Method DockNodeCalcDropRectsAndTestMousePos

imgui_tiny_app/imgui/imgui.cpp:19830–19880

Retrieve the drop rectangles for a given direction or for the center + perform hit testing.

// Retrieve the drop rectangles for a given direction or for the center + perform hit testing.
bool ImGui::DockNodeCalcDropRectsAndTestMousePos(const ImRect& parent, ImGuiDir dir, ImRect& out_r, bool outer_docking, ImVec2* test_mouse_pos)
{
    ImGuiContext& g = *GImGui;

    const float parent_smaller_axis = ImMin(parent.GetWidth(), parent.GetHeight());
    const float hs_for_central_nodes = ImMin(g.FontSize * 1.5f, ImMax(g.FontSize * 0.5f, parent_smaller_axis / 8.0f));
    float hs_w; // Half-size, longer axis
    float hs_h; // Half-size, smaller axis
    ImVec2 off; // Distance from edge or center
    if (outer_docking)
    {
        //hs_w = ImTrunc(ImClamp(parent_smaller_axis - hs_for_central_nodes * 4.0f, g.FontSize * 0.5f, g.FontSize * 8.0f));
        //hs_h = ImTrunc(hs_w * 0.15f);
        //off = ImVec2(ImTrunc(parent.GetWidth() * 0.5f - GetFrameHeightWithSpacing() * 1.4f - hs_h), ImTrunc(parent.GetHeight() * 0.5f - GetFrameHeightWithSpacing() * 1.4f - hs_h));
        hs_w = ImTrunc(hs_for_central_nodes * 1.50f);
        hs_h = ImTrunc(hs_for_central_nodes * 0.80f);
        off = ImTrunc(ImVec2(parent.GetWidth() * 0.5f - hs_h, parent.GetHeight() * 0.5f - hs_h));
    }
    else
    {
        hs_w = ImTrunc(hs_for_central_nodes);
        hs_h = ImTrunc(hs_for_central_nodes * 0.90f);
        off = ImTrunc(ImVec2(hs_w * 2.40f, hs_w * 2.40f));
    }

    ImVec2 c = ImTrunc(parent.GetCenter());
    if      (dir == ImGuiDir_None)  { out_r = ImRect(c.x - hs_w, c.y - hs_w,         c.x + hs_w, c.y + hs_w);         }
    else if (dir == ImGuiDir_Up)    { out_r = ImRect(c.x - hs_w, c.y - off.y - hs_h, c.x + hs_w, c.y - off.y + hs_h); }
    else if (dir == ImGuiDir_Down)  { out_r = ImRect(c.x - hs_w, c.y + off.y - hs_h, c.x + hs_w, c.y + off.y + hs_h); }
    else if (dir == ImGuiDir_Left)  { out_r = ImRect(c.x - off.x - hs_h, c.y - hs_w, c.x - off.x + hs_h, c.y + hs_w); }
    else if (dir == ImGuiDir_Right) { out_r = ImRect(c.x + off.x - hs_h, c.y - hs_w, c.x + off.x + hs_h, c.y + hs_w); }

    if (test_mouse_pos == NULL)
        return false;

    ImRect hit_r = out_r;
    if (!outer_docking)
    {
        // Custom hit testing for the 5-way selection, designed to reduce flickering when moving diagonally between sides
        hit_r.Expand(ImTrunc(hs_w * 0.30f));
        ImVec2 mouse_delta = (*test_mouse_pos - c);
        float mouse_delta_len2 = ImLengthSqr(mouse_delta);
        float r_threshold_center = hs_w * 1.4f;
        float r_threshold_sides = hs_w * (1.4f + 1.2f);
        if (mouse_delta_len2 < r_threshold_center * r_threshold_center)
            return (dir == ImGuiDir_None);
        if (mouse_delta_len2 < r_threshold_sides * r_threshold_sides)
            return (dir == ImGetDirQuadrantFromDelta(mouse_delta.x, mouse_delta.y));
    }
    return hit_r.Contains(*test_mouse_pos);
}

// host_node may be NULL if the window doesn't have a DockNode already.
// FIXME-DOCK: This is misnamed since it's also doing the filtering.