Add Button to FEM Toolbar Tutorial

In this tutorial we are going to add the Flow equation to FreeCAD and implement support for elmer solver. Please make sure you have read and understood Extend FEM Module before reading this tutorial.

The task can be split into five parts:
 * New equation type. This step must only be done if the equation doesn't exist in FreeCAD yet (as opposed to a equation that is already in FreeCAD but not supported by the target solver).

New Equation Type
In this step we are going to modify the following files: We also need to create an Icon file:
 * src/Mod/Fem/femcommands/commands.py
 * src/Mod/Fem/Gui/Workbench.cpp
 * src/Mod/Fem/Gui/Resources/Fem.qrc
 * src/Mod/Fem/Gui/Resources/icons/FEM_EquationFlow.svg

We need a FEM_EquationFlow.svg file and has to be put into. The new FEM_EquationFlow.svg icon has to be registered for the GUI-button with in  (in ).

In addition to those base classes we have to create a new command class that adds a flow equation to the selected solver object. Next, the command/equation has to be added to the module. Just copy an existing command and adjust the icon, menu text and tool-tip in __init__(self). Don't forget to register the command at the bottom of the module file by using the addCommand(...) method. Please see the discussion in the forum at https://forum.freecadweb.org/viewtopic.php?f=18&t=46693&start=10#p402004 if icons are involved. class _EquationFlow(CommandManager): "The FEM_EquationFlow command definition"

def __init__(self): super(_EquationFlow, self).__init__ self.menuetext = "Flow equation" self.tooltip = "Creates a FEM equation for flow" self.is_active = "with_solver_elmer" self.do_activated = "add_obj_on_gui_selobj_noset_edit" ... FreeCADGui.addCommand(   "FEM_EquationFlow",    _EquationFlow )

The FEM workbench has several toolbars and menus. We will add the new command on to both the solve toolbar and the solve menu.

To add it to the solve toolbar, search for the following code snippet in and add the new command to the rest of the equation commands. Gui::ToolBarItem* solve = new Gui::ToolBarItem(root); solve->setCommand("Solve"); *solve << "FEM_SolverCalculixCxxtools" << "FEM_SolverCalculiX" << "FEM_SolverElmer" << "Separator" << "FEM_EquationElasticity" << "FEM_EquationElectrostatic" +         << "FEM_EquationFlow" << "FEM_EquationFluxsolver" << "FEM_EquationElectricforce" << "FEM_EquationHeat" << "Separator" << "FEM_SolverControl" << "FEM_SolverRun";

To add the flow equation command to the solve menu of the FEM workbench, search for the following code snippet in. Gui::MenuItem* solve = new Gui::MenuItem; root->insertItem(item, solve); solve->setCommand("&Solve"); *solve << "FEM_SolverCalculixCxxtools" << "FEM_SolverCalculiX" << "FEM_SolverElmer" << "FEM_SolverZ88" << "Separator" << "FEM_EquationElasticity" << "FEM_EquationElectrostatic" +         << "FEM_EquationFlow" << "FEM_EquationFluxsolver" << "FEM_EquationElectricforce" << "FEM_EquationHeat" << "Separator" << "FEM_SolverControl" << "FEM_SolverRun";