Model/View Drag and Drop in Qt - Part 3

In this third blog post of the Model/View Drag and Drop series (part 1 and part 2), the idea is to implement dropping onto items, rather than in between items. QListWidget and QTableWidget have out of the box support for replacing the value of existing items when doing that, but there aren't many use cases for that. What is much more common is to associate a custom semantic to such a drop. For instance, the examples detailed below show email folders and their contents, and dropping an email onto another folder will move (or copy) the email into that folder.

Step 1

Initial state, the email is in the inbox

Step 2

Dragging the email onto the Customers folder

Step 3

Dropping the email

Step 4

The email is now in the customers folder

With Model/View separation

Example code can be found here for flat models and here for tree models.

Setting up the view on the drag side

☑ Call view->setDragDropMode(QAbstractItemView::DragOnly)
unless of course the same view should also support drops. In our example, only emails can be dragged, and only folders allow drops, so the drag and drop sides are distinct.

☑ Call view->setDragDropOverwriteMode(...)
true if moving should clear cells, false if moving should remove rows.
Note that the default is true for QTableView and false for QListView and QTreeView. In our example, we want to remove emails that have been moved elsewhere, so false is correct.

☑ Call view->setDefaultDropAction(Qt::MoveAction) so that the drag defaults to a move and not a copy, adjust as needed

Setting up the model on the drag side

To implement dragging items out of a model, you need to implement the following -- this is very similar to the section of the same name in the previous blog post, obviously:

class EmailsModel : public QAbstractTableModel
{
~~~
Qt::ItemFlags flags(const QModelIndex &index) const override
{
if (!index.isValid())
return {};
return Qt::ItemIsEnabled | Qt::ItemIsSelectable | Qt::ItemIsDragEnabled;
}
// the default is "copy only", change it
Qt::DropActions supportedDragActions() const override { return Qt::MoveAction | Qt::CopyAction; }
QMimeData *mimeData(const QModelIndexList &indexes) const override;
bool removeRows(int position, int rows, const QModelIndex &parent) override;

☑ Reimplement flags() to add Qt::ItemIsDragEnabled in the case of a valid index

☑ Reimplement supportedDragActions() to return Qt::MoveAction | Qt::CopyAction or whichever you want to support (the default is CopyAction only).

☑ Reimplement mimeData() to serialize the complete data for the dragged items. If the views are always in the same process, you can get away with serializing only node pointers (if you have that) and application PID (to refuse dropping onto another process). See the previous part of this blog series for more details.

☑ Reimplement removeRows(), it will be called after a successful drop with MoveAction. An example implementation looks like this:

bool EmailsModel::removeRows(int position, int rows, const QModelIndex &parent)
{
beginRemoveRows(parent, position, position + rows - 1);
for (int row = 0; row < rows; ++row) {
m_emailFolder->emails.removeAt(position);
}
endRemoveRows();
return true;
}

Setting up the view on the drop side

☑ Call view->setDragDropMode(QAbstractItemView::DropOnly) unless of course it supports dragging too. In our example, we can drop onto email folders but we cannot reorganize the folders, so DropOnly is correct.

Setting up the model on the drop side

To implement dropping items into a model's existing items, you need to do the following:

class FoldersModel : public QAbstractTableModel
{
~~~
Qt::ItemFlags flags(const QModelIndex &index) const override
{
CHECK_flags(index);
if (!index.isValid())
return {}; // do not allow dropping between items
if (index.column() > 0)
return Qt::ItemIsEnabled | Qt::ItemIsSelectable; // don't drop on other columns
return Qt::ItemIsEnabled | Qt::ItemIsSelectable | Qt::ItemIsDropEnabled;
}
// the default is "copy only", change it
Qt::DropActions supportedDropActions() const override { return Qt::MoveAction | Qt::CopyAction; }
QStringList mimeTypes() const override { return {QString::fromLatin1(s_emailsMimeType)}; }
bool dropMimeData(const QMimeData *mimeData, Qt::DropAction action, int row, int column, const QModelIndex &parent) override;
};

☑ Reimplement flags()
For a valid index (and only in that case), add Qt::ItemIsDropEnabled. As you can see, you can also restrict drops to column 0, which can be more sensible when using QTreeView (the user should drop onto the folder name, not onto the folder size).

☑ Reimplement supportedDropActions() to return Qt::MoveAction | Qt::CopyAction or whichever you want to support (the default is CopyAction only).

☑ Reimplement mimeTypes() - the list should include the MIME type used by the drag model.

☑ Reimplement dropMimeData()
to deserialize the data and handle the drop.
This could mean calling setData() to replace item contents, or anything else that should happen on a drop: in the email example, this is where we copy or move the email into the destination folder. Once you're done, return true, so that the drag side then deletes the dragged rows by calling removeRows() on its model.

bool FoldersModel::dropMimeData(const QMimeData *mimeData, Qt::DropAction action, int row, int column, const QModelIndex &parent)
{
~~~ // safety checks, see full example code
EmailFolder *destFolder = folderForIndex(parent);
const QByteArray encodedData = mimeData->data(s_emailsMimeType);
QDataStream stream(encodedData);
~~~ // code to detect and reject dropping onto the folder currently holding those emails
while (!stream.atEnd()) {
QString email;
stream >> email;
destFolder->emails.append(email);
}
emit dataChanged(parent, parent); // update count
return true; // let the view handle deletion on the source side by calling removeRows there
}

Using item widgets

Example code:

On the "drag" side

☑ Call widget->setDragDropMode(QAbstractItemView::DragOnly) or DragDrop if it should support both

☑ Call widget->setDefaultDropAction(Qt::MoveAction) so that the drag defaults to a move and not a copy, adjust as needed

☑ Reimplement Widget::mimeData() to serialize the complete data for the dragged items. If the views are always in the same process, you can get away with serializing only item pointers and application PID (to refuse dropping onto another process). In our email folders example we also serialize the pointer to the source folder (where the emails come from) so that we can detect dropping onto the same folder (which should do nothing).

To serialize pointers in QDataStream, cast them to quintptr, see the example code for details.

On the "drop" side

☑ Call widget->setDragDropMode(QAbstractItemView::DropOnly) or DragDrop if it should support both

☑ Call widget->setDragDropOverwriteMode(true) for a minor improvement: no forbidden cursor when moving the drag between folders. Instead Qt only computes drop positions which are onto items, as we want here.

☑ Reimplement Widget::mimeTypes() and return the same name as the one used on the drag side's mimeData

☑ Reimplement Widget::dropMimeData() (note that the signature is different between QListWidget, QTableWidget and QTreeWidget) This is where you deserialize the data and handle the drop. In the email example, this is where we copy or move the email into the destination folder.

Make sure to do all of the following:

any necessary behind the scenes work (in our case, moving the actual email)
updating the UI (creating or deleting items as needed)

This is a case where proper model/view separation is actually much simpler.

Improvements to Qt

While writing and testing these code examples, I improved the following things in Qt, in addition to those listed in the previous blog posts:

QTBUG-2553 QTreeView with setAutoExpandDelay() collapses items while dragging over it, fixed in Qt 6.8.1

Conclusion

I hope you enjoyed this blog post series and learned a few things.

The post Model/View Drag and Drop in Qt - Part 3 appeared first on KDAB.

03 Apr 2025 8:43am GMT

This is for everyone upgrading to Plasma 6.3.4, which was released yesterday. I suspect that some of you will notice something slightly wrong with notifications; the top padding is off, causing text to look not vertically centered most of the time.

This is my fault. The recent bug-fixes I made to notification spacings and paddings were backported to Plasma 6.3.4, but ended up missing a part that positions the text labels nicely when there's body text or an icon, and didn't notice this until after 6.3.5 was released. The fix was just merged and backported for Plasma 6.3.5, so unless your distro backports the fix (I've already emailed the appropriate mailing list about this) you'll have to live with slightly ugly label positioning until then. Sorry folks! My bad.

Once you have the fix - either because your distro backports it or because you've waited until Plasma 6.3.5 - notification text positioning should look better again:

02 Apr 2025 9:51pm GMT

Up early, enjoyed some KubeCon keynotes.
Published the next strip: the state of the roads - quality and usage (or re-purposing) of software.
Quite a startling scale of conference. Caught up with GregKH & Griffin, wandered the show floor meeting new people and trying to understand things.
Quick lunch with Jono, final hall walking, and trains home, poked at Chris' work to improve canvas rendering performance on the way here and there.
Home, dinner, band-practice with H. in the evening.

02 Apr 2025 9:00pm GMT

In Konsole Layout Automation (part 1), I wrote about how to automate opening Konsole with different tabs that ran different commands. In this post, I'll talk about doing this for layouts.

Inspiration

In the past, I needed to open two connections to the same host over ssh , and change to two different directories. I opened Konsole with a layout that had two panes. Then, Quick Commands allowed me to run a command in each pane to ssh and change to the right directory. This post will outline how to achieve that and more!

Goal: Launch a Konsole window with one tab that has multiple panes which run commands

💡 Note For more detailed instructions on using Konsole, please see the output of konsole --help and take a look at the Command-line Options section of the Konsole Handbook

A layout can save and load a set of panes. Unfortuately, it can't do anything else. We can, however, use profiles and the Quick Commands plugin to make the panes more useful.

Use case: See the output of different commands in the same window. For instance, you could be running htop in one pane and open your favorite editor in another.

Here's an overview of the steps:

Set up a layout
Use QuickCommands to run things in the panes

Set up a layout

Unfortunately, the online documentation for Konsole command line options doesn't say much about how to create a layout, or the format of its JSON file. It only mentions the command line flag --layout. Also make a note of -e which allows you to execute a command.

Fortunately, creating the layout is pretty easy. Note that a layout is limited to one tab. It will only save the window splits, nothing else. No profiles, directories, etc.

Set up a tab in Konsole with the splits you want it to have
Use View -> Save Tab Layout to save it to a .json file. (I personally recommend keeping these in a specific directory so they're easy to find later, and for scripting. I use ~/konsole-layouts).
You can then use konsole --layout ~/layout-name.json to load konsole with a tab that has the splits you saved.

Use Quick Commands to do useful things in your layout

As mentioned above, you can only save splits. you can't associate a profile, or run a command directly like you can with the tilix or kitty terminals. This has been requested. In the meantime, an easy thing you can do is load a layout and then load a profile manually in each pane. This is where Quick Commands come in. These are under Plugins - Quick Commands. (If you don't see this, contact your distro / the place you installed Konsole from).

You can use Quick Commands to run a command in each pane. You can also launch a profile (with different colors etc) that runs a command (part 1 showed how these might be used). Note, however, that running konsole itself from here will launch a new Konsole window.

End each command with || return so that you get to a prompt if the command fails.

Examples

htop || return

So, after you've launched Konsole with your layout as described above, you can do this: Go to Plugins -> Show Quick Commands Add commands you'd like to run in this session. Now, focus the pane and run a command.

Using these steps, I can run htop in one pane and nvtop in the other.

After you've gotten familiar with tabs and layouts, you can make a decently powerful Konsole session. Combine these with a shell function, and you can invoke that session very easily.

This is still too manual!

You're right. This post is about automating Konsole and having to click on things is not exactly that. You can use dbus commands in a script to load your tab layout and then run commands in each pane without using Quick Commands.

As we saw in the last post, you can use profiles to customize color schemes and launch commands. We can call those from a script in a layout. The demo scripts used below use dbus, take a look at the docs on scripting Konsole for details.

I'm using the layout file ~/konsole_layouts/monitoring.json for this example. This layout file represents two panes with one vertical split (horizontal orientation describes the panes being horizontally placed):

{
 "Orientation": "Horizontal",
 "Widgets": [
 {
 "SessionRestoreId": 0
 },
 {
 "SessionRestoreId": 0
 }
 ]
}

Here's an example of a simple script using that layout, which will launch fastfetch in one pane and btm in the other:

#!/usr/bin/env bash

# Define the commands to run
cmd1="fastfetch"
cmd2="btm"

# Opens a konsole tab with a saved layout
# Change the path to point to the layout file on your system
# KPID is used for renaming tabs

konsole --hold --layout $HOME/konsole_layouts/monitoring.json & KPID=$!

# Short sleep to let the tab creation complete
sleep 0.5

# Runs commands in Konsole panes
service="$(qdbus | grep -B1 konsole | grep -v -- -- | sort -t"." -k2 -n | tail -n 1)"

qdbus $service /Sessions/1 org.kde.konsole.Session.runCommand "${cmd1}"
qdbus $service /Sessions/2 org.kde.konsole.Session.runCommand "${cmd2}"

# Renames the tabs - optional
qdbus org.kde.konsole-$KPID /Sessions/1 setTitle 1 'System Info'
qdbus org.kde.konsole-$KPID /Sessions/2 setTitle 1 'System Monitor'

What it does:

Loads a layout with 2 panes, horizontally arranged
Runs clear and then fastfetch in the left pane; runs btm in the right pane

Wrap-up

That's how you can accomplish opening a number of panes in konsole which run different commands. Using this kind of shortcut at the start of every work / programming session saved a little time every day which adds up over time. The marketing peeps would call it "maximizing efficiencies" or something. I hope some folks find this useful, and come up with many creative ways of making konsole work harder for them.

Known issues and tips

Running konsole from a Quick Command will open a new window, even if you want to just open a new tab.
You may see this warning when using runCommand in your scripts. You can ignore it. I wasn't able to find documentation on what the concern is, exactly.

The D-Bus methods sendText/runCommand were just used. There are security concerns about allowing these methods to be public. If desired, these methods can be changed to internal use only by re-compiling Konsole. This warning will only show once for this Konsole instance.

Credits to inspirational sources

Thanks to the Cool-Konsole-setup repo, where I found an example script for using commands in a layout via qdbus. Note: The scripts in that repo did not work as-is.
This answer on Ask Ubuntu for improvements on the example scripts.

02 Apr 2025 12:00am GMT

Up early, dropped to the station early by J. Off into London for Kubecon - after various train failure and extra hacking time - evenutally arrived.
Met up with Joshua Lock. Enjoyed a series of lightning talks; very digestible - despite my rather superficial K8s understanding; lots of new FLOSS brands and apparently complicated things for managing complexity. Been a while since I've seen things like Kueue as a brand.
Got a bit more hacking done, caught up with Mirko Boehm, out to the House of Kube party from PlatCo - who kindly fed and watered lots of hackery types, with some ear-drum banging noises too.

01 Apr 2025 9:00pm GMT

Update on what happened across the GNOME project in the week from March 21 to March 28.

GNOME Core Apps and Libraries

Glycin

Sandboxed and extendable image loading and editing.

Sophie 🏳️‍🌈 🏳️‍⚧️ (she/her) reports

Glycin, the newish image loading and editing library, now supports specifying the memory format for image data an API user needs. If glycin is used with GTK, this has always been taken care of automatically. However, for other use cases, it's now possible to specify a limited set of formats the API user supports. Support for loading image data from a GInputStream or GBytes instead of GFile has also landed.

These features are important to adopt glycin in other areas in the quest to replace GdkPixbuf to make image loading more safe and enable more features like HDR image support and support for more image formats.

You can financially support my work or drop by and submit a code contribution.

GNOME Development Tools

Sysprof

A profiling tool that helps in finding the functions in which a program uses most of its time.

Georges Stavracas (feaneron) announces

Sysprof is now able to filter samples by marks. This allows for statistically relevant data on what's running when a specific mark is ongoing, and as a consequence, allows for better data analysis. You can read more here.

GNOME Builder

IDE for writing GNOME-based software.

Nokse says

This week Arduino support for GNOME Builder has been merged, providing integration with arduino-cli to compile and upload sketches to Arduino compatible boards. The new feature will be available in Builder Nightly and includes a graphical interface for managing libraries and platforms and selecting compilation/upload options. It also provides a template to start a new Arduino project. Note that you need to have arduino-cli installed to use this feature. If you encounter any issues, please go ahead and file them.

GNOME Circle Apps and Libraries

Brage Fuglseth (he/him) says

This week Bustle was accepted into GNOME Circle. Bustle lets you visualize and analyze D-Bus activity with detailed sequence diagrams. Congratulations!

Warp

Fast and secure file transfer.

Fina announces

Warp 0.9 was released with support for directly sending files via "Open With…" from Files. QR code scanning has also seen improvements, by utilizing the new QR code feature in Camera.

Eyedropper

Pick and format colors.

FineFindus reports

Eyedropper 2.1.0 has been released, featuring

RGB decimal notation

support for global shortcuts

a new way to directly enter colors, without picking them first

Download the new version on Flathub.

Third Party Projects

Bilal Elmoussaoui says

I have released a new version of oo7-cli, with the possibility to interact with the sandboxed applications keyrings or any keyring file on your system.
oo7-cli --app-id com.belmoussaoui.Authenticator list
The CLI also features a new CLI argument for attempting to repair a broken keyring (always backup your keyring file before).

JumpLink says

TypeScript type definitions for GNOME Shell 48 released

The TypeScript type definitions for GNOME Shell 48 have been updated!
This release brings improved TypeScript support for writing GNOME Shell extensions.

Based on the latest version of ts-for-gir:
→ v4.0.0-beta.23

Project page:
→ gjsify/gnome-shell

Note: This release was published shortly after the TWIG deadline,
so it will appear in next week's edition.

Capypara reports

Introducing Field Monitor, a remote-desktop client focused on accessing virtual machines.

It has first-class support for adding Proxmox or QEMU/KVM hypervisors but it can also connect to any server implementing one of the SPICE, RDP or VNC protocols.

It can also open RDP or Virt Viewer files.

This is the first release and it might still be a little rough around the edges in some parts, so any and all feedback is more than welcome :).

Field Monitor is powered by RDW, a set of remote-desktop widgets for GTK 4. I want to thank Marc-André Lureau, the author, since without them this app would not be possible!

Sebastian Wiesner reports

Picture Of The Day is a new app to get a picture of the day as your daily wallpaper, from NASA Astronomy Picture of the Day, Bing, Wikimedia, or Simon Stålenhag artwork.

Preview images, pick your favorite source, enable automatic updates, and enjoy a fresh wallpaper every day.

Available on Flathub.

Fractal

Matrix messaging app for GNOME written in Rust.

Kévin Commaille reports

It's the beginning of bee season! 🌸🌺🌼 🐝 B like beta! Here's Fractal 11.beta:

New shortcuts Ctrl + Page Up and Ctrl + Page Down go to the previous/next room in the list

The media cache will now be periodically cleaned up

The page that lists user sessions has been overhauled, with details moved to subpages, for a less cluttered feel, and paving the way to a new feature!

A couple of small cosmetic changes have landed as well

As usual, this release includes other improvements, fixes and new translations thanks to all our contributors, and our upstream projects.

It is available to install via Flathub Beta, see the instructions in our README.

As the version implies, there might be a slight risk of regressions, but it should be mostly stable. If all goes well the next step is the release candidate!

If you have a little bit of time on your hands, you can try to fix one of our newcomers issues. Anyone can make Fractal better!

Events

Kristi Progri reports

We're excited to announce that registrations for GUADEC are now open! https://events.gnome.org/event/259/registrations/

If you are planning to attend our event (in-person or online) now it's the time to get your ticket!

That's all for this week!

See you next week, and be sure to stop by #thisweek:gnome.org with updates on your own projects!

28 Mar 2025 12:00am GMT

Linux 6.14 is the second release of 2025, and as usual Igalia took part on it. It's a very normal release, except that it was release on Monday, instead of the usual Sunday release that has been going on for years now. The reason behind this? Well, quoting Linus himself:

I'd like to say that some important last-minute thing came up and delayed things.

But no. It's just pure incompetence.

But we did not forget about it, so here's our Linux 6.14 blog post!

A part of the development cycle for this release happened during late December, when a lot of maintainers and developers were taking their deserved breaks. As a result of this, this release contains less changes than usual as stated by LWN as the "lowest level of merge-window activity seen in years". Nevertheless, some cool features made through this release:

NT synchronization primitives: Elizabeth Figura, from Codeweavers, is know from her work around improving Wine sync functions, like mutexes and semaphores. She was one the main collaborators behind the futex_waitv() work and now developed a virtual driver that is more compliant with the precise semantics that the NT kernel exposes. This allows Wine to behave closer to Windows without the need to create new syscalls, since this driver uses ioctl() as the front-end uAPI.
RWF_UNCACHED: Linux has two ways of dealing with storage I/O: buffered I/O (usually the preferred one) that stores data in a temporary buffer and regularly syncs the cache data with the device; and direct I/O that doesn't use cache and always writes/reads synchronously with the storage device. Now a new mixed approach is available: uncached buffered I/O. This method is aimed to have a fast way to write or read data that will not be needed again in the short term. For reading, the device writes data in the buffer and as soon as the user finished reading the buffer, it's cleared from the cache. For writing, as soon as userspace fills the cache, the device reads it and removes it from the cache. In this way we still have the advantage of using a fast cache but reducing the cache pressure.
amdgpu panic support: AMD developers added kernel panic support for amdgpu driver, "which displays a pretty user friendly message on the screen when a Linux kernel panic occurs" instead of just a black screen or a partial dmesg log.

As usual Kernel Newbies provides a very good summary, you should check it for more details: Linux 6.14 changelog. Now let's jump to see what were the merged contributions by Igalia for this release!

DRM

For the DRM common infrastructure, we helped to land a standardization for DRM client memory usage reporting. Additionally, we contributed to improve and fix bugs found in drivers of AMD, Intel, Broadcom, and Vivante.

AMDGPU

For the AMD driver, we fixed bugs experienced by users of Cosmic Desktop Environment on several AMD hardware versions. One was uncovered with the introduction of overlay cursor mode, and a definition mismatch across the display driver caused a page-fault in the usage of multiple overlay planes. Another bug was related to division by zero on plane scaling. Also, we fixed regressions on VRR and MST generated by the series of changes to migrate AMD display driver from open-coded EDID handling to drm_edid struct.

Intel

For the Intel drivers, we fixed a bug in the xe GPU driver which prevented certain type of workarounds from being applied, helped with the maintainership of the i915 driver, handled external code contributions, maintained the development branch and sent several pull requests.

Raspberry Pi (V3D)

We fixed the GPU resets for the Raspberry Pi 4 as we found out to be broken as per a user bug report.

Also in the V3D driver, the active performance monitor is now properly stopped before being destroyed, addressing a potential use-after-free issue. Additionally, support for a global performance monitor has been added via a new DRM_IOCTL_V3D_PERFMON_SET_GLOBAL ioctl. This allows all jobs to share a single, globally configured perfmon, enabling more consistent performance tracking and paving the way for integration with user-space tools such as perfetto.

A small video demo of perfetto integration with V3D

etnaviv

On the etnaviv side, fdinfo support has been implemented to expose memory usage statistics per file descriptor, enhancing observability and debugging capabilities for memory-related behavior.

sched_ext

Many BPF schedulers (e.g., scx_lavd) frequently call bpf_ktime_get_ns() for tracking tasks' runtime properties. bpf_ktime_get_ns() eventually reads a hardware timestamp counter (TSC). However, reading a hardware TSC is not performant in some hardware platforms, degrading instructions per cycyle (IPC).

We addressed the performance problem of reading hardware TSC by leveraging the rq clock in the scheduler core, introducing a scx_bpf_now() function for BPF schedulers. Whenever the rq clock is fresh and valid, scx_bpf_now() provides the rq clock, which is already updated by the scheduler core, so it can reduce reading the hardware TSC. Using scx_bpf_now() reduces the number of reading hardware TSC by 50-80% (e.g., 76% for scx_lavd).

Assorted kernel fixes

Continuing our efforts on cleaning up kernel bugs, we provided a few fixes that address issues reported by syzbot with the goal of increasing stability and security, leveraging the fuzzing capabilities of syzkaller to bring to the surface certain bugs that are hard to notice otherwise. We're addressing bug reports from different kernel areas, including drivers and core subsystems such as the memory manager. As part of this effort, several fixes were done for the probe path of the rtlwifi driver.

Check the complete list of Igalia's contributions for the 6.14 release

Authored (38)

Changwoo Min

Christian Gmeiner

Luis Henriques

fuse: fix possible deadlock if rings are never initialized

Maíra Canal

Melissa Wen

Ricardo Cañuelo Navarro

Rodrigo Siqueira

Thadeu Lima de Souza Cascardo

Tvrtko Ursulin

Reviewed (36)

André Almeida

Christian Gmeiner

Iago Toral Quiroga

Jose Maria Casanova Crespo

drm/v3d: Assign job pointer to NULL before signaling the fence

Luis Henriques

Maíra Canal

Tvrtko Ursulin

Tested (2)

André Almeida

ASoC: cs35l41: Fallback to using HID for system_name if no SUB is available

Christian Gmeiner

hexagon: fix using plain integer as NULL pointer warning in cmpxchg

Acked (1)

Iago Toral Quiroga

drm/v3d: Fix miscellaneous documentation errors

Maintainer SoB (6)

Maíra Canal

Tvrtko Ursulin

28 Mar 2025 12:00am GMT

Hi all!

This month I've finally finished my initial work on HDR10 support for wlroots! My branch supports playing both SDR and HDR content on either an SDR or HDR output. It's a pretty basic version: wlroots only performs very basic gamut mapping, and has a simple luminance multiplier instead of proper tone mapping. Additionally the source content luminance and mastering display metadata isn't taken into account. Thus the result isn't as good as it could be, but that can be improved once the initial work is merged!

HDR video on a HDR screen on Sway

I've also been talking with dnkl about blending optical color values rather than electrical values in foot ("gamma-correct blending"). Thanks to the color-management protocol, foot can specify that its buffers contain linearly encoded values (as opposed to the default, sRGB) and can implement this blending method without sacrificing performance. See the foot pull request for more details.

We've been working on fixing the few last known blockers remaining for the next wlroots release, in particular related to scene-graph clipping, custom modes, and explicit synchronization. I hope we'll be able to start the release candidate dance soon.

The NPotM is Bakah, a small utility to build Docker Bake configuration files with Buildah (the library powering Podman). I've written more about the motivation and design of this tool in a separate article.

I've released tlstunnel 0.4 with better support for certificate files and some bugfixes. The sogogi WebDAV file server got support for graceful shutdown and Unix socket listeners thanks to Krystian Chachuła. Last, mako 1.10 adds a bunch of useful features such as include directives, more customization for border sizes and icon border radius, and a --no-history flag for makoctl dismiss.

See you next month!

15 Mar 2025 10:00pm GMT

This time I have three topics.

First, I want to promote the blog post I wrote to celebrate the landing of the Wayland color-management extension into wayland-protocols staging area. It's a brief historique of the journey.

Second, I want to discuss SDR and HDR video modes on monitors and TVs. I have seen people expect that the same sRGB content displayed on the SDR video mode and the HDR (BT.2100/PQ) video mode on the same monitor will look the same, and they can arbitrarily switch between the modes at any time. I have argued that this is a false expectation. Why?

Monitors tend to have a slew of settings. I tend to call them monitor "knobs". There are brightness, contrast, color temperature, picture mode, dynamic contrast, sharpness, gamma, and whatever. Many people have noticed that when the video source puts the monitor into BT.2100/PQ video mode, the monitor locks out some settings, often brightness and/or contrast included. So, SDR and HDR video modes do not play by the same rules. Hence, one cannot generally expect a match even if the video source does everything correctly.

Third, there is marketing. Have a look at the first third of this video. They discuss video streaming services, TV selling, and HDR from the picture quality point of view. My take of that is, that (some? most?) monitors and TVs come with a screaming broken picture out-of-the-box because marketing has to sell them. If all displays displayed a given content as intended, they would all look the same, major technology differences notwithstanding, but marketing wants to make each individual stand out.

Have you heard of TV calibration services? If I buy a new TV from a local electronics department store, they offer a calibration service, for a considerable additional fee. Why would anyone need a calibration service, the factory settings should be good, right?

13 Mar 2025 9:40am GMT

fidzu : desktop

03 Apr 2025

Model/View Drag and Drop in Qt - Part 3

With Model/View separation

Setting up the view on the drag side

Setting up the model on the drag side

Setting up the view on the drop side

Setting up the model on the drop side

Using item widgets

On the "drag" side

On the "drop" side

Improvements to Qt

Conclusion

02 Apr 2025

Inspiration

Goal: Launch a Konsole window with one tab that has multiple panes which run commands

Set up a layout

Use Quick Commands to do useful things in your layout

This is still too manual!

Wrap-up

Known issues and tips

Credits to inspirational sources

01 Apr 2025

28 Mar 2025

GNOME Core Apps and Libraries

Glycin

GNOME Development Tools

Sysprof

GNOME Builder

GNOME Circle Apps and Libraries

Warp

Eyedropper

Third Party Projects

Fractal

Events

That's all for this week!

DRM

AMDGPU

Intel

Raspberry Pi (V3D)

etnaviv

sched_ext

Assorted kernel fixes

Check the complete list of Igalia's contributions for the 6.14 release

Authored (38)

Changwoo Min

Christian Gmeiner

Luis Henriques

Maíra Canal

Melissa Wen

Ricardo Cañuelo Navarro

Rodrigo Siqueira

Thadeu Lima de Souza Cascardo

Tvrtko Ursulin

Reviewed (36)

André Almeida

Christian Gmeiner

Iago Toral Quiroga

Jose Maria Casanova Crespo

Luis Henriques

Maíra Canal

Tvrtko Ursulin

Tested (2)

André Almeida

Christian Gmeiner

Acked (1)

Iago Toral Quiroga

Maintainer SoB (6)

Maíra Canal

Tvrtko Ursulin

15 Mar 2025

13 Mar 2025