Method ApplyRequests

external/imgui/imgui_widgets.cpp:8688–8744

Apply requests coming from BeginMultiSelect() and EndMultiSelect(). - Enable 'Demo->Tools->Debug Log->Selection' to see selection requests as they happen. - Honoring SetRange requests requires that you can iterate/interpolate between RangeFirstItem and RangeLastItem. - In this demo we often submit indices to SetNextItemSelectionUserData() + store the same indices in persistent selection. - Your co

//      if (req.Type == ImGuiSelectionRequestType_SetRange)  { for (int n = (int)ms_io->RangeFirstItem; n <= (int)ms_io->RangeLastItem; n++) { SetItemSelected(n, ms_io->Selected); } }
//   }
void ImGuiSelectionBasicStorage::ApplyRequests(ImGuiMultiSelectIO* ms_io)
{
    // For convenience we obtain ItemsCount as passed to BeginMultiSelect(), which is optional.
    // It makes sense when using ImGuiSelectionBasicStorage to simply pass your items count to BeginMultiSelect().
    // Other scheme may handle SetAll differently.
    IM_ASSERT(ms_io->ItemsCount != -1 && "Missing value for items_count in BeginMultiSelect() call!");
    IM_ASSERT(AdapterIndexToStorageId != NULL);

    // This is optimized/specialized to cope with very large selections (e.g. 100k+ items)
    // - A simpler version could call SetItemSelected() directly instead of ImGuiSelectionBasicStorage_BatchSetItemSelected() + ImGuiSelectionBasicStorage_BatchFinish().
    // - Optimized select can append unsorted, then sort in a second pass. Optimized unselect can clear in-place then compact in a second pass.
    // - A more optimal version wouldn't even use ImGuiStorage but directly a ImVector<ImGuiID> to reduce bandwidth, but this is a reasonable trade off to reuse code.
    // - There are many ways this could be better optimized. The worse case scenario being: using BoxSelect2d in a grid, box-select scrolling down while wiggling
    //   left and right: it affects coarse clipping + can emit multiple SetRange with 1 item each.
    // FIXME-OPT: For each block of consecutive SetRange request:
    // - add all requests to a sorted list, store ID, selected, offset in ImGuiStorage.
    // - rewrite sorted storage a single time.
    for (ImGuiSelectionRequest& req : ms_io->Requests)
    {
        if (req.Type == ImGuiSelectionRequestType_SetAll)
        {
            Clear();
            if (req.Selected)
            {
                _Storage.Data.reserve(ms_io->ItemsCount);
                const int size_before_amends = _Storage.Data.Size;
                for (int idx = 0; idx < ms_io->ItemsCount; idx++, _SelectionOrder++)
                    ImGuiSelectionBasicStorage_BatchSetItemSelected(this, GetStorageIdFromIndex(idx), req.Selected, size_before_amends, _SelectionOrder);
                ImGuiSelectionBasicStorage_BatchFinish(this, req.Selected, size_before_amends);
            }
        }
        else if (req.Type == ImGuiSelectionRequestType_SetRange)
        {
            const int selection_changes = (int)req.RangeLastItem - (int)req.RangeFirstItem + 1;
            //ImGuiContext& g = *GImGui; IMGUI_DEBUG_LOG_SELECTION("Req %d/%d: set %d to %d\n", ms_io->Requests.index_from_ptr(&req), ms_io->Requests.Size, selection_changes, req.Selected);
            if (selection_changes == 1 || (selection_changes < Size / 100))
            {
                // Multiple sorted insertion + copy likely to be faster.
                // Technically we could do a single copy with a little more work (sort sequential SetRange requests)
                for (int idx = (int)req.RangeFirstItem; idx <= (int)req.RangeLastItem; idx++)
                    SetItemSelected(GetStorageIdFromIndex(idx), req.Selected);
            }
            else
            {
                // Append insertion + single sort likely be faster.
                // Use req.RangeDirection to set order field so that Shift+Clicking from 1 to 5 is different than Shift+Clicking from 5 to 1
                const int size_before_amends = _Storage.Data.Size;
                int selection_order = _SelectionOrder + ((req.RangeDirection < 0) ? selection_changes - 1 : 0);
                for (int idx = (int)req.RangeFirstItem; idx <= (int)req.RangeLastItem; idx++, selection_order += req.RangeDirection)
                    ImGuiSelectionBasicStorage_BatchSetItemSelected(this, GetStorageIdFromIndex(idx), req.Selected, size_before_amends, selection_order);
                if (req.Selected)
                    _SelectionOrder += selection_changes;
                ImGuiSelectionBasicStorage_BatchFinish(this, req.Selected, size_before_amends);
            }
        }
    }
}