Built-in icon cannot be found in Gnome Builder

Development
1

I am trying to use the tab-new-symbolic icon in my GTK4 project like this:

<object class="GtkButton">
  <property name="action-name">win.new-tab</property>
  <property name="tooltip-text" translatable="yes">Open a new tab</property>
  <property name="focus_on_click">False</property>
  <property name="icon-name">tab-new-symbolic</property>
</object>

This button is in the header bar. The GTK Icon Browser shows this icon with this exact name. I also found this icon in the icons folder of my SDK:

ls -al /home/user/.local/share/gnome-builder/flatpak/runtime/org.gnome.Sdk/x86_64/master/7683223a8ac1c3520e4f2b9e50bb9e8f8f9d8a60f67bca2ae80a2da68a28bc73/files/share/icons/Adwaita/symbolic/actions/tab-new-symbolic.svg

Yet, when building the app, it only shows a placeholder. I have checked Meld, which also uses that icon and it appears that it just uses it.

How can I use this symbol? Do I have to register it first?

2

That’s odd, it should just work. My first troubleshooting step in GNOME Builder is always to clean and rebuild the app, just to make sure it’s not some caching problem.

3

Thanks for the confirmation. I also find it odd that this symbol isn’t found by default.

I was originally working with the Builder app from the Ubuntu 24.04 repositories. Hence, I installed Builder from flathub and opened my project therein, but the symbol didn’t work there as well. I also updated the Gnome SDKs and platform in Builder’s settings.

To verify, whether this is really a problem of my environment, I started a live session of Zorin OS 18 and installed Builder 49.1 from flathub with the command-line. In Builder, I created a new example Python-based Gnome application project. After having opened the project, it prompted me to install Gnome SDK, platform and docs 48, which I confirmed. After installation, I hit run and the example window opened as expected. Then, I opened src/window.ui and changed the symbol of the menu to tab-new-symbolic. Restarting the app yielded the same behavior that I see in my current project: The button’s symbol is a placeholder (a white sheet with a triangle and an exclamation mark inside).

In my understanding, this should work, isn’t this the cleanest environment you can get?

So, I guess, there’s probably some magic that has to be done to make it work?

EDIT: My Project is a Python project and I selected the “GNOME application” template when I created it. Just to make sure, the C template also shows the same issue.