Method FindBestWindowPosForPopupEx

include/imgui/imgui.cpp:12696–12768

r_avoid = the rectangle to avoid (e.g. for tooltip it is a rectangle around the mouse cursor which we want to avoid. for popups it's a small point around the cursor.) r_outer = the visible area rectangle, minus safe area padding. If our popup size won't fit because of safe area padding we ignore it. (r_outer is usually equivalent to the viewport rectangle minus padding, but when multi-viewports ar

//  information are available, it may represent the entire platform monitor from the frame of reference of the current viewport.
//  this allows us to have tooltips/popups displayed out of the parent viewport.)
ImVec2 ImGui::FindBestWindowPosForPopupEx(const ImVec2& ref_pos, const ImVec2& size, ImGuiDir* last_dir, const ImRect& r_outer, const ImRect& r_avoid, ImGuiPopupPositionPolicy policy)
{
    ImVec2 base_pos_clamped = ImClamp(ref_pos, r_outer.Min, r_outer.Max - size);
    //GetForegroundDrawList()->AddRect(r_avoid.Min, r_avoid.Max, IM_COL32(255,0,0,255));
    //GetForegroundDrawList()->AddRect(r_outer.Min, r_outer.Max, IM_COL32(0,255,0,255));

    // Combo Box policy (we want a connecting edge)
    if (policy == ImGuiPopupPositionPolicy_ComboBox)
    {
        const ImGuiDir dir_preferred_order[ImGuiDir_COUNT] = { ImGuiDir_Down, ImGuiDir_Right, ImGuiDir_Left, ImGuiDir_Up };
        for (int n = (*last_dir != ImGuiDir_None) ? -1 : 0; n < ImGuiDir_COUNT; n++)
        {
            const ImGuiDir dir = (n == -1) ? *last_dir : dir_preferred_order[n];
            if (n != -1 && dir == *last_dir) // Already tried this direction?
                continue;
            ImVec2 pos;
            if (dir == ImGuiDir_Down)  pos = ImVec2(r_avoid.Min.x, r_avoid.Max.y);          // Below, Toward Right (default)
            if (dir == ImGuiDir_Right) pos = ImVec2(r_avoid.Min.x, r_avoid.Min.y - size.y); // Above, Toward Right
            if (dir == ImGuiDir_Left)  pos = ImVec2(r_avoid.Max.x - size.x, r_avoid.Max.y); // Below, Toward Left
            if (dir == ImGuiDir_Up)    pos = ImVec2(r_avoid.Max.x - size.x, r_avoid.Min.y - size.y); // Above, Toward Left
            if (!r_outer.Contains(ImRect(pos, pos + size)))
                continue;
            *last_dir = dir;
            return pos;
        }
    }

    // Tooltip and Default popup policy
    // (Always first try the direction we used on the last frame, if any)
    if (policy == ImGuiPopupPositionPolicy_Tooltip || policy == ImGuiPopupPositionPolicy_Default)
    {
        const ImGuiDir dir_preferred_order[ImGuiDir_COUNT] = { ImGuiDir_Right, ImGuiDir_Down, ImGuiDir_Up, ImGuiDir_Left };
        for (int n = (*last_dir != ImGuiDir_None) ? -1 : 0; n < ImGuiDir_COUNT; n++)
        {
            const ImGuiDir dir = (n == -1) ? *last_dir : dir_preferred_order[n];
            if (n != -1 && dir == *last_dir) // Already tried this direction?
                continue;

            const float avail_w = (dir == ImGuiDir_Left ? r_avoid.Min.x : r_outer.Max.x) - (dir == ImGuiDir_Right ? r_avoid.Max.x : r_outer.Min.x);
            const float avail_h = (dir == ImGuiDir_Up ? r_avoid.Min.y : r_outer.Max.y) - (dir == ImGuiDir_Down ? r_avoid.Max.y : r_outer.Min.y);

            // If there's not enough room on one axis, there's no point in positioning on a side on this axis (e.g. when not enough width, use a top/bottom position to maximize available width)
            if (avail_w < size.x && (dir == ImGuiDir_Left || dir == ImGuiDir_Right))
                continue;
            if (avail_h < size.y && (dir == ImGuiDir_Up || dir == ImGuiDir_Down))
                continue;

            ImVec2 pos;
            pos.x = (dir == ImGuiDir_Left) ? r_avoid.Min.x - size.x : (dir == ImGuiDir_Right) ? r_avoid.Max.x : base_pos_clamped.x;
            pos.y = (dir == ImGuiDir_Up) ? r_avoid.Min.y - size.y : (dir == ImGuiDir_Down) ? r_avoid.Max.y : base_pos_clamped.y;

            // Clamp top-left corner of popup
            pos.x = ImMax(pos.x, r_outer.Min.x);
            pos.y = ImMax(pos.y, r_outer.Min.y);

            *last_dir = dir;
            return pos;
        }