Added an assertion for the common user mistake of using "" as an identifier at the root level of a window. (#1414, #2562, #2807, #4008, #4158, #4375, #4548, #4657, #4796)

#4158, #4375, #4548, #4657, #4796)

docs/CHANGELOG.txt

@@ -110,6 +110,10 @@ Breaking Changes:
 
 Other Changes:
 
+- Added an assertion for the common user mistake of using "" as an identifier at the root level of a window
+  instead of using "##something". Empty identifiers are valid and useful in a very small amount of cases,
+  but 99.9% of the time if you need an empty label you should use "##something". (#1414, #2562, #2807, #4008,
+  #4158, #4375, #4548, #4657, #4796). READ THE FAQ ABOUT HOW THE ID STACK WORKS -> https://dearimgui.org/faq
 - Added GetMouseClickedCount() function, returning the number of successive clicks. (#3229) [@kudaba]
   (so IsMouseDoubleClicked(ImGuiMouseButton_Left) is same as GetMouseClickedCount(ImGuiMouseButton_Left) == 2,
   but it allows testing for triple clicks and more).

imgui.cpp

@@ -8379,6 +8379,11 @@ bool ImGui::ItemAdd(const ImRect& bb, ImGuiID id, const ImRect* nav_bb_arg, ImGu
                 if (window == g.NavWindow || ((window->Flags | g.NavWindow->Flags) & ImGuiWindowFlags_NavFlattened))
                     NavProcessItem();
 
+        // [DEBUG] People keep stumbling on this problem and using "" as identifier in the root of a window instead of "##something".
+        // Empty identifier are valid and useful in a small amount of cases, but 99.9% of the time you want to use "##something".
+        // READ THE FAQ: https://dearimgui.org/faq
+        IM_ASSERT(id != window->ID && "Cannot have an empty ID at the root of a window. If you need an empty label, use ## and read the FAQ about how the ID Stack works!");
+
         // [DEBUG] Item Picker tool, when enabling the "extended" version we perform the check in ItemAdd()
 #ifdef IMGUI_DEBUG_TOOL_ITEM_PICKER_EX
         if (id == g.DebugItemPickerBreakId)