Rename thirdparty -> vendor

vendor/imgui/backends/imgui_impl_null.h

@@ -0,0 +1,34 @@
+// dear imgui: Null Platform+Renderer Backends
+// This is designed if you need to use a blind Dear Imgui context with no input and no output.
+
+// 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
+
+// Follow "Getting Started" link and check examples/ folder to learn about using backends!
+
+// Null = NullPlatform + NullRender
+IMGUI_IMPL_API bool     ImGui_ImplNull_Init();
+IMGUI_IMPL_API void     ImGui_ImplNull_Shutdown();
+IMGUI_IMPL_API void     ImGui_ImplNull_NewFrame();
+
+// Null platform only (single screen, fixed timestep, no inputs)
+IMGUI_IMPL_API bool     ImGui_ImplNullPlatform_Init();
+IMGUI_IMPL_API void     ImGui_ImplNullPlatform_Shutdown();
+IMGUI_IMPL_API void     ImGui_ImplNullPlatform_NewFrame();
+
+// Null renderer only (no output)
+IMGUI_IMPL_API bool     ImGui_ImplNullRender_Init();
+IMGUI_IMPL_API void     ImGui_ImplNullRender_Shutdown();
+IMGUI_IMPL_API void     ImGui_ImplNullRender_NewFrame();
+IMGUI_IMPL_API void     ImGui_ImplNullRender_RenderDrawData(ImDrawData* draw_data);
+
+#endif // #ifndef IMGUI_DISABLE