Internals: rework FocusScope system, current scope doesn't need to be in window + child doesn't inherit.

Intended as part of work for input routing + blind menu processing shortcuts. Some of this commit will be stripped by next commit.
Intent was to sort windows along with focus scope to build a hierarchy, but for our needs we'd need a persistant one, so scrapping the idea. Not squashing this with next commit to keep a bit of history for future references.

imgui.cpp

@@ -6319,10 +6319,23 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
     window_stack_data.ParentLastItemDataBackup = g.LastItemData;
     window_stack_data.StackSizesOnBegin.SetToCurrentState();
     g.CurrentWindowStack.push_back(window_stack_data);
-    g.CurrentWindow = NULL;
     if (flags & ImGuiWindowFlags_ChildMenu)
         g.BeginMenuCount++;
 
+    // Update ->RootWindow and others pointers (before any possible call to FocusWindow)
+    if (first_begin_of_the_frame)
+    {
+        UpdateWindowParentAndRootLinks(window, flags, parent_window);
+        window->ParentWindowInBeginStack = parent_window_in_stack;
+    }
+
+    // Add to focus scope stack - inherited by default by child windows from parent, reset by regular window
+    //if (window == window->RootWindow && (window->Flags & ImGuiWindowFlags_ChildMenu) == 0)
+        PushFocusScope(window->ID);
+    window->NavRootFocusScopeId = g.CurrentFocusScopeId;
+    g.CurrentWindow = NULL;
+
+    // Add to popup stack
     if (flags & ImGuiWindowFlags_Popup)
     {
         ImGuiPopupData& popup_ref = g.OpenPopupStack[g.BeginPopupStack.Size];
@@ -6332,13 +6345,6 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
         window->PopupId = popup_ref.PopupId;
     }
 
-    // Update ->RootWindow and others pointers (before any possible call to FocusWindow)
-    if (first_begin_of_the_frame)
-    {
-        UpdateWindowParentAndRootLinks(window, flags, parent_window);
-        window->ParentWindowInBeginStack = parent_window_in_stack;
-    }
-
     // Process SetNextWindow***() calls
     // (FIXME: Consider splitting the HasXXX flags into X/Y components
     bool window_pos_set_by_api = false;
@@ -6859,9 +6865,6 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
         SetCurrentWindow(window);
     }
 
-    // Pull/inherit current state
-    window->DC.NavFocusScopeIdCurrent = (flags & ImGuiWindowFlags_ChildWindow) ? parent_window->DC.NavFocusScopeIdCurrent : window->GetID("#FOCUSSCOPE"); // Inherit from parent only // -V595
-
     PushClipRect(window->InnerClipRect.Min, window->InnerClipRect.Max, true);
 
     // Clear 'accessed' flag last thing (After PushClipRect which will set the flag. We want the flag to stay false when the default "Debug" window is unused)
@@ -6939,6 +6942,8 @@ void ImGui::End()
     if (window->DC.CurrentColumns)
         EndColumns();
     PopClipRect();   // Inner window clip rectangle
+    //if (window == window->RootWindow && (window->Flags & ImGuiWindowFlags_ChildMenu) == 0)
+        PopFocusScope();
 
     // Stop logging
     if (!(window->Flags & ImGuiWindowFlags_ChildWindow))    // FIXME: add more options for scope of logging
@@ -7048,7 +7053,7 @@ void ImGui::FocusWindow(ImGuiWindow* window)
             g.NavMousePosDirty = true;
         g.NavId = window ? window->NavLastIds[0] : 0; // Restore NavId
         g.NavLayer = ImGuiNavLayer_Main;
-        g.NavFocusScopeId = 0;
+        g.NavFocusScopeId = window ? window->NavRootFocusScopeId : 0;
         g.NavIdIsAlive = false;
 
         // Close popups if any
@@ -7619,18 +7624,24 @@ void ImGui::ActivateItem(ImGuiID id)
 void ImGui::PushFocusScope(ImGuiID id)
 {
     ImGuiContext& g = *GImGui;
-    ImGuiWindow* window = g.CurrentWindow;
-    g.FocusScopeStack.push_back(window->DC.NavFocusScopeIdCurrent);
-    window->DC.NavFocusScopeIdCurrent = id;
+    if (g.FocusScopeStackLocked > 0)
+        return;
+    ImGuiFocusScope scope;
+    scope.FocusScopeId = id;
+    scope.Window = g.CurrentWindow;
+    g.FocusScopeStack.push_back(scope);
+    g.CurrentFocusScopeId = scope.FocusScopeId;
 }
 
 void ImGui::PopFocusScope()
 {
     ImGuiContext& g = *GImGui;
-    ImGuiWindow* window = g.CurrentWindow;
+    if (g.FocusScopeStackLocked > 0)
+        return;
     IM_ASSERT(g.FocusScopeStack.Size > 0); // Too many PopFocusScope() ?
-    window->DC.NavFocusScopeIdCurrent = g.FocusScopeStack.back();
+    IM_ASSERT(g.FocusScopeStack.back().Window == g.CurrentWindow); // Mismatched pop location?
     g.FocusScopeStack.pop_back();
+    g.CurrentFocusScopeId = g.FocusScopeStack.Size ? g.FocusScopeStack.back().FocusScopeId : 0;
 }
 
 // Note: this will likely be called ActivateItem() once we rework our Focus/Activation system!
@@ -8509,7 +8520,7 @@ void    ImGui::ErrorCheckEndWindowRecover(ImGuiErrorLogCallback log_callback, vo
         if (log_callback) log_callback(user_data, "Recovered from missing PopStyleVar() in '%s'", window->Name);
         PopStyleVar();
     }
-    while (g.FocusScopeStack.Size > stack_sizes->SizeOfFocusScopeStack) //-V1044
+    while (g.FocusScopeStack.Size > stack_sizes->SizeOfFocusScopeStack + 1) //-V1044
     {
         if (log_callback) log_callback(user_data, "Recovered from missing PopFocusScope() in '%s'", window->Name);
         PopFocusScope();
@@ -9953,12 +9964,12 @@ void ImGui::SetFocusID(ImGuiID id, ImGuiWindow* window)
     if (g.NavWindow != window)
        SetNavWindow(window);
 
-    // Assume that SetFocusID() is called in the context where its window->DC.NavLayerCurrent and window->DC.NavFocusScopeIdCurrent are valid.
+    // Assume that SetFocusID() is called in the context where its window->DC.NavLayerCurrent and g.CurrentFocusScopeId are valid.
     // Note that window may be != g.CurrentWindow (e.g. SetFocusID call in InputTextEx for multi-line text)
     const ImGuiNavLayer nav_layer = window->DC.NavLayerCurrent;
     g.NavId = id;
     g.NavLayer = nav_layer;
-    g.NavFocusScopeId = window->DC.NavFocusScopeIdCurrent;
+    g.NavFocusScopeId = g.CurrentFocusScopeId;
     window->NavLastIds[nav_layer] = id;
     if (g.LastItemData.ID == id)
         window->NavRectRel[nav_layer] = WindowRectAbsToRel(window, g.LastItemData.NavRect);
@@ -10139,7 +10150,7 @@ static void ImGui::NavApplyItemToResult(ImGuiNavItemData* result)
     ImGuiWindow* window = g.CurrentWindow;
     result->Window = window;
     result->ID = g.LastItemData.ID;
-    result->FocusScopeId = window->DC.NavFocusScopeIdCurrent;
+    result->FocusScopeId = g.CurrentFocusScopeId;
     result->InFlags = g.LastItemData.InFlags;
     result->RectRel = WindowRectAbsToRel(window, g.LastItemData.NavRect);
 }
@@ -10206,7 +10217,7 @@ static void ImGui::NavProcessItem()
         if (g.NavWindow != window)
             SetNavWindow(window); // Always refresh g.NavWindow, because some operations such as FocusItem() may not have a window.
         g.NavLayer = window->DC.NavLayerCurrent;
-        g.NavFocusScopeId = window->DC.NavFocusScopeIdCurrent;
+        g.NavFocusScopeId = g.CurrentFocusScopeId;
         g.NavIdIsAlive = true;
         window->NavRectRel[window->DC.NavLayerCurrent] = WindowRectAbsToRel(window, nav_bb);    // Store item bounding box (relative to window position)
     }
@@ -10394,7 +10405,8 @@ void ImGui::NavInitWindow(ImGuiWindow* window, bool force_reinit)
 
     if (window->Flags & ImGuiWindowFlags_NoNavInputs)
     {
-        g.NavId = g.NavFocusScopeId = 0;
+        g.NavId = 0;
+        g.NavFocusScopeId = window->NavRootFocusScopeId;
         return;
     }
 
@@ -10404,7 +10416,7 @@ void ImGui::NavInitWindow(ImGuiWindow* window, bool force_reinit)
     IMGUI_DEBUG_LOG_NAV("[nav] NavInitRequest: from NavInitWindow(), init_for_nav=%d, window=\"%s\", layer=%d\n", init_for_nav, window->Name, g.NavLayer);
     if (init_for_nav)
     {
-        SetNavID(0, g.NavLayer, 0, ImRect());
+        SetNavID(0, g.NavLayer, window->NavRootFocusScopeId, ImRect());
         g.NavInitRequest = true;
         g.NavInitRequestFromMove = false;
         g.NavInitResultId = 0;
@@ -10414,7 +10426,7 @@ void ImGui::NavInitWindow(ImGuiWindow* window, bool force_reinit)
     else
     {
         g.NavId = window->NavLastIds[0];
-        g.NavFocusScopeId = 0;
+        g.NavFocusScopeId = window->NavRootFocusScopeId;
     }
 }
 
@@ -10738,7 +10750,7 @@ void ImGui::NavUpdateCreateMoveRequest()
             inner_rect_rel.Min.y = clamp_y ? (inner_rect_rel.Min.y + pad_y) : -FLT_MAX;
             inner_rect_rel.Max.y = clamp_y ? (inner_rect_rel.Max.y - pad_y) : +FLT_MAX;
             window->NavRectRel[g.NavLayer].ClipWithFull(inner_rect_rel);
-            g.NavId = g.NavFocusScopeId = 0;
+            g.NavId = /*g.NavFocusScopeId =*/ 0;
         }
     }
 
@@ -10921,7 +10933,7 @@ static void ImGui::NavUpdateCancelRequest()
         // Clear NavLastId for popups but keep it for regular child window so we can leave one and come back where we were
         if (g.NavWindow && ((g.NavWindow->Flags & ImGuiWindowFlags_Popup) || !(g.NavWindow->Flags & ImGuiWindowFlags_ChildWindow)))
             g.NavWindow->NavLastIds[0] = 0;
-        g.NavId = g.NavFocusScopeId = 0;
+        g.NavId = /*g.NavFocusScopeId =*/ 0;
     }
 }
 

imgui.h

@@ -23,7 +23,7 @@
 // Library Version
 // (Integer encoded as XYYZZ for use in #if preprocessor conditionals, e.g. '#if IMGUI_VERSION_NUM > 12345')
 #define IMGUI_VERSION               "1.89 WIP"
-#define IMGUI_VERSION_NUM           18834
+#define IMGUI_VERSION_NUM           18835
 #define IMGUI_HAS_TABLE
 
 /*

imgui_internal.h

@@ -1388,6 +1388,14 @@ struct ImGuiNavItemData
     void Clear()        { Window = NULL; ID = FocusScopeId = 0; InFlags = 0; DistBox = DistCenter = DistAxial = FLT_MAX; }
 };
 
+struct ImGuiFocusScope
+{
+    ImGuiID             FocusScopeId;
+    ImGuiWindow*        Window;
+
+    ImGuiFocusScope()   { memset(this, 0, sizeof(*this)); }
+};
+
 //-----------------------------------------------------------------------------
 // [SECTION] Columns support
 //-----------------------------------------------------------------------------
@@ -1688,6 +1696,7 @@ struct ImGuiContext
 #endif
 
     // Next window/item data
+    ImGuiID                 CurrentFocusScopeId;                // == g.FocusScopeStack.back().FocusScopeId
     ImGuiItemFlags          CurrentItemFlags;                   // == g.ItemFlagsStack.back()
     ImGuiNextItemData       NextItemData;                       // Storage for SetNextItem** functions
     ImGuiLastItemData       LastItemData;                       // Storage for last submitted item (setup by ItemAdd)
@@ -1697,12 +1706,13 @@ struct ImGuiContext
     ImVector<ImGuiColorMod> ColorStack;                         // Stack for PushStyleColor()/PopStyleColor() - inherited by Begin()
     ImVector<ImGuiStyleMod> StyleVarStack;                      // Stack for PushStyleVar()/PopStyleVar() - inherited by Begin()
     ImVector<ImFont*>       FontStack;                          // Stack for PushFont()/PopFont() - inherited by Begin()
-    ImVector<ImGuiID>       FocusScopeStack;                    // Stack for PushFocusScope()/PopFocusScope() - not inherited by Begin(), unless child window
+    ImVector<ImGuiFocusScope> FocusScopeStack;                  // Stack for PushFocusScope()/PopFocusScope() - inherited by BeginChild(), pushed into by Begin()
     ImVector<ImGuiItemFlags>ItemFlagsStack;                     // Stack for PushItemFlag()/PopItemFlag() - inherited by Begin()
     ImVector<ImGuiGroupData>GroupStack;                         // Stack for BeginGroup()/EndGroup() - not inherited by Begin()
     ImVector<ImGuiPopupData>OpenPopupStack;                     // Which popups are open (persistent)
     ImVector<ImGuiPopupData>BeginPopupStack;                    // Which level of BeginPopup() we are in (reset every frame)
     int                     BeginMenuCount;
+    int                     FocusScopeStackLocked;              // Prevent PushFocusScope()/PopFocusScope()
 
     // Viewports
     ImVector<ImGuiViewportP*> Viewports;                        // Active viewports (Size==1 in 'master' branch). Each viewports hold their copy of ImDrawData.
@@ -1937,8 +1947,10 @@ struct ImGuiContext
         ActiveIdUsingNavInputMask = 0x00;
 #endif
 
+        CurrentFocusScopeId = 0;
         CurrentItemFlags = ImGuiItemFlags_None;
         BeginMenuCount = 0;
+        FocusScopeStackLocked = 0;
 
         NavWindow = NULL;
         NavId = NavFocusScopeId = NavActivateId = NavActivateDownId = NavActivatePressedId = NavActivateInputId = 0;
@@ -2068,7 +2080,6 @@ struct IMGUI_API ImGuiWindowTempData
     ImGuiNavLayer           NavLayerCurrent;        // Current layer, 0..31 (we currently only use 0..1)
     short                   NavLayersActiveMask;    // Which layers have been written to (result from previous frame)
     short                   NavLayersActiveMaskNext;// Which layers have been written to (accumulator for current frame)
-    ImGuiID                 NavFocusScopeIdCurrent; // Current focus scope ID while appending
     bool                    NavHideHighlightOneFrame;
     bool                    NavHasScroll;           // Set when scrolling can be used (ScrollMax > 0.0f)
 
@@ -2186,6 +2197,7 @@ struct IMGUI_API ImGuiWindow
     ImGuiWindow*            NavLastChildNavWindow;              // When going to the menu bar, we remember the child window we came from. (This could probably be made implicit if we kept g.Windows sorted by last focused including child window.)
     ImGuiID                 NavLastIds[ImGuiNavLayer_COUNT];    // Last known NavId for this window, per layer (0/1)
     ImRect                  NavRectRel[ImGuiNavLayer_COUNT];    // Reference rectangle, in window relative space
+    ImGuiID                 NavRootFocusScopeId;                // Focus Scope ID at the time of Begin()
 
     int                     MemoryDrawListIdxCapacity;          // Backup of last idx/vtx count, so when waking up the window we can preallocate and avoid iterative alloc/copy
     int                     MemoryDrawListVtxCapacity;
@@ -2725,14 +2737,6 @@ namespace ImGui
     IMGUI_API void          SetNavWindow(ImGuiWindow* window);
     IMGUI_API void          SetNavID(ImGuiID id, ImGuiNavLayer nav_layer, ImGuiID focus_scope_id, const ImRect& rect_rel);
 
-    // Focus Scope (WIP)
-    // This is generally used to identify a selection set (multiple of which may be in the same window), as selection
-    // patterns generally need to react (e.g. clear selection) when landing on an item of the set.
-    IMGUI_API void          PushFocusScope(ImGuiID id);
-    IMGUI_API void          PopFocusScope();
-    inline ImGuiID          GetFocusedFocusScope()          { ImGuiContext& g = *GImGui; return g.NavFocusScopeId; }                            // Focus scope which is actually active
-    inline ImGuiID          GetFocusScope()                 { ImGuiContext& g = *GImGui; return g.CurrentWindow->DC.NavFocusScopeIdCurrent; }   // Focus scope we are outputting into, set by PushFocusScope()
-
     // Inputs
     // FIXME: Eventually we should aim to move e.g. IsActiveIdUsingKey() into IsKeyXXX functions.
     inline bool             IsNamedKey(ImGuiKey key)                                    { return key >= ImGuiKey_NamedKey_BEGIN && key < ImGuiKey_NamedKey_END; }
@@ -2767,6 +2771,18 @@ namespace ImGui
     inline bool             IsKeyPressedMap(ImGuiKey key, bool repeat = true)           { IM_ASSERT(IsNamedKey(key)); return IsKeyPressed(key, repeat); } // [removed in 1.87]
 #endif
 
+    // [EXPERIMENTAL] Focus Scope
+    // This is generally used to identify a unique input location (for e.g. a selection set)
+    // There is one per window (automatically set in Begin), but:
+    // - Selection patterns generally need to react (e.g. clear a selection) when landing on one item of the set.
+    //   So in order to identify a set multiple lists in same window may each need a focus scope.
+    //   If you imagine an hypothetical BeginSelectionGroup()/EndSelectionGroup() api, it would likely call PushFocusScope()/EndFocusScope()
+    // - Shortcut routing also use focus scope as a default location identifier if an owner is not provided.
+    // We don't use the ID Stack for this as it is common to want them separate.
+    IMGUI_API void          PushFocusScope(ImGuiID id);
+    IMGUI_API void          PopFocusScope();
+    inline ImGuiID          GetCurrentFocusScope() { ImGuiContext& g = *GImGui; return g.CurrentFocusScopeId; }   // Focus scope we are outputting into, set by PushFocusScope()
+
     // Drag and Drop
     IMGUI_API bool          IsDragDropActive();
     IMGUI_API bool          BeginDragDropTargetCustom(const ImRect& bb, ImGuiID id);

imgui_widgets.cpp

@@ -6329,7 +6329,7 @@ bool ImGui::Selectable(const char* label, bool selected, ImGuiSelectableFlags fl
     //   - (1) it would require focus scope to be set, need exposing PushFocusScope() or equivalent (e.g. BeginSelection() calling PushFocusScope())
     //   - (2) usage will fail with clipped items
     //   The multi-select API aim to fix those issues, e.g. may be replaced with a BeginSelection() API.
-    if ((flags & ImGuiSelectableFlags_SelectOnNav) && g.NavJustMovedToId != 0 && g.NavJustMovedToFocusScopeId == window->DC.NavFocusScopeIdCurrent)
+    if ((flags & ImGuiSelectableFlags_SelectOnNav) && g.NavJustMovedToId != 0 && g.NavJustMovedToFocusScopeId == g.CurrentFocusScopeId)
         if (g.NavJustMovedToId == id)
             selected = pressed = true;
 
@@ -6338,7 +6338,7 @@ bool ImGui::Selectable(const char* label, bool selected, ImGuiSelectableFlags fl
     {
         if (!g.NavDisableMouseHover && g.NavWindow == window && g.NavLayer == window->DC.NavLayerCurrent)
         {
-            SetNavID(id, window->DC.NavLayerCurrent, window->DC.NavFocusScopeIdCurrent, WindowRectAbsToRel(window, bb)); // (bb == NavRect)
+            SetNavID(id, window->DC.NavLayerCurrent, g.CurrentFocusScopeId, WindowRectAbsToRel(window, bb)); // (bb == NavRect)
             g.NavDisableHighlight = true;
         }
     }