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Added commentary about DLL boundaries. Added GetAllocatorFunctions(). Tidying up. (#3836)

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ocornut
2021-02-24 19:34:42 +01:00
parent 3f5bb5939a
commit 6f4b9c65ae
4 changed files with 47 additions and 26 deletions
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53
imgui.cpp
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@ -911,27 +911,33 @@ static void UpdateViewportsNewFrame();
// [SECTION] CONTEXT AND MEMORY ALLOCATORS
//-----------------------------------------------------------------------------
// DLL users:
// - Heaps and globals are not shared across DLL boundaries!
// - You will need to call SetCurrentContext() + SetAllocatorFunctions() for each static/DLL boundary you are calling from.
// - Same apply for hot-reloading mechanisms that are reliant on reloading DLL (note that many hot-reloading mechanism works without DLL).
// - Using Dear ImGui via a shared library is not recommended, because of function call overhead and because we don't guarantee backward nor forward ABI compatibility.
// - Confused? In a debugger: add GImGui to your watch window and notice how its value changes depending on your current location (which DLL boundary you are in).
// Current context pointer. Implicitly used by all Dear ImGui functions. Always assumed to be != NULL.
// 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.
// - ImGui::CreateContext() will automatically set this pointer if it is NULL.
// Change to a different context by calling ImGui::SetCurrentContext().
// - 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:
// - Change this variable to use thread local storage so each thread can refer to a different context, in your 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.
// - DLL users: read comments above.
#ifndef GImGui
ImGuiContext* GImGui = NULL;
#endif
// Memory Allocator functions. Use SetAllocatorFunctions() to change them.
// If you use DLL hotreloading you might need to call SetAllocatorFunctions() after reloading code from this file.
// Otherwise, you probably don't want to modify them mid-program, and if you use global/static e.g. ImVector<> instances you may need to keep them accessible during program destruction.
// - You probably don't want to modify those mid-program, and if you use global/static e.g. ImVector<> instances you may need to keep them accessible during program destruction.
// - DLL users: read comments above.
#ifndef IMGUI_DISABLE_DEFAULT_ALLOCATORS
static void* MallocWrapper(size_t size, void* user_data) { IM_UNUSED(user_data); return malloc(size); }
static void FreeWrapper(void* ptr, void* user_data) { IM_UNUSED(user_data); free(ptr); }
@ -939,10 +945,9 @@ static void FreeWrapper(void* ptr, void* user_data) { IM_UNUSED(user_d
static void* MallocWrapper(size_t size, void* user_data) { IM_UNUSED(user_data); IM_UNUSED(size); IM_ASSERT(0); return NULL; }
static void FreeWrapper(void* ptr, void* user_data) { IM_UNUSED(user_data); IM_UNUSED(ptr); IM_ASSERT(0); }
#endif
static void* (*GImAllocatorAllocFunc)(size_t size, void* user_data) = MallocWrapper;
static void (*GImAllocatorFreeFunc)(void* ptr, void* user_data) = FreeWrapper;
static void* GImAllocatorUserData = NULL;
static ImGuiMemAllocFunc* GImAllocatorAllocFunc = MallocWrapper;
static ImGuiMemFreeFunc* GImAllocatorFreeFunc = FreeWrapper;
static void* GImAllocatorUserData = NULL;
//-----------------------------------------------------------------------------
// [SECTION] USER FACING STRUCTURES (ImGuiStyle, ImGuiIO)
@ -3330,13 +3335,21 @@ void ImGui::SetCurrentContext(ImGuiContext* ctx)
#endif
}
void ImGui::SetAllocatorFunctions(void* (*alloc_func)(size_t sz, void* user_data), void (*free_func)(void* ptr, void* user_data), void* user_data)
void ImGui::SetAllocatorFunctions(ImGuiMemAllocFunc* alloc_func, ImGuiMemFreeFunc* free_func, void* user_data)
{
GImAllocatorAllocFunc = alloc_func;
GImAllocatorFreeFunc = free_func;
GImAllocatorUserData = user_data;
}
// This is provided to facilitate copying allocators from one static/DLL boundary to another (e.g. retrieve default allocator of your executable address space)
void ImGui::GetAllocatorFunctions(ImGuiMemAllocFunc** p_alloc_func, ImGuiMemFreeFunc** p_free_func, void** p_user_data)
{
*p_alloc_func = GImAllocatorAllocFunc;
*p_free_func = GImAllocatorFreeFunc;
*p_user_data = GImAllocatorUserData;
}
ImGuiContext* ImGui::CreateContext(ImFontAtlas* shared_font_atlas)
{
ImGuiContext* ctx = IM_NEW(ImGuiContext)(shared_font_atlas);