Nav: tabbing happen within FocusScope. ImGuiWindowFlags_NavFlattened make window inherit focus scope from parent.

imgui.cpp

@@ -6420,7 +6420,8 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
 
     // Add to focus scope stack
     // We intentionally set g.CurrentWindow to NULL to prevent usage until when the viewport is set, then will call SetCurrentWindow()
-    PushFocusScope(window->ID);
+    if ((flags & ImGuiWindowFlags_NavFlattened) == 0)
+        PushFocusScope(window->ID);
     window->NavRootFocusScopeId = g.CurrentFocusScopeId;
     g.CurrentWindow = NULL;
 
@@ -7061,7 +7062,8 @@ void ImGui::End()
     if (window->DC.CurrentColumns)
         EndColumns();
     PopClipRect();   // Inner window clip rectangle
-    PopFocusScope();
+    if ((window->Flags & ImGuiWindowFlags_NavFlattened) == 0)
+        PopFocusScope();
 
     // Stop logging
     if (!(window->Flags & ImGuiWindowFlags_ChildWindow))    // FIXME: add more options for scope of logging
@@ -9679,6 +9681,7 @@ bool ImGui::ItemAdd(const ImRect& bb, ImGuiID id, const ImRect* nav_bb_arg, ImGu
         // If we crash on a NULL g.NavWindow we need to fix the bug elsewhere.
         if (!(g.LastItemData.InFlags & ImGuiItemFlags_NoNav))
         {
+            // FIMXE-NAV: investigate changing the window tests into a simple 'if (g.NavFocusScopeId == g.CurrentFocusScopeId)' test.
             window->DC.NavLayersActiveMaskNext |= (1 << window->DC.NavLayerCurrent);
             if (g.NavId == id || g.NavAnyRequest)
                 if (g.NavWindow->RootWindowForNav == window->RootWindowForNav)
@@ -11310,6 +11313,8 @@ void ImGui::NavProcessItemForTabbingRequest(ImGuiID id, ImGuiItemFlags item_flag
     if ((move_flags & ImGuiNavMoveFlags_FocusApi) == 0)
         if (g.NavLayer != g.CurrentWindow->DC.NavLayerCurrent)
             return;
+    if (g.NavFocusScopeId != g.CurrentFocusScopeId)
+        return;
 
     // - Can always land on an item when using API call.
     // - Tabbing with _NavEnableKeyboard (space/enter/arrows): goes through every item.

imgui.h

@@ -1009,7 +1009,7 @@ enum ImGuiWindowFlags_
     ImGuiWindowFlags_NoInputs               = ImGuiWindowFlags_NoMouseInputs | ImGuiWindowFlags_NoNavInputs | ImGuiWindowFlags_NoNavFocus,
 
     // [Internal]
-    ImGuiWindowFlags_NavFlattened           = 1 << 23,  // [BETA] On child window: allow gamepad/keyboard navigation to cross over parent border to this child or between sibling child windows.
+    ImGuiWindowFlags_NavFlattened           = 1 << 23,  // [BETA] On child window: share focus scope, allow gamepad/keyboard navigation to cross over parent border to this child or between sibling child windows.
     ImGuiWindowFlags_ChildWindow            = 1 << 24,  // Don't use! For internal use by BeginChild()
     ImGuiWindowFlags_Tooltip                = 1 << 25,  // Don't use! For internal use by BeginTooltip()
     ImGuiWindowFlags_Popup                  = 1 << 26,  // Don't use! For internal use by BeginPopup()