Better font wrappers, some style/naming revision, new wrappers

* Font -> NativeFont. Font is now a wrapper class for the NativeFont
  struct.
* FontAtlasWrapped -> FontAtlas, and FontAtlas -> NativeFontAtlas, in line
  with other native struct wrappers.
* [BREAKING CHANGE] Removed ImGui.LoadDefaultFont(). It is now available on FontAtlas along
  with other Font loading methods. This makes more sense w.r.t. the actual
  native interface.
  * Modified the SampleProgram to account for the above.
* New wrapper: ImGui.SetKeyboardFocusHere([int offset])

src/ImGui.NET.SampleProgram/SampleWindow.cs

@@ -47,7 +47,7 @@ namespace ImGuiNET
             _nativeWindow.KeyUp += OnKeyUp;
             _nativeWindow.KeyPress += OnKeyPress;
 
-            ImGui.LoadDefaultFont();
+            ImGui.GetIO().FontAtlas.AddDefaultFont();
 
             SetOpenTKKeyMappings();
 

src/ImGui.NET/Font.cs

@@ -4,12 +4,22 @@ using System.Numerics;
 
 namespace ImGuiNET
 {
+    public unsafe class Font
+    {
+        public Font(NativeFont* nativePtr)
+        {
+            NativeFont = nativePtr;
+        }
+
+        public NativeFont* NativeFont { get; }
+    }
+
     /// <summary>
     /// Font runtime data and rendering.
     /// ImFontAtlas automatically loads a default embedded font for you when you call GetTexDataAsAlpha8() or GetTexDataAsRGBA32().
     /// </summary>
     [StructLayout(LayoutKind.Sequential)]
-    public unsafe struct Font
+    public unsafe struct NativeFont
     {
         // Members: Settings
 

src/ImGui.NET/FontAtlas.cs

@@ -13,7 +13,7 @@ namespace ImGuiNET
     //  4. Call SetTexID(my_tex_id); and pass the pointer/identifier to your texture. This value will be passed back to you during rendering to identify the texture.
     //  5. Call ClearTexData() to free textures memory on the heap.
     [StructLayout(LayoutKind.Sequential)]
-    public unsafe struct FontAtlas
+    public unsafe struct NativeFontAtlas
     {
         // Members
         // (Access texture data via GetTexData*() calls which will setup a default font for you.)

src/ImGui.NET/IO.cs

@@ -14,7 +14,7 @@ namespace ImGuiNET
             MouseDown = new MouseDownStates(nativePtr);
             KeyMap = new KeyMap(_nativePtr);
             KeysDown = new KeyDownStates(_nativePtr);
-            FontAtlas = new FontAtlasWrapped(_nativePtr->FontAtlas);
+            FontAtlas = new FontAtlas(_nativePtr->FontAtlas);
         }
 
         public NativeIO* GetNativePointer() => _nativePtr;
@@ -86,7 +86,7 @@ namespace ImGuiNET
         /// </summary>
         public KeyDownStates KeysDown { get; }
 
-        public FontAtlasWrapped FontAtlas { get; }
+        public FontAtlas FontAtlas { get; }
 
         public bool FontAllowUserScaling
         {
@@ -210,11 +210,11 @@ namespace ImGuiNET
         }
     }
 
-    public unsafe class FontAtlasWrapped
+    public unsafe class FontAtlas
     {
-        private readonly FontAtlas* _atlasPtr;
+        private readonly NativeFontAtlas* _atlasPtr;
 
-        public FontAtlasWrapped(FontAtlas* atlasPtr)
+        public FontAtlas(NativeFontAtlas* atlasPtr)
         {
             _atlasPtr = atlasPtr;
         }
@@ -253,6 +253,24 @@ namespace ImGuiNET
         {
             ImGuiNative.ImFontAtlas_ClearTexData(_atlasPtr);
         }
+
+        public Font AddDefaultFont()
+        {
+            NativeFont* nativeFontPtr = ImGuiNative.ImFontAtlas_AddFontDefault(_atlasPtr);
+            return new Font(nativeFontPtr);
+        }
+
+        public Font AddFontFromFileTTF(string fileName, float pixelSize)
+        {
+            NativeFont* nativeFontPtr = ImGuiNative.ImFontAtlas_AddFontFromFileTTF(_atlasPtr, fileName, pixelSize, IntPtr.Zero, null);
+            return new Font(nativeFontPtr);
+        }
+
+        public Font AddFontFromMemoryTTF(IntPtr ttfData, int ttfDataSize, float pixelSize)
+        {
+            NativeFont* nativeFontPtr = ImGuiNative.ImFontAtlas_AddFontFromMemoryTTF(_atlasPtr, ttfData.ToPointer(), ttfDataSize, pixelSize, IntPtr.Zero, null);
+            return new Font(nativeFontPtr);
+        }
     }
 
     public unsafe struct FontTextureData

src/ImGui.NET/ImGui.cs

@@ -32,12 +32,6 @@ namespace ImGuiNET
             return s_style;
         }
 
-        public static unsafe void LoadDefaultFont()
-        {
-            NativeIO* ioPtr = ImGuiNative.igGetIO();
-            ImGuiNative.ImFontAtlas_AddFontDefault(ioPtr->FontAtlas);
-        }
-
         public static void PushID(string id)
         {
             ImGuiNative.igPushIdStr(id);
@@ -997,5 +991,25 @@ namespace ImGuiNET
         {
             ImGuiNative.igSetScrollHere(centerYRatio);
         }
+
+        public static unsafe void PushFont(Font font)
+        {
+            ImGuiNative.igPushFont(font.NativeFont);
+        }
+
+        public static void PopFont()
+        {
+            ImGuiNative.igPopFont();
+        }
+
+        public static void SetKeyboardFocusHere()
+        {
+            ImGuiNative.igSetKeyboardFocusHere(0);
+        }
+
+        public static void SetKeyboardFocusHere(int offset)
+        {
+            ImGuiNative.igSetKeyboardFocusHere(offset);
+        }
     }
 }

src/ImGui.NET/ImGuiNative.cs

@@ -71,7 +71,7 @@ namespace ImGuiNET
         [DllImport(cimguiLib)]
         public static extern DrawList* igGetWindowDrawList();
         [DllImport(cimguiLib)]
-        public static extern Font* igGetWindowFont();
+        public static extern NativeFont* igGetWindowFont();
         [DllImport(cimguiLib)]
         public static extern float igGetWindowFontSize();
         [DllImport(cimguiLib)]
@@ -147,7 +147,7 @@ namespace ImGuiNET
 
         // Parameters stacks (shared)
         [DllImport(cimguiLib)]
-        public static extern void igPushFont(Font* font);
+        public static extern void igPushFont(NativeFont* font);
         [DllImport(cimguiLib)]
         public static extern void igPopFont();
         [DllImport(cimguiLib)]
@@ -645,6 +645,12 @@ namespace ImGuiNET
         public static extern float igGetTime();
         [DllImport(cimguiLib)]
         public static extern int igGetFrameCount();
+
+        internal static void igPushFont(object nativeFont)
+        {
+            throw new NotImplementedException();
+        }
+
         [DllImport(cimguiLib)]
         public static extern string igGetStyleColName(ColorTarget idx);
         [DllImport(cimguiLib)]
@@ -741,34 +747,34 @@ namespace ImGuiNET
 
 
         [DllImport(cimguiLib)]
-        public static extern void ImFontAtlas_GetTexDataAsRGBA32(FontAtlas* atlas, byte** out_pixels, int* out_width, int* out_height, int* out_bytes_per_pixel);
+        public static extern void ImFontAtlas_GetTexDataAsRGBA32(NativeFontAtlas* atlas, byte** out_pixels, int* out_width, int* out_height, int* out_bytes_per_pixel);
 
         [DllImport(cimguiLib)]
-        public static extern void ImFontAtlas_GetTexDataAsAlpha8(FontAtlas* atlas, byte** out_pixels, int* out_width, int* out_height, int* out_bytes_per_pixel);
+        public static extern void ImFontAtlas_GetTexDataAsAlpha8(NativeFontAtlas* atlas, byte** out_pixels, int* out_width, int* out_height, int* out_bytes_per_pixel);
 
         [DllImport(cimguiLib)]
-        public static extern void ImFontAtlas_SetTexID(FontAtlas* atlas, void* tex);
+        public static extern void ImFontAtlas_SetTexID(NativeFontAtlas* atlas, void* tex);
 
         [DllImport(cimguiLib)]
-        public static extern Font* ImFontAtlas_AddFont(FontAtlas* atlas, ref FontConfig font_cfg);
+        public static extern NativeFont* ImFontAtlas_AddFont(NativeFontAtlas* atlas, ref FontConfig font_cfg);
 
         [DllImport(cimguiLib)]
-        public static extern Font* ImFontAtlas_AddFontDefault(FontAtlas* atlas, IntPtr font_cfg);
+        public static extern NativeFont* ImFontAtlas_AddFontDefault(NativeFontAtlas* atlas, IntPtr font_cfg);
-        public static Font* ImFontAtlas_AddFontDefault(FontAtlas* atlas) { return ImFontAtlas_AddFontDefault(atlas, IntPtr.Zero); }
+        public static NativeFont* ImFontAtlas_AddFontDefault(NativeFontAtlas* atlas) { return ImFontAtlas_AddFontDefault(atlas, IntPtr.Zero); }
 
         [DllImport(cimguiLib)]
-        public static extern Font* ImFontAtlas_AddFontFromFileTTF(FontAtlas* atlas, string filename, float size_pixels, IntPtr font_cfg, char* glyph_ranges);
+        public static extern NativeFont* ImFontAtlas_AddFontFromFileTTF(NativeFontAtlas* atlas, string filename, float size_pixels, IntPtr font_cfg, char* glyph_ranges);
         [DllImport(cimguiLib)]
-        public static extern Font* ImFontAtlas_AddFontFromMemoryTTF(FontAtlas* atlas, void* ttf_data, int ttf_size, float size_pixels, IntPtr font_cfg, char* glyph_ranges);
+        public static extern NativeFont* ImFontAtlas_AddFontFromMemoryTTF(NativeFontAtlas* atlas, void* ttf_data, int ttf_size, float size_pixels, IntPtr font_cfg, char* glyph_ranges);
         [DllImport(cimguiLib)]
-        public static extern Font* ImFontAtlas_AddFontFromMemoryCompressedTTF(FontAtlas* atlas, void* compressed_ttf_data, int compressed_ttf_size, float size_pixels, FontConfig* font_cfg, char* glyph_ranges);
+        public static extern NativeFont* ImFontAtlas_AddFontFromMemoryCompressedTTF(NativeFontAtlas* atlas, void* compressed_ttf_data, int compressed_ttf_size, float size_pixels, FontConfig* font_cfg, char* glyph_ranges);
         [DllImport(cimguiLib)]
-        public static extern Font* ImFontAtlas_AddFontFromMemoryCompressedBase85TTF(FontAtlas* atlas, string compressed_ttf_data_base85, float size_pixels, FontConfig* font_cfg, char* glyph_ranges);
+        public static extern NativeFont* ImFontAtlas_AddFontFromMemoryCompressedBase85TTF(NativeFontAtlas* atlas, string compressed_ttf_data_base85, float size_pixels, FontConfig* font_cfg, char* glyph_ranges);
 
         [DllImport(cimguiLib)]
-        public static extern void ImFontAtlas_ClearTexData(FontAtlas* atlas);
+        public static extern void ImFontAtlas_ClearTexData(NativeFontAtlas* atlas);
         [DllImport(cimguiLib)]
-        public static extern void ImFontAtlas_Clear(FontAtlas* atlas);
+        public static extern void ImFontAtlas_Clear(NativeFontAtlas* atlas);
 
 
         [DllImport(cimguiLib)]

src/ImGui.NET/NativeIO.cs

@@ -77,7 +77,7 @@ namespace ImGuiNET
         /// Load and assemble one or more fonts into a single tightly packed texture. Output to Fonts array.
         /// Default value: [auto]
         /// </summary>
-        public FontAtlas* FontAtlas;
+        public NativeFontAtlas* FontAtlas;
         /// <summary>
         /// Global scale all fonts.
         /// Default value: 1.0f.