Qt 5.15 Standard Support for Legacy License Holders Ends Today

https://www.qt.io/blog/qt-5.15-support-ends

by jandeboevrie • 3 years ago

38 27 3 years ago

jeroenhd• 3 years ago

I only know Qt as a requirement to install for some tools and libraries. Can someone explain the significance of this? Is there a reason people still wait for LTS updates for Qt 5 instead of upgrading to Qt 6?

Edit: thank you for your responses!

_0w8t• 3 years ago

QT is used for embedded systems that may run for 10 and more years. If a device requires certification, one does not want to upgrade to a newer QT as that may require to certify the software again, while for security fixes the requirements are much more simpler.

cbhl• 3 years ago

This announcement mostly affects folks who are using Qt under paid commercial licenses. Qt 5 had "perpetual" licenses that you could buy, but for Qt 6 they switched to a SaaS monthly licensing model.

If you're using Qt applications purely in the open source world (e.g. KDE on some Linux distro) there's no new news here.

ptx• 3 years ago

There are related old news for the open source world, though, in that Qt 5.x LTS is no longer open source: https://news.ycombinator.com/item?id=25748335

gettodachoppa• 3 years ago

If you're using Qt applications purely in the open source world (e.g. KDE on some Linux distro) there's no new news here.

A lot of small businesses use Qt for free under the LGPL license (allowing them to keep their application closed-source as long as the user is free to replace the Qt dynamic libraries). For the past several years many new modules are commercial or GPL only, preventing their use by LGPL users. For example, QtWayland, QML Virtual Keyboard, WebGL, Qt Quick 3D.

Some companies would bite the bullet and pay for Qt their exorbitant fee, then let the license expire and keep using the old version. As you say, this will no longer be possible.

I find Qt 6's license policy awful, I simply don't believe in "pay us forever even if you're happy with an old version". Early on Qt 6 even had a draconian commercial policy that wouldn't allow you to distribute an old binary after if your license was expired and you stopped new development, thankfully they walked this back.

t90fan• 3 years ago

QT is used a lot in Embedded systems.

Years ago, I used to write software for medical devices which used QT, and those were supported in the wild for 10 years.

I think its also popular in cars and stuff nowadays.

EliRivers• 3 years ago

Having recently seen a product move from Qt5 to Qt6, there sure are reasons! Off the top of my head, some of the things that had to be done:

Remove every use of the previous QRegExp class (no longer existed in QT6), which was always bad, and replace it with the similar but slightly different behaving QRegularExpression class. Different enough that it's not just a simple grep.

Rip out huge chunks of XML processing code that used QT5 XML libraries that were outright withdrawn, and replace them with alternatives.

Rewrite some sound generating code to switch away from Qt5 classes that straight up no longer existed, to something else.

Rip out uses of the QT5 web engine classes; I think I recall it was replaced wholesale in QT6, but it was nothing but trouble through its life so there was an outright rewrite of everything using it to just do something non-web instead.

Any others that were outright withdrawn we also must have replaced. Can't remember them all, but here's a list: https://doc.qt.io/qt-6/whatsnew60.html#removed-modules-in-qt...

Some of those have an extended life in a QT6 "QT5 compatability module", but that's clearly not going to get a lot of security and bugfixes and there's no telling when it might vanish.

Lots of very fiddly changes to the Qt metatype system had people trawling through weird and wonderful error messages working out what was going on and how they could replace it.

QT6 demanded to be built under C++17; after switching the compiler to that, there sure was a whole lot of old code that either didn't compile at all, or flashed heavily red when the compiler looked at it, that demanded a rewrite.

All this, and when you're done, you've got something that's probably functionally about the same as what you had beforehand, but the previous version of the software under QT5 had a decade of use testing and this is brand new.

No customer is going to pay for all this effort, so there is very little impetus on anyone to move from QT5 to QT6 if the QT5 version works and updates keep coming. It's only at the end that people are finally forced to make a move.

teruakohatu• 3 years ago

Qt 5 has contributed to the largest disruption in this century in the automotive industry, making electric cars available to the masses.

That is quite a bold claim. Tesla used QT which I think they are referring to, but I don't think the choice of QT contributed to the disruption on the automobile industry.

chungy2• 3 years ago

Hey, when selling a toolkit/framework, they've gotta spin the data in their favor as much as possible. If I was in charge of Qt marketing, I'd do the same.

tensor• 3 years ago

As far as I know Qt is legit a standard for advance UI in automotive and other industrial applications. I think it's fair to say they contributed.

kramerger• 3 years ago

vscode is now the standard editor for development at Tesla.

I don't see Microsoft making such claims.

sho_hn4• 3 years ago

I'd say it's fine. Tesla is widely praised for their software experience, and Qt sells a product with the value proposition of speeding up and enabling software development. Linking the two in a marketing message isn't crazy.

And frankly, there are some technical properties of Qt that do make it well-suited to the kinds of problems car makers need to solve. For example, Qt is quite good at offering customizability and extension points at low/mid/high levels of the toolkit. It's easy to subclass/extend/replace UI controls in various ways. When you need your UI controls to do unusual things not found on other kinds of systems, for example implement regional rules for driver distraction, that's useful.

At the end of the day, there's likely more EVs on the road with Qt on them than without.

TechBro86153• 3 years ago

Isn't SpaceX using Chromium with a JavaScript app in their space capsule dashboards? It's interesting that they chose that while Tesla used Qt. Obviously the engineering teams aren't the same but I wonder if there is a story behind the two choices.

mtkd• 3 years ago

It's also the gift that keeps giving when setting up capybara-webkit on a new box

steve1977• 3 years ago

I guess it’s “contributed” in the same sense that many people use term in their CVs (as in “I happened to be in the same building when project x succeeded”)

sho_hn4• 3 years ago

Qt Company does also sell professional services and has engineers work directly on customer projects.

throwaway2037• 3 years ago

To be clear, this announcement is less scary that it sounds. Qt 5.0 was first released in 2012, and had its final release in 2023.

FloatArtifact• 3 years ago

https://github.com/rochus-keller/LeanQt

A minimum and easy to build fork of QT

Qt 5.15 Standard Support for Legacy License Holders Ends Today

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