MultiSelect: Fix Selectable() ambiguous return value, clarify need to use IsItemToggledSelection().

imgui_demo.cpp

@@ -2901,7 +2901,8 @@ static void ShowDemoWindowMultiSelect()
                         ImGui::SetNextItemSelectionUserData(n);
                         if (widget_type == WidgetType_Selectable)
                         {
-                            if (ImGui::Selectable(label, item_is_selected))
+                            ImGui::Selectable(label, item_is_selected);
+                            if (ImGui::IsItemToggledSelection())
                                 selection.SetSelected(n, !item_is_selected);
                         }
                         else if (widget_type == WidgetType_TreeNode)

imgui_widgets.cpp

@@ -6904,8 +6904,9 @@ bool ImGui::Selectable(const char* label, bool selected, ImGuiSelectableFlags fl
     if (disabled_item && !disabled_global)
         EndDisabled();
 
+    // Users of BeginMultiSelect() scope: call ImGui::IsItemToggledSelection() to retrieve selection toggle. Selectable() returns a pressed state!
     IMGUI_TEST_ENGINE_ITEM_INFO(id, label, g.LastItemData.StatusFlags);
-    return pressed || (was_selected != selected); //-V1020
+    return pressed; //-V1020
 }
 
 bool ImGui::Selectable(const char* label, bool* p_selected, ImGuiSelectableFlags flags, const ImVec2& size_arg)
@@ -7144,6 +7145,7 @@ ImGuiMultiSelectData* ImGui::BeginMultiSelect(ImGuiMultiSelectFlags flags, void*
     }
 
     // Auto clear when using Navigation to move within the selection (we compare SelectScopeId so it possible to use multiple lists inside a same window)
+    // FIXME: Polling key mods after the fact (frame following the move request) is incorrect, but latching it would requires non-trivial change in MultiSelectItemFooter()
     if (g.NavJustMovedToId != 0 && g.NavJustMovedToFocusScopeId == ms->FocusScopeId && g.NavJustMovedToHasSelectionData)
     {
         if (g.IO.KeyShift)