Use a class as control

PaulS

Problem

In my Xojo framework I can add a class as a special control to a window or container control.
The class is used to automatically add labels in front of fields and check if the data is the fields is filled when required or meets certain criteria.

In Objo it isn't possible to add a class as a control.

Proposed Solution

Make adding a class possible

Example Workflow

Alternatives Considered

Who Would This Help?

Garry

Thanks Paul. Just to make sure I understand the request: are you asking for Objo Studio to support designer-placeable non-visual components?

In other words, a user-defined class could be dropped onto a window/container in the designer, appear as a small design-time icon, expose its custom properties in the Inspector, and then be instantiated with the window at runtime?

For example, your cls_In_Control would not necessarily draw anything itself, but would manage or validate other controls on the window, using properties such as label width, label colour, blink exclusions, picture exclusions, etc.

A few details would help pin this down:

Is cls_In_Control a normal class, or does it inherit from a Xojo control/component base class?
Is it visible at runtime, or only represented by an icon in the designer?
How does it know which controls on the window it should manage?
Would you expect any class to be placeable this way, or only classes that inherit from a specific base type such as Control?

If that’s the intent, I’d describe this as support for non-visual components in the visual designer, rather than literally “using a class as a control”.

PaulS

Is cls_In_Control a normal class, or does it inherit from a Xojo control/component base class?
cls_In_Control is a normal class, no Superclass

Is it visible at runtime, or only represented by an icon in the designer?
No, it's not visible at runtime, just a clickable icon in the designer so you can adjust the properties

How does it know which controls on the window it should manage?
The relevant method in this is the LoopControls method
I'll send you the class, so you can see the source code on how it works.

Would you expect any class to be placeable this way, or only classes that inherit from a specific base type such as Control?
In Xojo I can drag any class in the window. If you only want to have it as non-visual components it's fine by me.
One of the most imported goals in my Framework is to get this class/non-visual component working in Objo.

Garry

Thanks Paul. This is now implemented in main and will be included in the next Studio build: https://feedback.objo.dev/feature/559

I’ve implemented this as opt-in non-visual designer components, rather than treating ordinary classes as fake visual controls.

The workflow is:

Create a normal Objo class.
Enable the Available in Visual Designer checkbox for that class.
- This can be done from the class Inspector.
- It can also be toggled from the Navigator context menu.
The class will then appear in a new Project Components section of the visual designer library.
Dragging or double-clicking it adds it to the designer shelf, not to the window/container surface.
At runtime, Studio generates it as a normal property and instantiates it with the layout owner.

For example, a component called MyService dropped onto a window as MyService1 generates code along these lines:

Private Property MyService1 As MyService

MyService1 = New MyService

It does not generate visual-control setup such as position, size, locking, typography, appearance, .Name, or Me.Add(...).

A few details:

Components are ordinary classes.
They are not visible at runtime.
They live on the designer shelf.
They can expose public writable scalar properties through Studio’s existing Inspector Behaviour system.
Classes must opt in, otherwise large projects would make the control library too noisy.
UI subclasses still appear under Project Controls.
Opted-in plain classes appear under Project Components.
App is excluded.
Built-in control subclasses are excluded from Project Components.
Classes must either have no explicit constructor, or have a public parameterless constructor.
If a component is already placed in a layout and is later opted out, it remains in the layout; it is only removed from the library.

Events are also handled separately from visual controls:

Built-in control events are not offered for components.
Project-declared events on the component class, or its inheritance chain, are offered and wired.

So this should support the same broad use case as your Xojo example: a normal non-visual class can be placed on a Window or ContainerControl, configured in the Inspector, and instantiated automatically with the layout.

PaulS

Thank you Garry! I'm very pleased with your solution.
The next days I will work on converting the Xojo class in the Objo Project component.
i'm convinced that it will work as expected. Maybe that I have some questions on how to convert certain Xojo things to Objo.

Garry

Always happy to answer questions 🙂