GladeVCP: Glade Virtual Control Panel

Both support the creation of panels with HAL widgets - user interface elements like LED’s, buttons, sliders etc whose values are linked to a HAL pin, which in turn interfaces to the rest of LinuxCNC.

PyVCP:

GladeVCP:

While running configs/sim/axis/gladevcp_panel.ini or configs/sim/axis/gladevcp_tab.ini, explore Show HAL Configuration - you will find the gladevcp HAL component and may observe their pin values while interacting with the widgets in the panel. The HAL setup can be found in configs/axis/gladevcp/manual-example.hal.

The example panel has two frames at the bottom. The panel is configured so that resetting ESTOP activates the Settings frame and turning the machine on enables the Commands frame at the bottom. The HAL widgets in the Settings frame are linked to LEDs and labels in the Status frame, and to the current and prepared tool number - play with them to see the effect. Executing the T<toolnumber> and M6 commands in the MDI window will change the current and prepared tool number fields.

The buttons in the Commands frame are MDI Action widgets - pressing them will execute an MDI command in the interpreter. The third button Execute Oword subroutine is an advanced example - it takes several HAL pin values from the Settings frame, and passes them as parameters to the Oword subroutine. The actual parameters received by the routine are displayed by (DEBUG, ) commands - see ../../nc_files/oword.ngc for the subroutine body.

To see how the panel is integrated into AXIS, see the [DISPLAY]GLADEVCP statement in configs/sim/axis/gladevcp/gladevcp_panel.ini, the [DISPLAY]EMBED* statement in configs/sim/axis/gladevcp/gladevcp_tab.ini and [HAL]POSTGUI_HALFILE statements in both configs/sim/axis/gladevcp/gladevcp_tab.ini and configs/sim/axis/gladevcp/gladevcp_panel.ini.

The user interface is created with the Glade UI editor - to explore it, you need to have Glade installed. To edit the user interface, run the command

The required glade program may be named glade-gtk2 on more recent systems.

The center window shows the appearance of the UI. All user interface objects and support objects are found in the right top window, where you can select a specific widget (or by clicking on it in the center window). The properties of the selected widget are displayed, and can be changed, in the right bottom window.

To see how MDI commands are passed from the MDI Action widgets, explore the widgets listed under Actions in the top right window, and in the right bottom window, under the General tab, the MDI command property.

See how a Python callback is integrated into the example:

The is just touching upon the concept - the callback mechanism will be handled in more detail in the GladeVCP Programming section.

To view or modify Glade UI files, you need Glade 3.38.2 or later installed - it is not needed just to run a GladeVCP panel. If the glade command is missing, install it with the command:

Then verify installed version, which must be equal or superior to 3.6.7:

Glade contains an internal Python interpreter, and only Python 3 is supported. This is true for Debian Bullseye, Ubuntu 21 and Mint 21 or later. Older versions will not work, you will get a Python error.

This section just outlines the initial LinuxCNC-specific steps. For more information and a tutorial on Glade, see http://glade.gnome.org. Some Glade tips & tricks may also be found on YouTube.

Either modify an existing UI component by running glade <file>.ui or start a new one by just running the glade command from the shell.

This will look like this:

Glade tends to write a lot of messages to the shell window, which mostly can be ignored. Select File→Save as, give it a name like myui.ui and make sure it is saved as GtkBuilder file (radio button left bottom corner in Save dialog). GladeVCP will also process the older libglade format correctly but there is no point in using it. The convention for GtkBuilder file extension is .ui.

You’re now ready to give it a try (while LinuxCNC, e.g. AXIS is running) it with:

GladeVCP creates a HAL component named like the basename of the UI file - myui in this case - unless overridden by the -c <component name> option. If running AXIS, just try Show HAL configuration and inspect its pins.

You might wonder why widgets contained a HAL_Hbox or HAL_Table appear greyed out (inactive). HAL containers have an associated HAL pin which is off by default, which causes all contained widgets to render inactive. A common use case would be to associate these container HAL pins with halui.machine.is-on or one of the halui.mode signals, to assure some widgets appear active only in a certain state.

To just activate a container, execute the HAL command setp gladevcp.<container-name> 1.

The suggested way of linking HAL pins in a GladeVCP panel is to collect them in a separate file with extension .hal. This file is passed via the POSTGUI_HALFILE= option in the HAL section of your INI file.

Place the GladeVCP panel in the righthand side panel by specifying the following in the INI file:

The default HAL component name of a GladeVCP application started with the GLADEVCP option is: gladevcp.

The command line actually run by AXIS in the above configuration is as follows:

You may add arbitrary gladevcp options here, as long as they dont collide with the above command line options.

It is possible to create a custom HAL component name by adding the -c option:

The command line actually run by AXIS for the above is:

To do so, edit your INI file and add to the DISPLAY and HAL sections of INI file as follows:

Note the halcmd loadusr way of starting the tab command - this assures that POSTGUI_HALFILE will only be run after the HAL component is ready. In rare cases you might run a command here which uses a tab but does not have an associated HAL component. Such a command can be started without halcmd loadusr, and this signifies to AXIS that it does not have to wait for a HAL component since there is none.

When changing the component name in the above example, note that the names used in -Wn <component> and -c <component> must be identical.

Try it out by running AXIS - there should be a new tab called GladeVCP demo near the DRO tab. Select that tab, you should see the example panel nicely fit within AXIS.

To do add a GladeVCP tab to Touchy, edit your INI file as follows:

Note the following differences to the AXIS tab setup:

Most HAL widgets have a single associated HAL pin with the same HAL name as the widget (glade: General→Name).

Exceptions to this rule currently are:

HAL widgets are instances of GtKWidgets and hence inherit the methods, properties and signals of the applicable GtkWidget class. For instance, to figure out which GtkWidget-related methods, properties and signals a HAL_Button has, lookup the description of GtkButton in the PyGObject API Reference.

An easy way to find out the inheritance relationship of a given HAL widget is as follows: Run glade, place the widget in a window, and select it; then choose the Signals tab in the Properties window. For example, selecting a HAL_LED widget, this will show that a HAL_LED is derived from a GtkWidget, which in turn is derived from a GtkObject, and eventually a GObject.

Full class hierarchy can be seen by invoking the GtkInspector while in the Glade GUI by selecting a widget then pressing Control-Shift-I. If the Inspector doesn’t open then it can be enabled from a terminal by entering:

The Inspector is also handy for testing css style changes "on the fly" as well as determining all the properties and signals available for a widget.

HAL Widgets also have a few HAL-specific Python attributes:

The are several HAL-specific methods of HAL Widgets, but the only relevant method is:

As a general rule, if you need to set a HAL output widget’s value from Python code, do so by calling the underlying Gtk setter (e.g., set_active(), set_value()). Do not try to set the associated pin’s value by halcomp[pinname] = value directly because the widget will not take notice of the change!

It might be tempting to set HAL widget input pins programmatically. Note this defeats the purpose of an input pin in the first place - it should be linked to, and react to signals generated by other HAL components. While there is currently no write protection on writing to input pins in HAL Python, this doesn’t make sense. You might use setp _pinname_ _value_ in the associated HAL file for testing though.

It is perfectly OK to set an output HAL pin’s value with halcomp[pinname] = value provided this HAL pin is not associated with a widget, that is, has been created by the hal_glib.GPin(halcomp.newpin(<name>,<type>,<direction>)) method (see GladeVCP Programming for an example).

Event-driven programming means that the UI tells your code when "something happens" - through a callback, like when a button was pressed. The output HAL widgets (those which display a HAL pin’s value) like LED, Bar, VBar, Meter, etc., support the hal-pin-changed signal, which may cause a callback into your Python code when - well, a HAL pin changes its value. This means there’s no more need for permanent polling of HAL pin changes in your code, the widgets do that in the background and let you know.

Here is an example how to set a hal-pin-changed signal for a HAL_LED in the Glade UI editor:

The example in configs/apps/gladevcp/complex shows how this is handled in Python.

This group of widgets are derived from various Gtk buttons and consists of HAL_Button, HAL_ToggleButton, HAL_RadioButton and CheckButton widgets. All of them have a single output BIT pin named identical to the widget. Buttons have no additional properties compared to their base Gtk classes.

See configs/apps/gladevcp/by-widget/ for a GladeVCP applications and UI file for working with radio buttons.

HAL_HScale and HAL_VScale are derived from the GtkHScale and GtkVScale respectively.

To make a scale useful in Glade, add an Adjustment (General → Adjustment → New or existing adjustment) and edit the adjustment object. It defines the default/min/max/increment values. Also, set adjustment Page size and Page increment to zero to avoid warnings.

HAL SpinButton is derived from GtkSpinButton and holds two pins:

To be useful, Spinbuttons need an adjustment value like scales, see above.

The hal_dial widget simulates a jogwheel or adjustment dial.
It can be operated with the mouse. You can just use the mouse wheel, while the mouse cursor is over the Hal_Dial widget, or you hold the left mouse button and move the cursor in circular direction to increase or degrease the counts.
By double clicking the left or right button the scale factor can be increased or decreased.

The jogwheel widget simulates a real jogwheel. It can be operated with the mouse. You can just use the mouse wheel, while the mouse cursor is over the JogWheel widget, or you push the left mouse button and move the cursor in circular direction to increase or degrease the counts.

As moving the mouse the drag and drop way may be faster than the widget can update itself, you may loose counts turning to fast. It is recommended to use the mouse wheel, and only for very rough movements the drag and drop way.

speedcontrol is a widget specially made to control an adjustment with a touch screen. It is a replacement to the normal scale widget which is difficult to slide on a touch screen.

The value is controlled with two button to increase or decrease the value. The increment will change as long a button is pressed. The value of each increment as well as the time between two changes can be set using the widget properties.

hal_label is a simple widget based on GtkLabel which represents a HAL pin value in a user-defined format.

These containers are meant to be used to insensitize (grey out) or hide their children.
Insensitized children will not respond to input.

The hal_led simulates a real indicator LED.
It has a single input BIT pin which controls its state: ON or OFF.

HAL_ComboBox is derived from gtk.ComboBox. It enables choice of a value from a dropdown list.

HAL_Bar and HAL_VBar widgets for horizontal and vertical bars representing float values.

HAL_Meter is a widget similar to PyVCP meter - it represents a float value.

This widget is for plotting values over time.

Gremlin is a plot preview widget similar to the AXIS preview window. It assumes a running LinuxCNC environment like AXIS or Touchy. To connect to it, inspects the INI_FILE_NAME environment variable. Gremlin displays the current NGC file - it does monitor for changes and reloads the ngc file if the file name in AXIS/Touchy changes. If you run it in a GladeVCP application when LinuxCNC is not running, you might get a traceback because the Gremlin widget can’t find LinuxCNC status, like the current file name.

The HAL_Offset widget is used to display the offset of a single axis.

The DRO widget is used to display the current axis position.

The Combi_DRO widget is used to display the current, the relative axis position and the distance to go in one DRO.
By clicking on the DRO the Order of the DRO will toggle around.
In Relative Mode the actual coordinate system will be displayed.

This is a touch screen friendly widget to select a file and to change directories.

This is a simple calculator widget, that can be used for numerical input.
You can preset the display and retrieve the result or that preset value.

This is a tooleditor widget for displaying and modifying a tool file.
If in lathe mode, it will display wear offsets and tool offsets separately.
Wear offsets are designated by tool number above 10000 (Fanuc style).
It checks the current file once a second to see if LinuxCNC updated it.

The Offsetpage widget is used to display/edit the offsets of all the axes.
It has convenience buttons for zeroing G92 and Rotation-Around-Z offsets.
It will only allow you to select the edit mode when the machine is on and idle.
You can directly edit the offsets in the table at this time. Unselect the edit button to allow the OffsetPage to reflect changes.

This is for displaying and simple editing of G-code. It looks for .ngc highlighting specs in ~/share/gtksourceview-4/language-specs/. The current running line will be highlighted.

With external Python glue code it can:

This is for displaying and entering MDI codes.
It will be automatically grayed out when MDI is not available, e.g., during E-stop and program running.

For some applications it might be desirable to have a background image - like a functional diagram - and position widgets at appropriate places in that image. A good combination is setting a bitmap background image, like from a .png file, making the GladeVCP window fixed-size, and use the Glade Fixed widget to position widgets on this image. The code for the below example can be found in configs/apps/gladevcp/animated-backdrop:

VCP Action widgets are one-shot type widgets. They implement a single action and are for use in simple buttons, menu entries or radio/check groups.

This widget is used to execute small arbitrary Python code.

The command string may use special keywords to access important functions.

There are options to

Example command to just print a message to the terminal:

Example command to set the machine to off state:

Example command to call a handler function that passes data:

You can use a semicolon to separate multiple commands;

More information on INFO and ACTION can be found here: GladeVCP Libraries modules.

More information on GStat can be found here: GStat.

These are bi-modal widgets. They implement two actions or use a second (usually pressed) state to indicate that currently an action is running. Toggle actions are aimed for use in ToggleButtons, ToggleToolButtons or toggling menu items. A simplex example is the ESTOP toggle button.

Currently the following widgets are available:

The following toggle actions have only one associated command and use the pressed state to indicate that the requested operation is running:

These widgets provide a means to execute arbitrary MDI commands.
The Action_MDI widget does not wait for command completion as the Action_MDI Toggle does, which remains disabled until command complete.

configs/apps/gladevcp/mdi-command-example/whoareyou.ui is a Glade UI file which conveys the basics:

You’ll notice that the button associated with the Action_MDI action is grayed out if the machine is off, in E-Stop or if the interpreter is running. It will automatically become active when the machine is turned on and out of E-Stop, and the program is idle.

Optionally, MDI command strings may have parameters substituted before they are passed to the interpreter. Parameters currently may be names of HAL pins in the GladeVCP component. This is how it works:

The example UI file is configs/apps/gladevcp/mdi-command-example/speed.ui. Here’s what you get when running it:

It’s perfectly OK to call an O-word subroutine in an MDI command, and pass HAL pin values as actual parameters. An example UI file is in configs/apps/gladevcp/mdi-command-example/owordsub.ui.

Place nc_files/gladevcp_lib/oword.ngc so AXIS can find it, and run gladevcp owordsub.ui from a terminal window. This looks like so:

The LinuxCNC G-code interpreter has a single global set of variables, like feed, spindle speed, relative/absolute mode and others. If you use G-code commands or O-word subs, some of these variables might get changed by the command or subroutine - for example, a probing subroutine will very likely set the feed value quite low. With no further precautions, your previous feed setting will be overwritten by the probing subroutine’s value.

To deal with this surprising and undesirable side effect of a given O-word subroutine or G-code statement executed with an LinuxCNC ToggleAction_MDI, you might associate pre-MDI and post-MDI handlers with a given LinuxCNC ToggleAction_MDI. These handlers are optional and provide a way to save any state before executing the MDI Action, and to restore it to previous values afterwards. The signal names are mdi-command-start and mdi-command-stop; the handler names can be set in Glade like any other handler.

Here’s an example how a feed value might be saved and restored by such handlers (note that LinuxCNC command and status channels are available as self.linuxcnc and self.stat through the VCP_ActionBase class):

Only the Action_MDI Toggle widget supports these signals.

Many actions depend on LinuxCNC status - is it in manual, MDI or auto mode? Is a program running, paused or idle? You cannot start an MDI command while a G-code program is running, so this needs to be taken care of. Many LinuxCNC actions take care of this themselves, and related buttons and menu entries are deactivated when the operation is currently impossible.

When using Python event handlers - which are at a lower level than Actions - one needs to take care of dealing with status dependencies oneself. For this purpose, there’s the LinuxCNC Stat widget: to associate LinuxCNC status changes with event handlers.

LinuxCNC Stat has no visible component - you just add it to your UI with Glade. Once added, you can associate handlers with its following signals:

Most widget sets, and their associated user interface editors, support the concept of callbacks, i.e. functions in user-written code which are executed when something happens in the UI - events like mouse clicks, characters typed, mouse movement, timer events, window hiding and exposure and so forth.

HAL output widgets typically map input-type events like a button press to a value change of the associated HAL pin by means of such a - predefined - callback. Within PyVCP, this is really the only type of event handling supported - doing something more complex, like executing MDI commands to call a G-code subroutine, is not supported.

Within GladeVCP, HAL pin changes are just one type of the general class of events (called signals) in GTK+. Most widgets may originate such signals, and the Glade editor supports associating such a signal with a Python method or function name.

If you decide to use user-defined actions, your job is to write a Python module whose class methods - or in the simple case, just functions - can be referred to in Glade as event handlers. GladeVCP provides a way to import your module(s) at startup and will automatically link your event handlers with the widget signals as set in the Glade UI description.

There are three libraries of functions that can be used to help program GladeVCP.

Importing and instantiating the libraries:

Using the library functions:

More information can be found here: GladeVCP Libraries modules. There is a sample configuration that demonstrates using the core library with GladeVCP’s action Python widgets and with a Python handler file. Try loading sim/axis/gladevcp/gladevcp_panel_tester.

This is just a minimal example to convey the idea - details are laid out in the rest of this section.

GladeVCP can not only manipulate or display HAL pins, you can also write regular event handlers in Python. This could be used, among others, to execute MDI commands. Here’s how you do it:

Write a Python module like so and save as e.g. handlers.py:

In Glade, define a button or HAL button, select the Signals tab, and in the GtkButton properties select the pressed line. Enter on_button_press there, and save the Glade file.

Then add the option -u handlers.py to the GladeVCP command line. If your event handlers are spread over several files, just add multiple -u <pyfilename> options.

Now, pressing the button should change its label since it is set in the callback function.

What the +-u+ flag does: all Python functions in this file are collected and setup as potential callback handlers for your Gtk widgets - they can be referenced from Glade Signals tabs. The callback handlers are called with the particular object instance as parameter, like the GtkButton instance above, so you can apply any GtkButton method from there.

Or do some more useful stuff, like calling an MDI command!

HAL input widgets, like a LED, automatically associate their HAL pin state (on/off) with the optical appearance of the widget (LED lit/dark).

Beyond this built-in functionality, one may associate a change callback with any HAL pin, including those of predefined HAL widgets. This fits nicely with the event-driven structure of a typical widget application: Every activity, be it mouse click, key, timer expired, or the change of a HAL pin’s value, generates a callback and is handled by the same orthogonal mechanism.

For user-defined HAL pins not associated with a particular HAL widget, the signal name is value-changed. See the Adding HAL pins section below for details.

HAL widgets come with a pre-defined signal called hal-pin-changed. See the HAL Widgets section for details.

The overall approach is as follows:

It is important to know in which state of affairs your get_handlers() function is called so you know what is safe to do there and what not. First, modules are imported and initialized in command line order. After successful import, get_handlers() is called in the following state:

Once all modules have been imported and method names extracted, the following steps happen:

So when your handler class is initialized, all widgets are existent but not yet realized (displayed on screen). And the HAL component isn’t ready as well, so its unsafe to access pins values in your __init__() method.

If you want to have a callback to execute at program start after it is safe to access HAL pins, then a connect a handler to the realize signal of the top level window1 (which might be its only real purpose). At this point GladeVCP is done with all setup tasks, the HAL file has been run, and GladeVCP is about to enter the Gtk main loop.

Within a class, method names must be unique. However, it is OK to have multiple class instances passed to GladeVCP by get_handlers() with identically named methods. When the corresponding signal occurs, these methods will be called in definition order - module by module, and within a module, in the order class instances are returned by get_handlers().

Instead of extending GladeVCP for any conceivable option which could potentially be useful for a handler class, you may use the -U <useroption> flag (repeatedly if you wish). This flag collects a list of <useroption> strings. This list is passed to the get_handlers() function (useropts argument). Your code is free to interpret these strings as you see fit. An possible usage would be to pass them to the Python exec function in your get_handlers() as follows:

This way you can pass arbitrary Python statements to your module through the gladevcp -U option, for example:

This should set debug to 2 and confirm that your module actually did it.

An annoying aspect of GladeVCP in its earlier form and PyVCP is the fact that you may change values and HAL pins through text entry, sliders, spin boxes, toggle buttons, etc., but their settings are not saved and restored at the next run of LinuxCNC - they start at the default value as set in the panel or widget definition.

GladeVCP has an easy-to-use mechanism to save and restore the state of HAL widgets, and program variables (in fact any instance attribute of type int, float, bool or string).

This mechanism uses the popular INI file format to save and reload persistent attributes.

Imagine renaming, adding or deleting widgets in Glade: An .INI file lying around from a previous program version, or an entirely different user interface, would be not be able to restore the state properly since variables and types might have changed.

GladeVCP detects this situation by a signature which depends on all object names and types which are saved and to be restored. In the case of signature mismatch, a new INI file with default settings is generated.

If you want any of Gtk widget state, HAL widgets output pin’s values and/or class attributes of your handler class to be retained across invocations, proceed as follows:

Then associate an INI file with this descriptor:

After restore_state(), self will have attributes set if as running the following:

Note that types are saved and preserved on restore. This example assumes that the INI file didn’t exist or had the default values from self.defaults.

After this incantation, you can use the following IniFile methods:

To save the widget and/or variable state on exit, proceed as follows:

This will save state and shutdown GladeVCP properly, regardless whether the panel is embedded in AXIS, or a standalone window.

Next time you start the GladeVCP application, the widgets should come up in the state when the application was closed.

By default, the reaction of GladeVCP to a Ctrl-C event is to just exit - without saving state. To make sure that this case is covered, add a handler call on_unix_signal which will be automatically be called on Ctrl-C (actually on the SIGINT and SIGTERM signals). Example:

You can do that, but note that the values in self.defaults override your edits if there is a syntax or type error in your edit. The error is detected, a console message will hint about that happened, and the bad inifile will be renamed to have the .BAD suffix. Subsequent bad INI files overwrite earlier .BAD files.

If you need HAL pins which are not associated with a specific HAL widget, add them as follows:

To get a callback when this pin’s value changes, associate a value-change callback with this pin, add:

and define a callback method (or function, in this case leave out the self parameter):

Since GladeVCP uses Gtk widgets which rely on the PyGObject base class, the full GLib functionally is available. Here is an example for a timer callback:

With Glade, widget properties are typically set fixed while editing. You can, however, set widget properties at runtime, for instance from INI file values, which would typically be done in the handler initialization code. Setting properties from HAL pin values is possible, too.

In the following example (assuming a HAL Meter widget called meter), the meter’s min value is set from an INI file parameter at startup, and the max value is set via a HAL pin, which causes the widget’s scale to readjust dynamically:

GladeVCP uses the hal_glib library, which can be used to connect a "watcher" signal on a HAL input pin.
This signal can be used to register a function to call when the HAL pin changes state.

One must import the hal_glib and the hal modules:

Then make a pin and connect a value-changed (the watcher) signal to a function call:

And have a function to be called:

Visit linuxcnc_root_directory/configs/apps/gladevcp for running examples and starters for your own projects.