Menus: Separate menu sets by nav layer. (#3496, #4797) + Demo: Remove incorrect and useless suggestion to use PushID().

Fixes a common case where opening menu in one nav layer and hovering a menu in another nav layer would open that menu without a click.

docs/CHANGELOG.txt

@@ -101,6 +101,8 @@ Other Changes:
 - Menus: Adjusted BeginMenu() closing logic so hovering void or non-MenuItem() in parent window
   always lead to menu closure. Fixes using items that are not MenuItem() or BeginItem() at the root
   level of a popup with a child menu opened.
+- Menus: Menus emitted from the main/scrolling layer are not part of the same menuset as menus emitted
+  from the menu-bar, avoiding  accidental hovering from one to the other. (#3496, #4797) [@rokups]
 - Stack Tool: Added option to copy item path to clipboard. (#4631)
 - Settings: Fixed out-of-bounds read when .ini file on disk is empty. (#5351) [@quantum5]
 - DrawList: Fixed PathArcTo() emitting terminating vertices too close to arc vertices. (#4993) [@thedmd]

imgui.cpp

@@ -6071,6 +6071,7 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
     {
         ImGuiPopupData& popup_ref = g.OpenPopupStack[g.BeginPopupStack.Size];
         popup_ref.Window = window;
+        popup_ref.ParentNavLayer = parent_window_in_stack->DC.NavLayerCurrent;
         g.BeginPopupStack.push_back(popup_ref);
         window->PopupId = popup_ref.PopupId;
     }

imgui_demo.cpp

@@ -3546,19 +3546,12 @@ static void ShowDemoWindowPopups()
         ImGui::TextWrapped("Below we are testing adding menu items to a regular window. It's rather unusual but should work!");
         ImGui::Separator();
 
-        // Note: As a quirk in this very specific example, we want to differentiate the parent of this menu from the
-        // parent of the various popup menus above. To do so we are encloding the items in a PushID()/PopID() block
-        // to make them two different menusets. If we don't, opening any popup above and hovering our menu here would
-        // open it. This is because once a menu is active, we allow to switch to a sibling menu by just hovering on it,
-        // which is the desired behavior for regular menus.
-        ImGui::PushID("foo");
         ImGui::MenuItem("Menu item", "CTRL+M");
         if (ImGui::BeginMenu("Menu inside a regular window"))
         {
             ShowExampleMenuFile();
             ImGui::EndMenu();
         }
-        ImGui::PopID();
         ImGui::Separator();
         ImGui::TreePop();
     }

imgui_internal.h

@@ -1038,12 +1038,13 @@ struct ImGuiPopupData
     ImGuiID             PopupId;        // Set on OpenPopup()
     ImGuiWindow*        Window;         // Resolved on BeginPopup() - may stay unresolved if user never calls OpenPopup()
     ImGuiWindow*        SourceWindow;   // Set on OpenPopup() copy of NavWindow at the time of opening the popup
+    int                 ParentNavLayer; // Resolved on BeginPopup(). Actually a ImGuiNavLayer type (declared down below), initialized to -1 which is not part of an enum, but serves well-enough as "not any of layers" value
     int                 OpenFrameCount; // Set on OpenPopup()
     ImGuiID             OpenParentId;   // Set on OpenPopup(), we need this to differentiate multiple menu sets from each others (e.g. inside menu bar vs loose menu items)
     ImVec2              OpenPopupPos;   // Set on OpenPopup(), preferred popup position (typically == OpenMousePos when using mouse)
     ImVec2              OpenMousePos;   // Set on OpenPopup(), copy of mouse position at the time of opening popup
 
-    ImGuiPopupData()    { memset(this, 0, sizeof(*this)); OpenFrameCount = -1; }
+    ImGuiPopupData()    { memset(this, 0, sizeof(*this)); ParentNavLayer = OpenFrameCount = -1; }
 };
 
 enum ImGuiNextWindowDataFlags_

imgui_widgets.cpp

@@ -6939,14 +6939,19 @@ static bool IsRootOfOpenMenuSet()
     if ((g.OpenPopupStack.Size <= g.BeginPopupStack.Size) || (window->Flags & ImGuiWindowFlags_ChildMenu))
         return false;
 
-    // Initially we used 'OpenParentId' to differentiate multiple menu sets from each others (e.g. inside menu bar vs loose menu items) based on parent ID.
+    // Initially we used 'upper_popup->OpenParentId == window->IDStack.back()' to differentiate multiple menu sets from each others
+    // (e.g. inside menu bar vs loose menu items) based on parent ID.
     // This would however prevent the use of e.g. PuhsID() user code submitting menus.
     // Previously this worked between popup and a first child menu because the first child menu always had the _ChildWindow flag,
     // making  hovering on parent popup possible while first child menu was focused - but this was generally a bug with other side effects.
     // Instead we don't treat Popup specifically (in order to consistently support menu features in them), maybe the first child menu of a Popup
-    // doesn't have the _ChildWindow flag, and we rely on this IsRootOfOpenMenuSet() check to allow hovering between root window/popup and first chilld menu.
+    // doesn't have the _ChildWindow flag, and we rely on this IsRootOfOpenMenuSet() check to allow hovering between root window/popup and first child menu.
+    // In the end, lack of ID check made it so we could no longer differentiate between separate menu sets. To compensate for that, we at least check parent window nav layer.
+    // This fixes the most common case of menu opening on hover when moving between window content and menu bar. Multiple different menu sets in same nav layer would still
+    // open on hover, but that should be a lesser problem, because if such menus are close in proximity in window content then it won't feel weird and if they are far apart
+    // it likely won't be a problem anyone runs into.
     const ImGuiPopupData* upper_popup = &g.OpenPopupStack[g.BeginPopupStack.Size];
-    return (/*upper_popup->OpenParentId == window->IDStack.back() &&*/ upper_popup->Window && (upper_popup->Window->Flags & ImGuiWindowFlags_ChildMenu));
+    return (window->DC.NavLayerCurrent == upper_popup->ParentNavLayer && upper_popup->Window && (upper_popup->Window->Flags & ImGuiWindowFlags_ChildMenu));
 }
 
 bool ImGui::BeginMenuEx(const char* label, const char* icon, bool enabled)