RangeSelect/MultiSelect: Added IMGUI_HAS_MULTI_SELECT define. Fixed right-click toggling selection without clearing active id, could lead to MarkItemEdited() asserting. Fixed demo.

imgui.h

@@ -2659,6 +2659,8 @@ struct ImColor
 // [SECTION] Multi-Select API flags and structures (ImGuiMultiSelectFlags, ImGuiMultiSelectData)
 //-----------------------------------------------------------------------------
 
+#define IMGUI_HAS_MULTI_SELECT      // Multi-Select/Range-Select WIP branch // <-- This is currently _not_ in the top of imgui.h to prevent merge conflicts.
+
 // Flags for BeginMultiSelect().
 // This system is designed to allow mouse/keyboard multi-selection, including support for range-selection (SHIFT + click) which is difficult to re-implement manually.
 // If you disable multi-selection with ImGuiMultiSelectFlags_NoMultiSelect (which is provided for consistency and flexibility), the whole BeginMultiSelect() system

imgui_internal.h

@@ -1710,7 +1710,6 @@ struct ImGuiOldColumns
 // We always assume that -1 is an invalid value (which works for indices and pointers)
 #define ImGuiSelectionUserData_Invalid        ((ImGuiSelectionUserData)-1)
 
-#define IMGUI_HAS_MULTI_SELECT 1
 #ifdef IMGUI_HAS_MULTI_SELECT
 
 struct IMGUI_API ImGuiMultiSelectState

imgui_widgets.cpp

@@ -7141,7 +7141,9 @@ void ImGui::MultiSelectItemFooter(ImGuiID id, bool* p_selected, bool* p_pressed)
     bool hovered = IsItemHovered(ImGuiHoveredFlags_AllowWhenBlockedByPopup);
     if (hovered && IsMouseClicked(1))
     {
-        SetFocusID(g.LastItemData.ID, window);
+        if (g.ActiveId != 0 && g.ActiveId != id)
+            ClearActiveID();
+        SetFocusID(id, window);
         if (!pressed && !selected)
         {
             pressed = true;