procedure TformMain.ImageEnView1MouseDown(Sender: TObject; Button: TMouseButton; Shift: TShiftState; X, Y: Integer);
begin
  var ThisLayer := ImageEnView1.FindLayerAt(X, Y);

  if Button = mbLeft then
  begin
    // ...
  end
  else if Button = mbRight then
  begin
    if ThisLayer > 0 then
      ImageEnView1.PopupMenus := [ievLayerEditing, ievLayerSelection]
    else if ThisLayer = 0 then 
      ImageEnView1.PopupMenus := [ievViewing, ievEditing, ievSelection];
  end;
end;

procedure TformMain.ImageEnView1MouseDown(Sender: TObject; Button: TMouseButton; Shift: TShiftState; X, Y: Integer);
begin
  var ThisLayer := ImageEnView1.FindLayerAt(X, Y);

  if Button = mbLeft then
  begin
    ImageEnView1.AutoToolbars := [];
    // ...
  end
  else if Button = mbRight then
  begin	
    if ThisLayer > 0 then // right-clicked a floating Layer (not the Background)
    begin
      // only CTRL modifier key pressed:
      if (GetKeyState(VK_CONTROL) < 0) and (GetKeyState(VK_SHIFT) >= 0) and (GetKeyState(VK_MENU) >= 0) then
      begin
        ImageEnView1.PopupMenus := [];
        ImageEnView1.AutoToolbars := [ievLayerEditing, ievLayerSelection];
      end
      // NO modifier key pressed:
      else if (GetKeyState(VK_CONTROL) >= 0) and (GetKeyState(VK_SHIFT) >= 0) and (GetKeyState(VK_MENU) >= 0) then
      begin
        ImageEnView1.PopupMenus := [ievLayerEditing, ievLayerSelection];
        ImageEnView1.AutoToolbars := [];
      end
    end
    else if ThisLayer = 0 then // right-clicked the Background Image
    begin
      ImageEnView1.PopupMenus := [ievViewing, ievEditing, ievSelection];
      ImageEnView1.AutoToolbars := [];
    end;
  end;	
end;

procedure TformMain.IEGlobalSettings1AddPopupMenuItem(Sender: TObject; ToolbarID, ButtonID: Integer; var Include: Boolean);
begin
  if ToolbarID = Layer_Selection_PopupMenu_ID  then
  begin
    if ButtonID = IELayersMergeToBackground_Button_ID then
      Include := True;
  end;
end;

procedure TformMain.FormCreate(Sender: TObject);
begin
  // layer-Popupmenu:
  IEGlobalSettings().LayerSelectionPopupMenu := [
    ivbLayersPropsDlg,   // TImageEnViewLayersShowPropertiesDialog
    ivbLayersGroup,      // TImageEnViewLayersGroup, TImageEnViewLayersUngroup
    ivbLayersOther,      // IELayerFlipHorz_Button_ID, IELayerFlipVert_Button_ID
    ivbLayersStyle,      // TIELayerFill, TIELayerBorder, TIELayerBorderWidth
    ivbLayersSize,       // TIELayerRestoreAspectRatio, TIELayerSizeToFit, TIEImageLayerRestoreSize
    //ivbLayersProps,
    //ivbLayersEdit,
    ivbLayersEditCurrent // TImageEnViewLayersMergeToBackground, TImageEnViewLayersRemoveCurrent,
                         // TImageEnViewLayersCropBackground, TIELayerConvertToImageLayer
  ];