Method SplitterBehavior

include/imgui/imgui_widgets.cpp:1802–1858

Using 'hover_visibility_delay' allows us to hide the highlight and mouse cursor for a short time, which can be convenient to reduce visual noise.

// Using 'hover_visibility_delay' allows us to hide the highlight and mouse cursor for a short time, which can be convenient to reduce visual noise.
bool ImGui::SplitterBehavior(const ImRect& bb, ImGuiID id, ImGuiAxis axis, float* size1, float* size2, float min_size1, float min_size2, float hover_extend, float hover_visibility_delay, ImU32 bg_col)
{
    ImGuiContext& g = *GImGui;
    ImGuiWindow* window = g.CurrentWindow;

    if (!ItemAdd(bb, id, NULL, ImGuiItemFlags_NoNav))
        return false;

    // FIXME: AFAIK the only leftover reason for passing ImGuiButtonFlags_AllowOverlap here is
    // to allow caller of SplitterBehavior() to call SetItemAllowOverlap() after the item.
    // Nowadays we would instead want to use SetNextItemAllowOverlap() before the item.
    ImGuiButtonFlags button_flags = ImGuiButtonFlags_FlattenChildren;
#ifndef IMGUI_DISABLE_OBSOLETE_FUNCTIONS
    button_flags |= ImGuiButtonFlags_AllowOverlap;
#endif

    bool hovered, held;
    ImRect bb_interact = bb;
    bb_interact.Expand(axis == ImGuiAxis_Y ? ImVec2(0.0f, hover_extend) : ImVec2(hover_extend, 0.0f));
    ButtonBehavior(bb_interact, id, &hovered, &held, button_flags);
    if (hovered)
        g.LastItemData.StatusFlags |= ImGuiItemStatusFlags_HoveredRect; // for IsItemHovered(), because bb_interact is larger than bb

    if (held || (hovered && g.HoveredIdPreviousFrame == id && g.HoveredIdTimer >= hover_visibility_delay))
        SetMouseCursor(axis == ImGuiAxis_Y ? ImGuiMouseCursor_ResizeNS : ImGuiMouseCursor_ResizeEW);

    ImRect bb_render = bb;
    if (held)
    {
        float mouse_delta = (g.IO.MousePos - g.ActiveIdClickOffset - bb_interact.Min)[axis];

        // Minimum pane size
        float size_1_maximum_delta = ImMax(0.0f, *size1 - min_size1);
        float size_2_maximum_delta = ImMax(0.0f, *size2 - min_size2);
        if (mouse_delta < -size_1_maximum_delta)
            mouse_delta = -size_1_maximum_delta;
        if (mouse_delta > size_2_maximum_delta)
            mouse_delta = size_2_maximum_delta;

        // Apply resize
        if (mouse_delta != 0.0f)
        {
            *size1 = ImMax(*size1 + mouse_delta, min_size1);
            *size2 = ImMax(*size2 - mouse_delta, min_size2);
            bb_render.Translate((axis == ImGuiAxis_X) ? ImVec2(mouse_delta, 0.0f) : ImVec2(0.0f, mouse_delta));
            MarkItemEdited(id);
        }
    }

    // Render at new position
    if (bg_col & IM_COL32_A_MASK)
        window->DrawList->AddRectFilled(bb_render.Min, bb_render.Max, bg_col, 0.0f);
    const ImU32 col = GetColorU32(held ? ImGuiCol_SeparatorActive : (hovered && g.HoveredIdTimer >= hover_visibility_delay) ? ImGuiCol_SeparatorHovered : ImGuiCol_Separator);
    window->DrawList->AddRectFilled(bb_render.Min, bb_render.Max, col, 0.0f);

    return held;
}