MultiSelect: made SetNextItemSelectionData() optional to allow disjoint selection (e.g. with a CollapsingHeader between items). Amend demo.
diff --git a/imgui.h b/imgui.h
index 987d7e7..6c65045 100644
--- a/imgui.h
+++ b/imgui.h
@@ -2766,14 +2766,14 @@
 //     1) Call BeginMultiSelect() with the last saved value of ->RangeSrc and its selection state.
 //        It is because you need to pass its selection state (and you own selection) that we don't store this value in Dear ImGui.
 //        (For the initial frame or when resetting your selection state: you may use the value for your first item or a "null" value that matches the type stored in your void*).
-//     2) Honor Clear/SelectAll requests by updating your selection data. Only required if you are using a clipper in step 4: but you can use same code as step 6 anyway.
+//     2) Honor Clear/SelectAll/SetRange requests by updating your selection data. (Only required if you are using a clipper in step 4: but you can use same code as step 6 anyway.)
 //   Loop
 //     3) Set RangeSrcPassedBy=true if the RangeSrc item is part of the items clipped before the first submitted/visible item. [Only required if you are using a clipper in step 4]
 //        This is because for range-selection we need to know if we are currently "inside" or "outside" the range.
 //        If you are using integer indices everywhere, this is easy to compute: if (clipper.DisplayStart > (int)data->RangeSrc) { data->RangeSrcPassedBy = true; }
 //     4) Submit your items with SetNextItemSelectionUserData() + Selectable()/TreeNode() calls.
 //        Call IsItemToggledSelection() to query if the selection state has been toggled, if you need the info immediately for your display (before EndMultiSelect()).
-//        When cannot return a "IsItemSelected()" value because we need to consider clipped/unprocessed items, this is why we return a "Toggle" event instead.
+//        When cannot provide a "IsItemSelected()" value because we need to consider clipped/unprocessed items, this is why we return a "Toggled" event instead.
 //   End
 //     5) Call EndMultiSelect(). Save the value of ->RangeSrc for the next frame (you may convert the value in a format that is safe for persistance)
 //     6) Honor Clear/SelectAll/SetRange requests by updating your selection data. Always process them in this order (as you will receive Clear+SetRange request simultaneously)
diff --git a/imgui_demo.cpp b/imgui_demo.cpp
index 3b98bc5..52e512e 100644
--- a/imgui_demo.cpp
+++ b/imgui_demo.cpp
@@ -2830,6 +2830,7 @@
             ImGui::TreePop();
         }
 
+        // Demonstrate implementation a most-basic form of multi-selection manually
         IMGUI_DEMO_MARKER("Widgets/Selection State/Multiple Selection (simplfied, manual)");
         if (ImGui::TreeNode("Multiple Selection (simplified, manual)"))
         {
@@ -2841,9 +2842,9 @@
                 sprintf(buf, "Object %d", n);
                 if (ImGui::Selectable(buf, selection[n]))
                 {
-                    if (!ImGui::GetIO().KeyCtrl)    // Clear selection when CTRL is not held
+                    if (!ImGui::GetIO().KeyCtrl) // Clear selection when CTRL is not held
                         memset(selection, 0, sizeof(selection));
-                    selection[n] ^= 1;
+                    selection[n] ^= 1; // Toggle current item
                 }
             }
             ImGui::TreePop();
@@ -2883,7 +2884,6 @@
                 {
                     char label[64];
                     sprintf(label, "Object %05d: %s", n, random_names[n % IM_ARRAYSIZE(random_names)]);
-
                     bool item_is_selected = selection.GetSelected(n);
                     ImGui::SetNextItemSelectionUserData(n);
                     ImGui::Selectable(label, item_is_selected);
@@ -2916,28 +2916,36 @@
             enum WidgetType { WidgetType_Selectable, WidgetType_TreeNode };
             static bool use_table = false;
             static bool use_drag_drop = true;
-            static bool multiple_selection_scopes = false;
+            static bool use_multiple_scopes = false;
+            static ImGuiMultiSelectFlags flags = ImGuiMultiSelectFlags_None;
             static WidgetType widget_type = WidgetType_TreeNode;
             if (ImGui::RadioButton("Selectables", widget_type == WidgetType_Selectable)) { widget_type = WidgetType_Selectable; }
             ImGui::SameLine();
             if (ImGui::RadioButton("Tree nodes", widget_type == WidgetType_TreeNode)) { widget_type = WidgetType_TreeNode; }
             ImGui::Checkbox("Use table", &use_table);
             ImGui::Checkbox("Use drag & drop", &use_drag_drop);
-            ImGui::Checkbox("Distinct selection scopes in same window", &multiple_selection_scopes);
+            ImGui::Checkbox("Multiple selection scopes in same window", &use_multiple_scopes);
+            ImGui::CheckboxFlags("ImGuiMultiSelectFlags_NoMultiSelect", &flags, ImGuiMultiSelectFlags_NoMultiSelect);
+            ImGui::CheckboxFlags("ImGuiMultiSelectFlags_NoUnselect", &flags, ImGuiMultiSelectFlags_NoUnselect);
+            ImGui::CheckboxFlags("ImGuiMultiSelectFlags_NoSelectAll", &flags, ImGuiMultiSelectFlags_NoSelectAll);
+            ImGui::CheckboxFlags("ImGuiMultiSelectFlags_ClearOnEscape", &flags, ImGuiMultiSelectFlags_ClearOnEscape);
+            ImGui::BeginDisabled(use_multiple_scopes);
+            ImGui::CheckboxFlags("ImGuiMultiSelectFlags_ClearOnClickWindowVoid", &flags, ImGuiMultiSelectFlags_ClearOnClickWindowVoid);
+            ImGui::EndDisabled();
 
-            // When 'multiple_selection_scopes' is set we show 3 selection scopes in the host window instead of 1 in a scrolling window.
+            // When 'use_multiple_scopes' is set we show 3 selection scopes in the host window instead of 1 in a scrolling window.
             static ExampleSelection selections_data[3];
-            const int selection_scope_count = multiple_selection_scopes ? 3 : 1;
+            const int selection_scope_count = use_multiple_scopes ? 3 : 1;
             for (int selection_scope_n = 0; selection_scope_n < selection_scope_count; selection_scope_n++)
             {
                 ExampleSelection* selection = &selections_data[selection_scope_n];
 
-                const int ITEMS_COUNT = multiple_selection_scopes ? 12 : 1000;
+                const int ITEMS_COUNT = use_multiple_scopes ? 12 : 1000; // Smaller count to make it easier to see multiple scopes in same screen.
                 ImGui::PushID(selection_scope_n);
 
                 // Open a scrolling region
                 bool draw_selection = true;
-                if (multiple_selection_scopes)
+                if (use_multiple_scopes)
                 {
                     ImGui::SeparatorText("Selection scope");
                 }
@@ -2952,15 +2960,13 @@
                     if (widget_type == WidgetType_TreeNode)
                         ImGui::PushStyleVar(ImGuiStyleVar_ItemSpacing, ImVec2(ImGui::GetStyle().ItemSpacing.x, 0.0f));
 
-                    ImGuiMultiSelectFlags flags = ImGuiMultiSelectFlags_None;
-                    if (multiple_selection_scopes)
-                        ;// flags |= ImGuiMultiSelectFlags_ClearOnClickRectVoid;
-                    else
-                        flags |= ImGuiMultiSelectFlags_ClearOnClickWindowVoid;
-                    ImGuiMultiSelectData* multi_select_data = ImGui::BeginMultiSelect(flags, (void*)(intptr_t)selection->RangeRef, selection->GetSelected(selection->RangeRef));
+                    ImGuiMultiSelectFlags local_flags = flags;
+                    if (use_multiple_scopes)
+                        local_flags &= ~ImGuiMultiSelectFlags_ClearOnClickWindowVoid; // local_flags |= ImGuiMultiSelectFlags_ClearOnClickRectVoid;
+                    ImGuiMultiSelectData* multi_select_data = ImGui::BeginMultiSelect(local_flags, (void*)(intptr_t)selection->RangeRef, selection->GetSelected(selection->RangeRef));
                     selection->ApplyRequests(multi_select_data, ITEMS_COUNT);
 
-                    if (multiple_selection_scopes)
+                    if (use_multiple_scopes)
                         ImGui::Text("Selection size: %d", selection->GetSelectionSize());   // Draw counter below Separator and after BeginMultiSelect()
 
                     if (use_table)
@@ -3062,7 +3068,7 @@
                     if (widget_type == WidgetType_TreeNode)
                         ImGui::PopStyleVar();
 
-                    if (multiple_selection_scopes == false)
+                    if (use_multiple_scopes == false)
                         ImGui::EndListBox();
                 }
                 ImGui::PopID(); // ImGui::PushID(selection_scope_n);
diff --git a/imgui_widgets.cpp b/imgui_widgets.cpp
index f1da8b1..4818539 100644
--- a/imgui_widgets.cpp
+++ b/imgui_widgets.cpp
@@ -6391,6 +6391,7 @@
 
     // Compute open and multi-select states before ItemAdd() as it clear NextItem data.
     bool is_open = TreeNodeUpdateNextOpen(storage_id, flags);
+    const bool is_multi_select = (g.NextItemData.Flags & ImGuiNextItemDataFlags_HasSelectionData) != 0; // Before ItemAdd()
     bool item_add = ItemAdd(interact_bb, id);
     g.LastItemData.StatusFlags |= ImGuiItemStatusFlags_HasDisplayRect;
     g.LastItemData.DisplayRect = frame_bb;
@@ -6464,7 +6465,6 @@
     const bool was_selected = selected;
 
     // Multi-selection support (header)
-    const bool is_multi_select = (g.MultiSelectState.Window == window);
     if (is_multi_select)
     {
         MultiSelectItemHeader(id, &selected);
@@ -6780,7 +6780,9 @@
     }
 
     const bool disabled_item = (flags & ImGuiSelectableFlags_Disabled) != 0;
+    const bool is_multi_select = (g.NextItemData.Flags & ImGuiNextItemDataFlags_HasSelectionData) != 0; // Before ItemAdd()
     const bool item_add = ItemAdd(bb, id, NULL, disabled_item ? (ImGuiItemFlags)ImGuiItemFlags_Disabled : ImGuiItemFlags_None);
+
     if (span_all_columns)
     {
         window->ClipRect.Min.x = backup_clip_rect_min_x;
@@ -6816,7 +6818,6 @@
     if ((flags & ImGuiSelectableFlags_AllowOverlap) || (g.LastItemData.InFlags & ImGuiItemFlags_AllowOverlap)) { button_flags |= ImGuiButtonFlags_AllowOverlap; }
 
     // Multi-selection support (header)
-    const bool is_multi_select = (g.MultiSelectState.Window == window);
     const bool was_selected = selected;
     if (is_multi_select)
     {
@@ -7166,7 +7167,7 @@
                 ms->In.RequestSelectAll = true;
 
         if (flags & ImGuiMultiSelectFlags_ClearOnEscape)
-            if (Shortcut(ImGuiKey_Escape))
+            if (Shortcut(ImGuiKey_Escape)) // FIXME-MULTISELECT: Only hog shortcut if selection is not null, meaning we need "has selection or "selection size" data here.
                 ms->In.RequestClear = true;
     }