GType registration order issue

[Daniel15]

Version: 0.8.0-preview1

I have a PressAndHoldButton.cs that subclasses Button. It does not use a template:

/// <summary>
/// A button that emits events while it is being held in.
/// </summary>
[GObject.Subclass<Button>(qualifiedName: nameof(PressAndHoldButton))]
public partial class PressAndHoldButton
{
	....
}

I have a PanAndTiltButtons.blp Blueprint file that uses this component:

using Gtk 4.0;

template $PanAndTiltButtons : Grid {
  column-spacing: 4;
  row-spacing: 4;

  $PressAndHoldButton _up {
    tooltip-text: _('Up');
    icon-name: 'go-up';
    width-request: 50;
    height-request: 50;

    layout {
      row: '0';
      column: '1';
    }
  }
...

This compiles to PanAndTiltButtons.ui:

<?xml version="1.0" encoding="UTF-8"?>
<!--
DO NOT EDIT!
This file was @generated by blueprint-compiler. Instead, edit the
corresponding .blp file and regenerate this file with blueprint-compiler.
-->
<interface>
  <requires lib="gtk" version="4.0"/>
  <template class="PanAndTiltButtons" parent="GtkGrid">
    <property name="column-spacing">4</property>
    <property name="row-spacing">4</property>
    <child>
      <object class="PressAndHoldButton" id="_up">
        <property name="tooltip-text" translatable="yes">Up</property>
        <property name="icon-name">go-up</property>
        <property name="width-request">50</property>
        <property name="height-request">50</property>
        <layout>
          <property name="row">0</property>
          <property name="column">1</property>
        </layout>
      </object>
    </child>
    .....

which is used in PanAndTiltButtons.cs:

/// <summary>
/// Renders up, down, left, and right buttons to adjust the pan and tilt.
/// </summary>
[GObject.Subclass<Grid>(qualifiedName: nameof(PanAndTiltButtons))]
[Template<EntryAssemblyResource>("PanAndTiltButtons.ui")]
public partial class PanAndTiltButtons
{
	[Connect] private PressAndHoldButton _up;
	...
}

When I run the app, I get this error:

(webcamcontrol:44449): Gtk-CRITICAL **: 14:33:47.628: Error building template class 'PanAndTiltButtons' for an instance of type 'PanAndTiltButtons': .:0:0 Invalid object type 'PressAndHoldButton'

because the PressAndHoldButton GType isn't registered yet at the time the PanAndTiltButtons instance is created. Manually calling PressAndHoldButton.GetGType() before creating the PanAndTiltButtons instance works, which is the workaround I'm using for now.

Is this something that Gir.Core could handle itself? Automatically register subclasses on app init rather than lazily when GetGType is called?

[badcel]

The topic is a bit tricky and I did not document it yet. But it probably should be documented so I added it to #1410.

So let's go into some detail: there is some way to automatically execute code from the dotnet runtime during assembly load. I tried to use it already 2 times. But it is actively discouraged by the dotnet runtime pretty explicitly: https://learn.microsoft.com/en-us/dotnet/fundamentals/code-analysis/quality-rules/ca2255

So there is a generated method to support this: https://github.com/gircore/gir.core/blob/main/src/Samples/Gtk-4.0/CompositeTemplate/Program.cs#L5

It has one flaw without a good solution: it requires all dependent GirCore libraries to be initialized first. See the sample which initializes adwaita first and the adwaita based subclasses second.

Any idea how this could be improved is very welcome.