Backends: Made all backends sources files support global IMGUI_DISABLE. (#6601)

backends/imgui_impl_dx9.h

@@ -5,13 +5,14 @@
 //  [X] Renderer: User texture binding. Use 'LPDIRECT3DTEXTURE9' as ImTextureID. Read the FAQ about ImTextureID!
 //  [X] Renderer: Large meshes support (64k+ vertices) with 16-bit indices.
 
-// You can use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this. 
+// 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.
 // 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
 
 #pragma once
 #include "imgui.h"      // IMGUI_IMPL_API
+#ifndef IMGUI_DISABLE
 
 struct IDirect3DDevice9;
 
@@ -23,3 +24,5 @@ IMGUI_IMPL_API void     ImGui_ImplDX9_RenderDrawData(ImDrawData* draw_data);
 // Use if you want to reset your rendering device without losing Dear ImGui state.
 IMGUI_IMPL_API bool     ImGui_ImplDX9_CreateDeviceObjects();
 IMGUI_IMPL_API void     ImGui_ImplDX9_InvalidateDeviceObjects();
+
+#endif // #ifndef IMGUI_DISABLE