Method Step

ImGUI GLFW Tutorial/imgui/imgui.cpp:2313–2414

}

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

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

    // No items
    if (ItemsCount == 0 || GetSkipItemForListClipping())
    {
        End();
        return false;
    }

    // Step 0: Let you process the first element (regardless of it being visible or not, so we can measure the element height)
    if (StepNo == 0)
    {
        // While we are in frozen row state, keep displaying items one by one, unclipped
        // FIXME: Could be stored as a table-agnostic state.
        if (table != NULL && !table->IsUnfrozenRows)
        {
            DisplayStart = ItemsFrozen;
            DisplayEnd = ItemsFrozen + 1;
            ItemsFrozen++;
            return true;
        }

        StartPosY = window->DC.CursorPos.y;
        if (ItemsHeight <= 0.0f)
        {
            // Submit the first item so we can measure its height (generally it is 0..1)
            DisplayStart = ItemsFrozen;
            DisplayEnd = ItemsFrozen + 1;
            StepNo = 1;
            return true;
        }

        // Already has item height (given by user in Begin): skip to calculating step
        DisplayStart = DisplayEnd;
        StepNo = 2;
    }

    // Step 1: the clipper infer height from first element
    if (StepNo == 1)
    {
        IM_ASSERT(ItemsHeight <= 0.0f);
        if (table)
        {
            const float pos_y1 = table->RowPosY1;   // Using this instead of StartPosY to handle clipper straddling the frozen row
            const float pos_y2 = table->RowPosY2;   // Using this instead of CursorPos.y to take account of tallest cell.
            ItemsHeight = pos_y2 - pos_y1;
            window->DC.CursorPos.y = pos_y2;
        }
        else
        {
            ItemsHeight = window->DC.CursorPos.y - StartPosY;