Stack Tool: Docs (#4631) + also prevent Metrics window from displayin…

…g twice.

docs/CHANGELOG.txt

@@ -42,7 +42,7 @@ Breaking Changes:
 
 Other Changes:
 
-- Debug: Stack Tool: Added "Stack Tool" available in "Demo->Examples->Stack Tool", "Metrics->Tools",
+- Debug: Stack Tool: Added "Stack Tool" available in "Demo->Tools->Stack Tool", "Metrics->Tools",
   or by calling the ShowStackToolWindow() function. The tool run queries on hovered id to display
   details about individual components that were hashed to create an ID. It helps understanding
   the ID stack system and debugging potential ID collisions. (#4631) [@ocornut, @rokups]

docs/FAQ.md

@@ -23,7 +23,7 @@ or view this file with any Markdown viewer.
 | [I integrated Dear ImGui in my engine and some elements are clipping or disappearing when I move windows around...](#q-i-integrated-dear-imgui-in-my-engine-and-some-elements-are-clipping-or-disappearing-when-i-move-windows-around) |
 | [I integrated Dear ImGui in my engine and some elements are displaying outside their expected windows boundaries...](#q-i-integrated-dear-imgui-in-my-engine-and-some-elements-are-displaying-outside-their-expected-windows-boundaries) |
 | **Q&A: Usage** |
-| **[Why is my widget not reacting when I click on it?<br>How can I have widgets with an empty label?<br>How can I have multiple widgets with the same label?](#q-why-is-my-widget-not-reacting-when-i-click-on-it)** |
+| **[About the ID Stack system..<br>Why is my widget not reacting when I click on it?<br>How can I have widgets with an empty label?<br>How can I have multiple widgets with the same label?](#q-about-the-id-stack-system)** |
 | [How can I display an image? What is ImTextureID, how does it work?](#q-how-can-i-display-an-image-what-is-imtextureid-how-does-it-work)|
 | [How can I use my own math types instead of ImVec2/ImVec4?](#q-how-can-i-use-my-own-math-types-instead-of-imvec2imvec4) |
 | [How can I interact with standard C++ types (such as std::string and std::vector)?](#q-how-can-i-interact-with-standard-c-types-such-as-stdstring-and-stdvector) |
@@ -186,17 +186,23 @@ Refer to rendering backends in the [examples/](https://github.com/ocornut/imgui/
 
 # Q&A: Usage
 
+### Q: About the ID Stack system...
 ### Q: Why is my widget not reacting when I click on it?
 ### Q: How can I have widgets with an empty label?
 ### Q: How can I have multiple widgets with the same label?
 
 A primer on labels and the ID Stack...
 
-Dear ImGui internally need to uniquely identify UI elements.
+Dear ImGui internally needs to uniquely identify UI elements.
 Elements that are typically not clickable (such as calls to the Text functions) don't need an ID.
 Interactive widgets (such as calls to Button buttons) need a unique ID.
-Unique ID are used internally to track active widgets and occasionally associate state to widgets.
-Unique ID are implicitly built from the hash of multiple elements that identify the "path" to the UI element.
+
+**Unique ID are used internally to track active widgets and occasionally associate state to widgets.<BR>
+Unique ID are implicitly built from the hash of multiple elements that identify the "path" to the UI element.**
+
+Since Dear ImGui 1.85 you can use `Demo>Tools>Stack Tool` or call `ImGui::ShowStackToolWindow()`. The tool display intermediate values leading to the creation of a unique ID, making things easier to debug and understand.
+
+![Stack tool](https://user-images.githubusercontent.com/8225057/136235657-a0ea5665-dcd1-423f-9be6-dc3f8ced8f12.png)
 
 - Unique ID are often derived from a string label and at minimum scoped within their host window:
 ```cpp

imgui.cpp

@@ -11205,7 +11205,7 @@ void ImGui::ShowMetricsWindow(bool* p_open)
     if (cfg->ShowStackTool)
         ShowStackToolWindow(&cfg->ShowStackTool);
 
-    if (!Begin("Dear ImGui Metrics/Debugger", p_open))
+    if (!Begin("Dear ImGui Metrics/Debugger", p_open) || GetCurrentWindow()->BeginCount > 1)
     {
         End();
         return;