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Comments about DLL boundaries and using TLS variables for GImGui. (#2292)

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omar 2019-01-18 23:02:58 +01:00
parent 92d29531fa
commit fcd61e0c59
1 changed files with 13 additions and 5 deletions
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18
imgui.cpp
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@ -1038,11 +1038,19 @@ static void UpdateManualResize(ImGuiWindow* window, const ImVec2& si
//-----------------------------------------------------------------------------
// Current context pointer. Implicitly used by all Dear ImGui functions. Always assumed to be != NULL.
// CreateContext() will automatically set this pointer if it is NULL. Change to a different context by calling ImGui::SetCurrentContext().
// If you use DLL hotreloading you might need to call SetCurrentContext() after reloading code from this file.
// ImGui functions are not thread-safe because of this pointer. If you want thread-safety to allow N threads to access N different contexts, you can:
// - Change this variable to use thread local storage. You may #define GImGui in imconfig.h for that purpose. Future development aim to make this context pointer explicit to all calls. Also read https://github.com/ocornut/imgui/issues/586
// - Having multiple instances of the ImGui code compiled inside different namespace (easiest/safest, if you have a finite number of contexts)
// ImGui::CreateContext() will automatically set this pointer if it is NULL. Change to a different context by calling ImGui::SetCurrentContext().
// 1) Important: globals are not shared across DLL boundaries! If you use DLLs or any form of hot-reloading: you will need to call
// SetCurrentContext() (with the pointer you got from CreateContext) from each unique static/DLL boundary, and after each hot-reloading.
// In your debugger, add GImGui to your watch window and notice how its value changes depending on which location you are currently stepping into.
// 2) Important: Dear ImGui functions are not thread-safe because of this pointer.
// If you want thread-safety to allow N threads to access N different contexts, you can:
// - Change this variable to use thread local storage so each thread can refer to a different context, in imconfig.h:
// struct ImGuiContext;
// extern thread_local ImGuiContext* MyImGuiTLS;
// #define GImGui MyImGuiTLS
// And then define MyImGuiTLS in one of your cpp file. Note that thread_local is a C++11 keyword, earlier C++ uses compiler-specific keyword.
// - Future development aim to make this context pointer explicit to all calls. Also read https://github.com/ocornut/imgui/issues/586
// - If you need a finite number of contexts, you may compile and use multiple instances of the ImGui code from different namespace.
#ifndef GImGui
ImGuiContext* GImGui = NULL;
#endif