MultiSelect: using ImGuiMultiSelectFlags_NoRangeSelect ensure never having to interpolate between two ImGuiSelectionUserData.

Author: ocornut

imgui.h

@@ -2760,6 +2760,8 @@ struct ImColor
 //   SetRange requests will give you two end-points and you will need to iterate/interpolate between them to update your selection.
 // - However it is perfectly possible to store a POINTER or another IDENTIFIER inside ImGuiSelectionUserData.
 //   Our system never assume that you identify items by indices, it never attempts to interpolate between two values.
+// - If you enable ImGuiMultiSelectFlags_NoRangeSelect then it is guaranteed that you will never have to interpolate
+//   between two ImGuiSelectionUserData, which may be a convenient way to use part of the feature with less code work.
 // - As most users will want to store an index, for convenience and to reduce confusion we use ImS64 instead of void*,
 //   being syntactically easier to downcast. Feel free to reinterpret_cast and store a pointer inside.
 
@@ -2769,7 +2771,7 @@ enum ImGuiMultiSelectFlags_
     ImGuiMultiSelectFlags_None                  = 0,
     ImGuiMultiSelectFlags_SingleSelect          = 1 << 0,   // Disable selecting more than one item. This is available to allow single-selection code to share same code/logic if desired. It essentially disables the main purpose of BeginMultiSelect() tho!
     ImGuiMultiSelectFlags_NoSelectAll           = 1 << 1,   // Disable CTRL+A shortcut to select all.
-    ImGuiMultiSelectFlags_NoRangeSelect         = 1 << 2,   // Disable Shift+selection mouse/keyboard support (useful for unordered 2D selection).
+    ImGuiMultiSelectFlags_NoRangeSelect         = 1 << 2,   // Disable Shift+selection mouse/keyboard support (useful for unordered 2D selection). With BoxSelect is also ensure contiguous SetRange requests are not combined into one. This allows not handling interpolation in SetRange requests.
     ImGuiMultiSelectFlags_NoAutoSelect          = 1 << 3,   // Disable selecting items when navigating (useful for e.g. supporting range-select in a list of checkboxes)
     ImGuiMultiSelectFlags_NoAutoClear           = 1 << 4,   // Disable clearing selection when navigating or selecting another one (generally used with ImGuiMultiSelectFlags_NoAutoSelect. useful for e.g. supporting range-select in a list of checkboxes)
     ImGuiMultiSelectFlags_NoAutoClearOnReselect = 1 << 5,   // Disable clearing selection when clicking/selecting an already selected item

imgui_widgets.cpp

@@ -7680,9 +7680,10 @@ void ImGui::MultiSelectItemFooter(ImGuiID id, bool* p_selected, bool* p_pressed)
                 {
                     selected = !selected;
                     ImGuiSelectionRequest req = { ImGuiSelectionRequestType_SetRange, selected, +1, item_data, item_data };
-                    ImGuiSelectionRequest* prev_req = (ms->IO.Requests.Size > 0) ? &ms->IO.Requests.Data[ms->IO.Requests.Size - 1] : NULL;
-                    if (prev_req && prev_req->Type == ImGuiSelectionRequestType_SetRange && prev_req->RangeLastItem == ms->BoxSelectLastitem && prev_req->Selected == selected)
-                        prev_req->RangeLastItem = item_data; // Merge span into same request
+                    // Merge continuous ranges (unless NoRangeSelect is set)
+                    ImGuiSelectionRequest* prev = ms->IO.Requests.Size > 0 ? &ms->IO.Requests.Data[ms->IO.Requests.Size - 1] : NULL;
+                    if (prev && prev->Type == ImGuiSelectionRequestType_SetRange && prev->RangeLastItem == ms->BoxSelectLastitem && prev->Selected == selected && (ms->Flags & ImGuiMultiSelectFlags_NoRangeSelect) == 0)
+                        prev->RangeLastItem = item_data; // Merge span into same request
                     else
                         ms->IO.Requests.push_back(req);
                 }