Method ColorPicker4

3rdparty/imgui/src/imgui_widgets.cpp:6070–6437

Note: ColorPicker4() only accesses 3 floats if ImGuiColorEditFlags_NoAlpha flag is set. (In C++ the 'float col[4]' notation for a function argument is equivalent to 'float* col', we only specify a size to facilitate understanding of the code.) FIXME: we adjust the big color square height based on item width, which may cause a flickering feedback loop (if automatic height makes a vertical scrollbar

// FIXME: we adjust the big color square height based on item width, which may cause a flickering feedback loop (if automatic height makes a vertical scrollbar appears, affecting automatic width..)
// FIXME: this is trying to be aware of style.Alpha but not fully correct. Also, the color wheel will have overlapping glitches with (style.Alpha < 1.0)
bool ImGui::ColorPicker4(const char* label, float col[4], ImGuiColorEditFlags flags, const float* ref_col)
{
    ImGuiContext& g = *GImGui;
    ImGuiWindow* window = GetCurrentWindow();
    if (window->SkipItems)
        return false;

    ImDrawList* draw_list = window->DrawList;
    ImGuiStyle& style = g.Style;
    ImGuiIO& io = g.IO;

    const float width = CalcItemWidth();
    const bool is_readonly = ((g.NextItemData.ItemFlags | g.CurrentItemFlags) & ImGuiItemFlags_ReadOnly) != 0;
    g.NextItemData.ClearFlags();

    PushID(label);
    const bool set_current_color_edit_id = (g.ColorEditCurrentID == 0);
    if (set_current_color_edit_id)
        g.ColorEditCurrentID = window->IDStack.back();
    BeginGroup();

    if (!(flags & ImGuiColorEditFlags_NoSidePreview))
        flags |= ImGuiColorEditFlags_NoSmallPreview;

    // Context menu: display and store options.
    if (!(flags & ImGuiColorEditFlags_NoOptions))
        ColorPickerOptionsPopup(col, flags);

    // Read stored options
    if (!(flags & ImGuiColorEditFlags_PickerMask_))
        flags |= ((g.ColorEditOptions & ImGuiColorEditFlags_PickerMask_) ? g.ColorEditOptions : ImGuiColorEditFlags_DefaultOptions_) & ImGuiColorEditFlags_PickerMask_;
    if (!(flags & ImGuiColorEditFlags_InputMask_))
        flags |= ((g.ColorEditOptions & ImGuiColorEditFlags_InputMask_) ? g.ColorEditOptions : ImGuiColorEditFlags_DefaultOptions_) & ImGuiColorEditFlags_InputMask_;
    IM_ASSERT(ImIsPowerOfTwo(flags & ImGuiColorEditFlags_PickerMask_)); // Check that only 1 is selected
    IM_ASSERT(ImIsPowerOfTwo(flags & ImGuiColorEditFlags_InputMask_));  // Check that only 1 is selected
    if (!(flags & ImGuiColorEditFlags_NoOptions))
        flags |= (g.ColorEditOptions & ImGuiColorEditFlags_AlphaBar);

    // Setup
    int components = (flags & ImGuiColorEditFlags_NoAlpha) ? 3 : 4;
    bool alpha_bar = (flags & ImGuiColorEditFlags_AlphaBar) && !(flags & ImGuiColorEditFlags_NoAlpha);
    ImVec2 picker_pos = window->DC.CursorPos;
    float square_sz = GetFrameHeight();
    float bars_width = square_sz; // Arbitrary smallish width of Hue/Alpha picking bars
    float sv_picker_size = ImMax(bars_width * 1, width - (alpha_bar ? 2 : 1) * (bars_width + style.ItemInnerSpacing.x)); // Saturation/Value picking box
    float bar0_pos_x = picker_pos.x + sv_picker_size + style.ItemInnerSpacing.x;
    float bar1_pos_x = bar0_pos_x + bars_width + style.ItemInnerSpacing.x;
    float bars_triangles_half_sz = IM_TRUNC(bars_width * 0.20f);

    float backup_initial_col[4];
    memcpy(backup_initial_col, col, components * sizeof(float));

    float wheel_thickness = sv_picker_size * 0.08f;
    float wheel_r_outer = sv_picker_size * 0.50f;
    float wheel_r_inner = wheel_r_outer - wheel_thickness;
    ImVec2 wheel_center(picker_pos.x + (sv_picker_size + bars_width)*0.5f, picker_pos.y + sv_picker_size * 0.5f);

    // Note: the triangle is displayed rotated with triangle_pa pointing to Hue, but most coordinates stays unrotated for logic.