Method TableHeader

ImGUI GLFW Tutorial/imgui/imgui_tables.cpp:2837–2974

Emit a column header (text + optional sort order) We cpu-clip text here so that all columns headers can be merged into a same draw call. Note that because of how we cpu-clip and display sorting indicators, you _cannot_ use SameLine() after a TableHeader()

// We cpu-clip text here so that all columns headers can be merged into a same draw call.
// Note that because of how we cpu-clip and display sorting indicators, you _cannot_ use SameLine() after a TableHeader()
void ImGui::TableHeader(const char* label)
{
    ImGuiContext& g = *GImGui;
    ImGuiWindow* window = g.CurrentWindow;
    if (window->SkipItems)
        return;

    ImGuiTable* table = g.CurrentTable;
    IM_ASSERT(table != NULL && "Need to call TableHeader() after BeginTable()!");
    IM_ASSERT(table->CurrentColumn != -1);
    const int column_n = table->CurrentColumn;
    ImGuiTableColumn* column = &table->Columns[column_n];

    // Label
    if (label == NULL)
        label = "";
    const char* label_end = FindRenderedTextEnd(label);
    ImVec2 label_size = CalcTextSize(label, label_end, true);
    ImVec2 label_pos = window->DC.CursorPos;

    // If we already got a row height, there's use that.
    // FIXME-TABLE: Padding problem if the correct outer-padding CellBgRect strays off our ClipRect?
    ImRect cell_r = TableGetCellBgRect(table, column_n);
    float label_height = ImMax(label_size.y, table->RowMinHeight - table->CellPaddingY * 2.0f);

    // Calculate ideal size for sort order arrow
    float w_arrow = 0.0f;
    float w_sort_text = 0.0f;
    char sort_order_suf[4] = "";
    const float ARROW_SCALE = 0.65f;
    if ((table->Flags & ImGuiTableFlags_Sortable) && !(column->Flags & ImGuiTableColumnFlags_NoSort))
    {
        w_arrow = ImFloor(g.FontSize * ARROW_SCALE + g.Style.FramePadding.x);
        if (column->SortOrder > 0)
        {
            ImFormatString(sort_order_suf, IM_ARRAYSIZE(sort_order_suf), "%d", column->SortOrder + 1);
            w_sort_text = g.Style.ItemInnerSpacing.x + CalcTextSize(sort_order_suf).x;
        }
    }

    // We feed our unclipped width to the column without writing on CursorMaxPos, so that column is still considering for merging.
    float max_pos_x = label_pos.x + label_size.x + w_sort_text + w_arrow;
    column->ContentMaxXHeadersUsed = ImMax(column->ContentMaxXHeadersUsed, column->WorkMaxX);
    column->ContentMaxXHeadersIdeal = ImMax(column->ContentMaxXHeadersIdeal, max_pos_x);

    // Keep header highlighted when context menu is open.
    const bool selected = (table->IsContextPopupOpen && table->ContextPopupColumn == column_n && table->InstanceInteracted == table->InstanceCurrent);
    ImGuiID id = window->GetID(label);
    ImRect bb(cell_r.Min.x, cell_r.Min.y, cell_r.Max.x, ImMax(cell_r.Max.y, cell_r.Min.y + label_height + g.Style.CellPadding.y * 2.0f));
    ItemSize(ImVec2(0.0f, label_height)); // Don't declare unclipped width, it'll be fed ContentMaxPosHeadersIdeal
    if (!ItemAdd(bb, id))
        return;

    //GetForegroundDrawList()->AddRect(cell_r.Min, cell_r.Max, IM_COL32(255, 0, 0, 255)); // [DEBUG]
    //GetForegroundDrawList()->AddRect(bb.Min, bb.Max, IM_COL32(255, 0, 0, 255)); // [DEBUG]

    // Using AllowItemOverlap mode because we cover the whole cell, and we want user to be able to submit subsequent items.
    bool hovered, held;