Method Step

plugins/Cardinal/src/DearImGui/imgui.cpp:2428–2552

}

bool ImGuiListClipper::Step()
{
    ImGuiContext& g = *GImGui;
    ImGuiWindow* window = g.CurrentWindow;
    ImGuiListClipperData* data = (ImGuiListClipperData*)TempData;

    ImGuiTable* table = g.CurrentTable;
    if (table && table->IsInsideRow)
        ImGui::TableEndRow(table);

    // No items
    if (ItemsCount == 0 || GetSkipItemForListClipping())
        return (void)End(), false;

    // While we are in frozen row state, keep displaying items one by one, unclipped
    // FIXME: Could be stored as a table-agnostic state.
    if (data->StepNo == 0 && table != NULL && !table->IsUnfrozenRows)
    {
        DisplayStart = data->ItemsFrozen;
        DisplayEnd = data->ItemsFrozen + 1;
        if (DisplayStart >= ItemsCount)
            return (void)End(), false;
        data->ItemsFrozen++;
        return true;
    }

    // Step 0: Let you process the first element (regardless of it being visible or not, so we can measure the element height)
    bool calc_clipping = false;
    if (data->StepNo == 0)
    {
        StartPosY = window->DC.CursorPos.y;
        if (ItemsHeight <= 0.0f)
        {
            // Submit the first item (or range) so we can measure its height (generally the first range is 0..1)
            data->Ranges.push_front(ImGuiListClipperRange::FromIndices(data->ItemsFrozen, data->ItemsFrozen + 1));
            DisplayStart = ImMax(data->Ranges[0].Min, data->ItemsFrozen);
            DisplayEnd = ImMin(data->Ranges[0].Max, ItemsCount);
            if (DisplayStart == DisplayEnd)
                return (void)End(), false;
            data->StepNo = 1;
            return true;
        }
        calc_clipping = true;   // If on the first step with known item height, calculate clipping.
    }

    // Step 1: Let the clipper infer height from first range
    if (ItemsHeight <= 0.0f)
    {
        IM_ASSERT(data->StepNo == 1);
        if (table)
            IM_ASSERT(table->RowPosY1 == StartPosY && table->RowPosY2 == window->DC.CursorPos.y);

        ItemsHeight = (window->DC.CursorPos.y - StartPosY) / (float)(DisplayEnd - DisplayStart);
        bool affected_by_floating_point_precision = ImIsFloatAboveGuaranteedIntegerPrecision(StartPosY) || ImIsFloatAboveGuaranteedIntegerPrecision(window->DC.CursorPos.y);
        if (affected_by_floating_point_precision)
            ItemsHeight = window->DC.PrevLineSize.y + g.Style.ItemSpacing.y; // FIXME: Technically wouldn't allow multi-line entries.

        IM_ASSERT(ItemsHeight > 0.0f && "Unable to calculate item height! First item hasn't moved the cursor vertically!");