public unsafe delegate void Platform_GetWindowSize(ImGuiViewportPtr vp, Vector2* outSize);
+    public delegate void Platform_SetWindowFocus(ImGuiViewportPtr vp);                  // Move window to front and set input focus
+    public delegate byte Platform_GetWindowFocus(ImGuiViewportPtr vp);
+    public delegate byte Platform_GetWindowMinimized(ImGuiViewportPtr vp);
+    public delegate void Platform_SetWindowTitle(ImGuiViewportPtr vp, IntPtr title);
+}

src/ImGui.NET/ImGuiNative.Manual.cs

@@ -0,0 +1,13 @@
+using System;
+using System.Runtime.InteropServices;
+
+namespace ImGuiNET
+{
+    public static unsafe partial class ImGuiNative
+    {
+        [DllImport("cimgui", CallingConvention = CallingConvention.Cdecl)]
+        public static extern void ImGuiPlatformIO_Set_Platform_GetWindowPos(ImGuiPlatformIO* platform_io, IntPtr funcPtr);
+        [DllImport("cimgui", CallingConvention = CallingConvention.Cdecl)]
+        public static extern void ImGuiPlatformIO_Set_Platform_GetWindowSize(ImGuiPlatformIO* platform_io, IntPtr funcPtr);
+    }
+}

src/ImGui.NET/ImVector.cs

@@ -9,6 +9,13 @@ public unsafe struct ImVector
         public readonly int Capacity;
         public readonly IntPtr Data;
 
+        public ImVector(int size, int capacity, IntPtr data)
+        {
+            Size = size;
+            Capacity = capacity;
+            Data = data;
+        }
+
         public ref T Ref<T>(int index)
         {
             return ref Unsafe.AsRef<T>((byte*)Data + index * Unsafe.SizeOf<T>());