v2: Update example plugin imgui backends to match current imgui version

Copied imgui_impl_dx11/dx12/win32 from dependencies/imgui/backends/.
Added ImGui_ImplWin32_WndProcHandler forward declaration in Plugin.cpp
(required by newer imgui which wraps the declaration in #if 0).

Author: praydog

examples/example_plugin/Plugin.cpp

@@ -12,6 +12,9 @@
 #include "imgui/imgui_impl_dx12.h"
 #include "imgui/imgui_impl_win32.h"
 
+// Forward declaration required by newer imgui backends
+extern IMGUI_IMPL_API LRESULT ImGui_ImplWin32_WndProcHandler(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam);
+
 #include "rendering/d3d11.hpp"
 #include "rendering/d3d12.hpp"
 

examples/example_plugin/imgui/imgui_impl_dx11.cpp

@@ -2,24 +2,50 @@
 // This needs to be used along with a Platform Backend (e.g. Win32)
 
 // Implemented features:
-//  [X] Renderer: User texture binding. Use 'ID3D11ShaderResourceView*' as ImTextureID. Read the FAQ about ImTextureID!
-//  [X] Renderer: Support for large meshes (64k+ vertices) with 16-bit indices.
+//  [X] Renderer: User texture binding. Use 'ID3D11ShaderResourceView*' as texture identifier. Read the FAQ about ImTextureID/ImTextureRef!
+//  [X] Renderer: Large meshes support (64k+ vertices) even with 16-bit indices (ImGuiBackendFlags_RendererHasVtxOffset).
+//  [X] Renderer: Texture updates support for dynamic font atlas (ImGuiBackendFlags_RendererHasTextures).
+//  [X] Renderer: Expose selected render state for draw callbacks to use. Access in '(ImGui_ImplXXXX_RenderState*)GetPlatformIO().Renderer_RenderState'.
 
-// You can copy and use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this.
-// If you are new to Dear ImGui, read documentation from the docs/ folder + read the top of imgui.cpp.
-// Read online: https://github.com/ocornut/imgui/tree/master/docs
+// You can use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this.
+// Prefer including the entire imgui/ repository into your project (either as a copy or as a submodule), and only build the backends you need.
+// Learn about Dear ImGui:
+// - FAQ                  https://dearimgui.com/faq
+// - Getting Started      https://dearimgui.com/getting-started
+// - Documentation        https://dearimgui.com/docs (same as your local docs/ folder).
+// - Introduction, links and more at the top of imgui.cpp
 
 #pragma once
 #include "imgui.h"      // IMGUI_IMPL_API
+#ifndef IMGUI_DISABLE
 
 struct ID3D11Device;
 struct ID3D11DeviceContext;
+struct ID3D11SamplerState;
+struct ID3D11Buffer;
 
+// Follow "Getting Started" link and check examples/ folder to learn about using backends!
 IMGUI_IMPL_API bool     ImGui_ImplDX11_Init(ID3D11Device* device, ID3D11DeviceContext* device_context);
 IMGUI_IMPL_API void     ImGui_ImplDX11_Shutdown();
 IMGUI_IMPL_API void     ImGui_ImplDX11_NewFrame();
 IMGUI_IMPL_API void     ImGui_ImplDX11_RenderDrawData(ImDrawData* draw_data);
 
 // Use if you want to reset your rendering device without losing Dear ImGui state.
+IMGUI_IMPL_API bool     ImGui_ImplDX11_CreateDeviceObjects();
 IMGUI_IMPL_API void     ImGui_ImplDX11_InvalidateDeviceObjects();
-IMGUI_IMPL_API bool     ImGui_ImplDX11_CreateDeviceObjects();
+
+// (Advanced) Use e.g. if you need to precisely control the timing of texture updates (e.g. for staged rendering), by setting ImDrawData::Textures = NULL to handle this manually.
+IMGUI_IMPL_API void     ImGui_ImplDX11_UpdateTexture(ImTextureData* tex);
+
+// [BETA] Selected render state data shared with callbacks.
+// This is temporarily stored in GetPlatformIO().Renderer_RenderState during the ImGui_ImplDX11_RenderDrawData() call.
+// (Please open an issue if you feel you need access to more data)
+struct ImGui_ImplDX11_RenderState
+{
+    ID3D11Device*           Device;
+    ID3D11DeviceContext*    DeviceContext;
+    ID3D11SamplerState*     SamplerDefault;
+    ID3D11Buffer*           VertexConstantBuffer;
+};
+
+#endif // #ifndef IMGUI_DISABLE