From f3f2578e8f9d89742635f286728ec6998b8e3559 Mon Sep 17 00:00:00 2001
From: Sammy Fatnassi <sammyfreg@gmail.com>
Date: Tue, 26 Jan 2021 15:14:56 +0100
Subject: [PATCH] Internals: Added context hook removal support (#3580, #3626,
 #3753)

---
 imgui.cpp        | 22 ++++++++++++++++++++--
 imgui_internal.h |  7 +++++--
 2 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/imgui.cpp b/imgui.cpp
index 78fc2fcf..8e64e341 100644
--- a/imgui.cpp
+++ b/imgui.cpp
@@ -3346,11 +3346,23 @@ void ImGui::DestroyContext(ImGuiContext* ctx)
 }
 
 // No specific ordering/dependency support, will see as needed
-void ImGui::AddContextHook(ImGuiContext* ctx, const ImGuiContextHook* hook)
+ImGuiID ImGui::AddContextHook(ImGuiContext* ctx, const ImGuiContextHook* hook)
 {
     ImGuiContext& g = *ctx;
-    IM_ASSERT(hook->Callback != NULL);
+    IM_ASSERT(hook->Callback != NULL && hook->HookId == 0 && hook->Type != ImGuiContextHookType_PendingRemoval_);
     g.Hooks.push_back(*hook);
+    g.Hooks.back().HookId = ++g.HookIdNext;
+    return g.HookIdNext;
+}
+
+// Deferred removal, avoiding issue with changing vector while iterating it
+void ImGui::RemoveContextHook(ImGuiContext* ctx, ImGuiID hook_id)
+{
+    ImGuiContext& g = *ctx;
+    IM_ASSERT(hook_id != 0);
+    for (int n = 0; n < g.Hooks.Size; n++)
+        if (g.Hooks[n].HookId == hook_id)
+            g.Hooks[n].Type = ImGuiContextHookType_PendingRemoval_;
 }
 
 // Call context hooks (used by e.g. test engine)
@@ -3780,6 +3792,12 @@ void ImGui::NewFrame()
 {
     IM_ASSERT(GImGui != NULL && "No current context. Did you call ImGui::CreateContext() and ImGui::SetCurrentContext() ?");
     ImGuiContext& g = *GImGui;
+    
+    // Remove pending delete hooks before frame start.
+    // This deferred removal avoid issues of removal while iterating the hook vector
+    for (int n = g.Hooks.Size - 1; n >= 0; n--)
+        if (g.Hooks[n].Type == ImGuiContextHookType_PendingRemoval_)
+            g.Hooks.erase(&g.Hooks[n]);
 
     CallContextHooks(&g, ImGuiContextHookType_NewFramePre);
 
diff --git a/imgui_internal.h b/imgui_internal.h
index 7e48c1c6..15c10f5e 100644
--- a/imgui_internal.h
+++ b/imgui_internal.h
@@ -1223,10 +1223,11 @@ struct IMGUI_API ImGuiStackSizes
 //-----------------------------------------------------------------------------
 
 typedef void (*ImGuiContextHookCallback)(ImGuiContext* ctx, ImGuiContextHook* hook);
-enum ImGuiContextHookType { ImGuiContextHookType_NewFramePre, ImGuiContextHookType_NewFramePost, ImGuiContextHookType_EndFramePre, ImGuiContextHookType_EndFramePost, ImGuiContextHookType_RenderPre, ImGuiContextHookType_RenderPost, ImGuiContextHookType_Shutdown };
+enum ImGuiContextHookType { ImGuiContextHookType_NewFramePre, ImGuiContextHookType_NewFramePost, ImGuiContextHookType_EndFramePre, ImGuiContextHookType_EndFramePost, ImGuiContextHookType_RenderPre, ImGuiContextHookType_RenderPost, ImGuiContextHookType_Shutdown, ImGuiContextHookType_PendingRemoval_ };
 
 struct ImGuiContextHook
 {
+    ImGuiID                     HookId;     // A unique ID assigned by AddContextHook()
     ImGuiContextHookType        Type;
     ImGuiID                     Owner;
     ImGuiContextHookCallback    Callback;
@@ -1454,6 +1455,7 @@ struct ImGuiContext
     ImChunkStream<ImGuiWindowSettings>  SettingsWindows;        // ImGuiWindow .ini settings entries
     ImChunkStream<ImGuiTableSettings>   SettingsTables;         // ImGuiTable .ini settings entries
     ImVector<ImGuiContextHook>          Hooks;                  // Hooks for extensions (e.g. test engine)
+    ImGuiID                             HookIdNext;             // Next available HookId
 
     // Capture/Logging
     bool                    LogEnabled;                         // Currently capturing
@@ -2185,7 +2187,8 @@ namespace ImGui
     IMGUI_API void          UpdateMouseMovingWindowEndFrame();
 
     // Generic context hooks
-    IMGUI_API void          AddContextHook(ImGuiContext* context, const ImGuiContextHook* hook);
+    IMGUI_API ImGuiID       AddContextHook(ImGuiContext* context, const ImGuiContextHook* hook);
+    IMGUI_API void          RemoveContextHook(ImGuiContext* context, ImGuiID hook_to_remove);
     IMGUI_API void          CallContextHooks(ImGuiContext* context, ImGuiContextHookType type);
 
     // Settings