RichTextLabel (RTL): add_text(), append_text(), add_image() (and probably others) do not work on orphan RTL

[neoentest2]

Tested versions

Reproducible in: v4.4.dev7.official [46c8f8c], v4.3.stable.official [77dcf97]

System information

Godot v4.4.dev7 - Windows 11 (build 22631) - Multi-window, 1 monitor - Vulkan (Forward+) - dedicated NVIDIA GeForce MX450 (NVIDIA; 32.0.15.5613) - 11th Gen Intel(R) Core(TM) i7-1165G7 @ 2.80GHz (8 threads)

Issue description

add_text(), append_text(), add_image() and probably other similar functions do not work on orphan RichTextLabel. Setting the text property directly works.

In the Minimal reproduction project, I only used append_text(), but in my current project in v4.3.stable.official add_image() doesn't work either.

I think it's a bug because I didn't find anything that explains why it behaves like that.
It's pretty simple to bypass putting add_child() before add_(). Deferring the add_ functions works too. However, I think it's not the expected behavior.

Steps to reproduce

• Create a RichTextLabel by code (instantiating a scene or creating a new RTL with enough size)
• Add some text using add_text() or append_text()
• Add the RTL to the tree with add_child()

Can be done on a brand new project. I added a Minimal reproduction project anyway.

Minimal reproduction project (MRP)

orphan_RTL_test.zip

[AThousandShips]

Sounds like:

• RichTextLabel: Newly Instanced RichTextLabel's add_text() and append_text() don't add to text #94630

[neoentest2]

Sounds like:

• RichTextLabel: Newly Instanced RichTextLabel's add_text() and append_text() don't add to text #94630

I looked at that issue too, but in my understanding it's a different topic. That issue revolves around how the text property is not updated with add_text (and I got it why), but the label is still showing correctly. I just tested it: I put the text += operation at the beginning (because it will clear the tag stack otherwise), and I gave the new label some size, and it works correctly, even if the text property is not the same as the text shown:

In my issue, if the RTL is orphan, it doesn't show the things added with add_*(); I'm not considering the text property at all.

[neoentest2]

After some experiments and looking at the code, I think I found the issue: it's the _notification() behavior of rich_text_label.cpp:

	case NOTIFICATION_ENTER_TREE: {
		_stop_thread();
--->		if (!text.is_empty()) {
--->			set_text(text);
		}

		main->first_invalid_line.store(0); // Invalidate all lines.
		queue_redraw();
	} break;

I did some testing. When the RLT is added to a tree, if the text isn't empty, it looks like it calls set_text, replacing the stack with the text property. Calling add_text() to an empty RTL before adding it to the tree works as expected (this confused me a lot, since it works some of the time, before I decided to dig deep into this. And it's probably why this behavior manages to stay hidden).

I don't know why it's necessary to call set_text() on tree enter, nor how to fix this. I really don't know how Godot works.

If you can confirm my findings, I would change the title of the issue to something like: "RichTextLabel: if the text property isn't empty, it calls set_text() on tree entering, silently clearing the stack."