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Immediate – Happenings in GNOME

Immediate – Happenings in GNOME

2023-12-15 16:09:25

Prompt is a terminal that marries the very best of GNOME Builder’s seamless container help, the fantastic thing about GNOME Text Editor, and the robustness of VTE. I like to think about it as a companion terminal to Builder.

Although it’s additionally helpful for immutable/container-oriented desktops like Fedora Silverblue or Project Bluefin the place containers are front-and-center.

A screenshot of Prompt with a menu open showing a list of available containers to spawn a new terminal shell within.

This got here out of a prototype I made for the GNOME Builder IDE practically a decade in the past. We already had all of the container abstractions so why not expose them as a Terminal Workspace?

Immediate extracts the container portion of the code-foundry right into a standalone program.

My prototype didn’t go wherever in recent times as a result of I used to be conflicted. I’ve a excessive efficiency bar for software program I ship and VTE wasn’t there but on Wayland-based compositors which I exploit. However for those who frequent this weblog you already know that I reached out to the meticulous VTE maintainers and helped them decide the appropriate battles to just about double efficiency this GNOME cycle. I additionally ported gnome-terminal to GTK 4 which offered me ample alternative to see the place and the way containers would combine from an software perspective.

I designed Immediate to be Flatpak-first. That has design implications if you’d like a strong feature-set. Sometimes an software is restricted to the PID and PTY namespace inside the Flatpak sandbox even for those who’re able to executing processes on the host. Which means utilizing TTY API like tcgetpgrp() turns into completely ineffective when the kernel ioctl() returns you a PID of 0 (because it’s in a distinct namespace). Notably, 0 is the one worth tcgetpgrp() just isn’t documented to return. How enjoyable!

To provide Immediate the very best probability at monitoring containers and foreground processes a prompt-agent runs from the host system. It’s restricted to very previous variations of GLib/GObject/GIO and JSON-GLib as a result of we all know that /usr/bin/flatpak will already require them. Utilizing these libraries as a substitute of sure GLibc API helps us in conditions the place GLibc is barely forward-compatible and never backwards-compatible. Mixed with point-to-point D-Bus serialization on high of a socketpair() we’ve a strong option to go file-descriptors between the agent and the UI course of and we’ll use {that a} bunch.

There are a number of little tips in right here to maintain issues quick and keep away from energy-drain. For instance, course of monitoring is completed with a mix of exponential-backoff and re-triggering primarily based on both new content material arriving or sure key-presses. It offers a really low-latency feeling to the sudo/ssh characteristic I like from Console, albeit with much less overhead.

One factor I discover useful with Builder is that after I come again to it my challenge session is correct there. So this has session help too. It can restore your tabs/containers how they have been earlier than. So when you have an identical workflow you may discover that helpful. If not? Simply flip it off in Preferences.

I need to have a little bit of enjoyable as a result of proper now I’m caught indoors caring for my younger, paraplegic canine. So it’s packed filled with palettes you possibly can play with. Who doesn’t like a bit colour!

A screenshot of Prompt with the preferences window open allowing the selection of numerous palettes with diverse color sets. The terminal window is recolored using colors from the palette.

There are some refined efficiency selections that make for a greater expertise in Immediate. For instance, I do like having a small quantity of padding across the terminal in order that rounded corners look good and in addition avoids an additional framebuffer when rendering on the GPU. Nevertheless, that appears odd with scrollback. So Immediate rewrites the snapshot from VTE to take away the background and extraneous clipping. We have already got a background from window recoloring anyway. It’s a small element that simply feels good when utilizing it.

One other refined enchancment is detecting once we are coming into the tab overview. At present, libadwaita makes use of a GtkWidgetPaintable to symbolize the tab contents. This works nice for the likes of Epiphany the place the contents are backed by GL textures. However for a terminal software we’ve a number of textual content and we don’t need to redraw it scaled as would occur on this case. That places a number of stress on the glyph cache. So as a substitute, we create a single texture upfront and scale that texture. A lot smoother.

See Also

For individuals writing terminal purposes there’s a little inspector you possibly can popup that will help you out. It may be troublesome to know for those who’re doing the appropriate factor or getting the appropriate conduct so this may be one thing we are able to prolong going ahead to make that simpler for you. GTK’s inspector already does a lot so that is simply an extension of what you could possibly do there.

A terminal window open with a secondary "inspector" window open. The inspector shows what column and row the mouse is positioned as well as the cursor and what non-visible OSC hyperlink is under the pointer.

Creating Immediate has elevated issues we should always repair.

  • Podman creates a further PTY which form of breaks the entire notion of foreground processes. Filed an issue upstream and it appears seemingly we are able to get that addressed for private containers. That can enhance what occurs once you shut your terminal tab with one thing working or for those who SSH’d into one other host from the container.
  • Container monitoring is at present restricted to Fedora hosts as a result of toolbox solely emits the container-tracking escape sequences when the host is Fedora. The present purpose I’ve mentioned with VTE maintainers is that we’ll use a brand new “termprop” characteristic in VTE that will probably be silently dropped on terminal purposes not enthusiastic about it. That means toolbox and the likes can safely emit the escape sequence.
  • At present podman will exit for those who go a --user or --workdir that doesn’t exist within the container. That isn’t an issue with toolbox as it’s at all times your person and fails gracefully for directories. So we’d like a very good technique to see if each of these can be found to inherit when creating new tabs.
  • This does have transparency help, however it’s hidden in a GSetting for now. As soon as we’ve libadwaita with CSS variable help we are able to in all probability make this look higher throughout transitions which is the place it falls down now. We additionally want some work on how AdwTabOverview does snapshots of tabs and inserts a background.
  • I’ve a .bashrc snippet to deal with jhbuild as a container which is useful for these of us GNOME builders nonetheless utilizing it.
  • Accessibility is a particularly vital piece of our infrastructure in GNOME. So a part of this work will inevitably tie into ensuring the a11y portion of VTE works with the soon-to-land a11y enhancements in GTK. That has at all times been lacking on GTK 4-based VTE and due to this fact each terminal primarily based upon it.

$ flatpak set up --user --from https://nightly.gnome.org/repo/appstream/org.gnome.Prompt.Devel.flatpakref

If you happen to like software program that I write, take into account donating to a pet shelter close to you this vacation season. We’re so fortunate to have nice pet care in Oregon however not all over the place is so fortunate.

Glad Vacation Hacking!

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