Supported Tags

Tags are freeform text strings that appear in the tags field on Meta objects. This page lists the currently supported tags, and how they are used.

Widget Tag

A widget tag can be used to tell a GUI which widget to use to display an Attribute. It is created by calling the tag() method on a Widget enum member, like Widget.TEXTINPUT.tag() as introduced in the Counter Tutorial. It produces one of the following tags:

Tag	Description
widget:textinput	Editable text input box
widget:textupdate	Read only text update
widget:multilinetextupdate	Multi line text update
widget:led	On/Off LED indicator
widget:combo	Select from a number of choice values
widget:icon	This field gives the SVG icon for the whole Block
widget:help	Gives a URL for the help documentation for the Block
widget:group	Expandable section that other Attributes can appear in
widget:table	Table of rows with a widget type for each column
widget:checkbox	A box that can be checked or not
widget:flowgraph	Boxes with lines for child block connections
widget:tree	A nested tree of object models editor
widget:plot	A waveform plot
widget:meter	Progress meter

Linked Value Tag

A Linked Value tag can be attached to an Attribute to tell the GUI that there is another Attribute that can be monitored that should be displayed under the current Attribute with the text “Linked Value”. This is typically used for inports whose connected outport tag contain a current value that could be displayed. It is the responsibility of the Controller to change these tags if the path to the Attribute that is to be displayed changes.

These are created using the linked_value_tag.

Badge Value Tag

A Badge Value tag can be attached to a Port Attribute to tell the GUI that there is another Attribute that can be monitored that should be displayed as a badge for this Port. This is used on PandA to display the additional delay that can be added for sink ports.

These are created using the badge_value_tag.

Port Tag

The layout Attribute of a ManagerController is viewed with a FlowGraph widget. This widget allows the child Blocks declared in the layout to have a number of sourcePorts and sinkPorts which can be used to visualize the connections between Blocks. The sourcePort Attribute tag contains the value that a corresponding sinkPort should be set to when the ports are connected. The sinkPort tag contains the value that the sinkPort should be set to when disconnected.

Port types

The following port types are defined:

Type	Description
bool	Boolean value. Typically used in PandA
int32	32-bit signed integer. Typically used in PandA
NDArray	areaDetector NDArray port
motor	Motor record connection to CS or controller
block	Malcolm level connection to another Block

Source Port Tag

These are created on the child Attribute using the source_port_tag() method on the Port type enum member. The tag is sourcePort:<type>:<connected_value> where connected_value is the value that a sinkPort should be set to when they are connected. For instance, a PandA CLOCKS Block with an Attribute A that represents a produced clock would use Port.BOOL.source_port_tag("CLOCKS.A") to create a tag sourcePort:bool:CLOCKS.A

Sink Port Tag

These are created on the child Attribute using the sink_port_tag() method on the Port type enum member. The tag is sinkPort:<type>:<disconnected_value> where disconnected_value is the value that the sinkPorts should be set to when disconnected from a sourcePort. For instance, a PandA PULSE Block with an Attribute INP that represents where it should get its input pulse train from would use Port.BOOL.sink_port_tag("ZERO") to create a tag sinkPort:bool:ZERO

Group Tag

The widget:group tag on an Attribute creates a group expander area in the GUI that other Attributes can appear in. They signify this by using the group_tag function to create a group:<group_attribute_name> tag where group_attribute_name is the name of the Attribute with the widget:group tag on it. For instance if the outputs Attribute has a widget:group tag on it, other Attributes could appear in the outputs group expander by adding a group:outputs tag.

Config Tag

A config tag on an Attribute marks a field as one that should be saved and loaded by a parent ManagerController. These are created by using the config_tag function to create a config:<iteration> tag where iteration is a positive number. Loading of attributes takes place in a number of iterations, starting with the lowest number, with all Attributes in a single iteration being set simultaneously.

Method Return Unpacked Tag

A method:return:unpacked tag is created using the method_return_unpacked function. Its purpose is defined in the docstring:

malcolm.core.method_return_unpacked()

This method has a single element returns, and when called will return this single element unpacked rather than in a single element map

E.g.

hello.greet(“me”) -> “Hello me” not {“return”: “Hello me”}

Version Tag

A version:pymalcolm:<version> tag is created and attached to every Block so that clients know the version of pymalcolm that is hosting the Block.

Hidden Method Tag

All Methods are displayed in the GUI by default. To hide a method, add a method:hidden tag using the method_hidden function.