Nav, IO: added undocumented ConfigNavEnableTabbing flag. (#9218)

diff --git a/imgui.cpp b/imgui.cpp
index 35c7a7a..5e03d0b 100644
--- a/imgui.cpp
+++ b/imgui.cpp

@@ -4219,6 +4219,7 @@
 
     // All platforms use Ctrl+Tab but Ctrl<>Super are swapped on Mac...
     // FIXME: Because this value is stored, it annoyingly interfere with toggling io.ConfigMacOSXBehaviors updating this..
+    ConfigNavEnableTabbing = true;
     ConfigNavWindowingWithGamepad = true;
     ConfigNavWindowingKeyNext = IO.ConfigMacOSXBehaviors ? (ImGuiMod_Super | ImGuiKey_Tab) : (ImGuiMod_Ctrl | ImGuiKey_Tab);
     ConfigNavWindowingKeyPrev = IO.ConfigMacOSXBehaviors ? (ImGuiMod_Super | ImGuiMod_Shift | ImGuiKey_Tab) : (ImGuiMod_Ctrl | ImGuiMod_Shift | ImGuiKey_Tab);
@@ -13978,7 +13979,7 @@
     ImGuiContext& g = *GImGui;
     ImGuiWindow* window = g.NavWindow;
     IM_ASSERT(g.NavMoveDir == ImGuiDir_None);
-    if (window == NULL || g.NavWindowingTarget != NULL || (window->Flags & ImGuiWindowFlags_NoNavInputs))
+    if (window == NULL || g.NavWindowingTarget != NULL || (window->Flags & ImGuiWindowFlags_NoNavInputs) || !g.ConfigNavEnableTabbing)
         return;
 
     const bool tab_pressed = IsKeyPressed(ImGuiKey_Tab, ImGuiInputFlags_Repeat, ImGuiKeyOwner_NoOwner) && !g.IO.KeyCtrl && !g.IO.KeyAlt;

diff --git a/imgui_internal.h b/imgui_internal.h
index d596db4..9220149 100644
--- a/imgui_internal.h
+++ b/imgui_internal.h

@@ -2369,10 +2369,15 @@
     bool                    NavJustMovedToIsTabbing;            // Copy of ImGuiNavMoveFlags_IsTabbing. Maybe we should store whole flags.
     bool                    NavJustMovedToHasSelectionData;     // Copy of move result's ItemFlags & ImGuiItemFlags_HasSelectionUserData). Maybe we should just store ImGuiNavItemData.
 
-    // Navigation: Windowing (Ctrl+Tab for list, or Menu button + keys or directional pads to move/resize)
+    // Navigation: extra config options (will be made public eventually)
+    // - Tabbing (Tab, Shift+Tab) and Windowing (Ctrl+Tab, Ctrl+Shift+Tab) are enabled REGARDLESS of ImGuiConfigFlags_NavEnableKeyboard being set.
+    // - Ctrl+Tab is reconfigurable because it is the only shortcut that may be polled when no window are focused. It also doesn't work e.g. Web platforms.
+    bool                    ConfigNavEnableTabbing;             // = true. Enable tabbing (Tab, Shift+Tab). PLEASE LET ME KNOW IF YOU USE THIS.
     bool                    ConfigNavWindowingWithGamepad;      // = true. Enable Ctrl+Tab by holding ImGuiKey_GamepadFaceLeft (== ImGuiKey_NavGamepadMenu). When false, the button may still be used to toggle Menu layer.
-    ImGuiKeyChord           ConfigNavWindowingKeyNext;          // = ImGuiMod_Ctrl | ImGuiKey_Tab (or ImGuiMod_Super | ImGuiKey_Tab on OS X). For reconfiguration (see #4828)
+    ImGuiKeyChord           ConfigNavWindowingKeyNext;          // = ImGuiMod_Ctrl | ImGuiKey_Tab (or ImGuiMod_Super | ImGuiKey_Tab on OS X). Set to 0 to disable. For reconfiguration (see #4828)
     ImGuiKeyChord           ConfigNavWindowingKeyPrev;          // = ImGuiMod_Ctrl | ImGuiMod_Shift | ImGuiKey_Tab (or ImGuiMod_Super | ImGuiMod_Shift | ImGuiKey_Tab on OS X)
+
+    // Navigation: Windowing (Ctrl+Tab for list, or Menu button + keys or directional pads to move/resize)
     ImGuiWindow*            NavWindowingTarget;                 // Target window when doing Ctrl+Tab (or Pad Menu + FocusPrev/Next), this window is temporarily displayed top-most!
     ImGuiWindow*            NavWindowingTargetAnim;             // Record of last valid NavWindowingTarget until DimBgRatio and NavWindowingHighlightAlpha becomes 0.0f, so the fade-out can stay on it.
     ImGuiWindow*            NavWindowingListWindow;             // Internal window actually listing the Ctrl+Tab contents