Show HN: Qt binding for Go with support for all major operating systems

https://therecipe.github.io/qt

by therecipe • 9 years ago

222 73 9 years ago

therecipe.github.io

cridenour• 9 years ago

Have used it and hang out in the Gophers slack channel. You provide great support and when I followed instructions it worked perfect!

therecipe15• 9 years ago

thank you :)

educar• 9 years ago

Why is the -fast flag not the default for qtdeploy?

Edit: er, why the downvotes for a harmless question? I was curious why a flag named fast is not the default. This question is also very much related to the project page linked.

therecipe15• 9 years ago

qtdeploy is intended to be used for deploying and therefore will run qtrcc, qtmoc, qtminimal and do the actual bundling of your binary. the -fast flag re-uses the cached rcc_* moc_* minimal-* files and will also not re-run the actual bundling process. this works for the desktop targets but not for the mobile targets, therefore I made it optional.

scott_karana• 9 years ago

In what world would "fast" mean "do things faster with no downsides"? ;)

It's a trade-off between deployment speed and quality, like compiler optimizations.

dejv• 9 years ago

I am confused by QT licensing model. What are limitation of free QT plan used by commercial (downloadable) application?

brcha2• 9 years ago

Qt is LGPL. So there are no limitations unless you make changes to the Qt library (which you probably won't do). If you do make changes, though, then you would have to release them under LGPL license.

So, I think there are absolutely no limitations to using Qt LGPL in a commercial application. All you get from the commercial license is support.

Note: I'm not a lawyer, don't hang me if you get sued or something. But I do think I'm right about this.

chrisseaton2• 9 years ago

there are no limitations unless you make changes to the Qt library

I thought you were required to allow linking to a newer or modified version of a LGPL library? So one limitation is you have to either dynamically link or provide a mechanism to relink.

Matthias247• 9 years ago

It's also in the meantime LGPLv3 - at least for certain QT components, but the system is not easy to understand. The v3 requirements add that if you distribute an application (or device) with it, you have to provide the user with a way to update the linked QT library with a different version that he provides himself.

slavik812• 9 years ago

The open source version of Qt is LGPL, which basically means you may use it in a proprietary application if you use dynamic linking. If you link statically or copy any of its code, then your program must be free software (GPL).

If you pay for a commercial license, you can link statically without restriction. The commercial version is also necessary for locked-down platforms like iOS where the dynamic linking can't be changed by the end user of the software.

IANAL, and there are a few details I glossed over, but that's the simple version.

Nokinside• 9 years ago

Either dynamic linking or provide object files that can be linked with the library.

In essence, you can use it in proprietary application as long as you don't modify the library and you provide means to switch to different version of the library.

donatj• 9 years ago

If I statically link is my code inherintly LGPL or could I still license MIT?

hurd• 9 years ago

"If you link statically or copy any of its code, then your program must be free software (GPL)." I don't the first part is true (the second one is though).

https://www.gnu.org/licenses/gpl-faq.en.html#LGPLStaticVsDyn...

simfoo2• 9 years ago

It seems the obscure qt.io Downloads page really isn't helping in this regard

01walid2• 9 years ago

dumb question: will qtdeploy produce a single static binary for the whole app or is about some other sort of shared libraries deployment ?

therecipe15• 9 years ago

it depends on the target [1] and which Qt version you use, the default "official" Qt version usually dynamically links against Qt's libs. for windows for example you can use the msys2 version (on windows), which can also be statically linked or you could use the docker images with mxe to statically link your windows application. but you could also build a static version of Qt yourself and use that version as well.

https://github.com/therecipe/qt#targets

learc83• 9 years ago

I may be remembering wrong. But I believe back when I used Qt a few years ago, the most common interpretation of the GPL license the free version used prevented you from deploying with a single static binary.

01walid2• 9 years ago

Oh right, almost forgot that..

e12e2• 9 years ago

Surely, that's "prevent you from deploying with a single static binary unless under the GPL/binding offer of source code"?

simfoo2• 9 years ago

Qt is LGPL'd, meaning static linkage is possible as long as others are able to relink using other Qt versions. Providing your applications as object files is enough for this, no need to share sources.

pspeter3• 9 years ago

Does this require CGo?

TheDong• 9 years ago

Yes. For example, the dbus package: https://github.com/therecipe/qt/blob/053d54a2eb0658bae6e3259...

https://github.com/therecipe/qt/blob/053d54a2eb0658bae6e3259...

All of the code is cgo wrappers around messes of c/c++

infogulch• 9 years ago

Can gc load a cgo plugin [1]? If so, could you build therecipe/qt into a plugin and load it at runtime to avoid being forced to use cgo?

E.g. your project has `type Qt interface {`, and the plugin exports a global symbol that can be asserted to that interface to use the library.

[1] https://golang.org/pkg/plugin/

mike_ivanov4• 9 years ago

Is the wrapper C++ code generated or hand-written?

therecipe15• 9 years ago

it's automatically generated against the Qt version you use when you run the setup. the generator is also used to power qtmoc and qtminimal.

mike_ivanov4• 9 years ago

I couldn't find the source code of that generator. It is not here, right? -> https://github.com/therecipe/qt/

mike_ivanov4• 9 years ago

To clarify myself, I wondered if the wrapper code is generated (like here https://github.com/therecipe/qt/blob/master/websockets/webso...), not the moc-generated code.

znpy• 9 years ago

Is this an official package?

therecipe15• 9 years ago

eberkund2• 9 years ago

Does this work on embedded devices without desktop environment?

therecipe15• 9 years ago

If Qt supports it, then you can probably get it working with this binding as well.

niccl• 9 years ago

IS a beaglebone black sufficiently close to a raspberry pi3 that I can use the RPI3 environment for beaglebone black dev? If not, what's required to implement on a new platform?

eberkund2• 9 years ago

https://doc.qt.io/qt-5/embedded-linux.html

gwenzek• 9 years ago

what are the differences with go-qml? https://github.com/go-qml/qml/blob/v1/README.md

therecipe15• 9 years ago

go-qml, like the name suggests allows you to use QML together with Go. This binding allows you to also use Qt's C++ API. And it contains some tools to simplify deployment and development processes.

AsyncAwait• 9 years ago

Just wanted to say, thanks for working on this! :-)

kingmanaz• 9 years ago

I would be nice if Google put resources behind a project like this. Same with gopherjs.

golem14• 9 years ago

Nice to see this happening.

FYI, the 'examples' link on that page is broken

homarp• 9 years ago

it works from the README on github and goes to https://github.com/therecipe/qt/tree/master/internal/example...

overgard• 9 years ago

I'm a bit confused by the docker part and emphasis on deployment. Is that just for contributors/early adopters because theres no release yet, or is that just part of the flow of using this?

therecipe15• 9 years ago

It depends on how much you want to embrace docker. In general you can use this binding without touching docker at all. But if you want, you can use docker in every step of the process. It starts with the minimal setup that just depends on Go + Docker. Then continues during development, so if you would want for example test your application on android really quick, then you would just need to pull the android image instead of setting up the android SDK, NDK and JDK by yourself. And then in the end you can use docker for your CI and CD processes as well. For example by creating your own docker images on top of provided ones.

farrisbris• 9 years ago

I've been using c++/Qt for quite some time now, but i really prefer to work in go. Feels like i'm a lot more productive while writing, and i don't have to spend doubledigit minutes waiting for stuff to compile.

I recently stumbled over this project and have been using it quite a lot since. It works really well and coming from Qt-land it was really easy to use the provided bindings and generate the 'classes' for signals/slots. AND the docker images are great for cross compilation. They just work :). Thank you so much for working on this.

ball_of_lint• 9 years ago

I recently tried out gold linker in a c++/qt project, and it nearly halved my compile time. I don't quite have incremental linking working yet, but I expect it to be even better.

therecipe15• 9 years ago

thank you :)

pbnjay• 9 years ago

I'm curious how this affects file sizes? I like my static binaries and portability, but I fear this would make things balloon quite a bit to get the same broad distribution.

I've been planning on using an embedded webkit + html app in an upcoming desktop project. Are there any resources for how difficult it would be to learn Qt and create a reasonable portable, easily downloadable app?

ori_b• 9 years ago

I'd take a look at QT Quick.

therecipe15• 9 years ago

The file size depends on the target and what modules you use, for dynamically linked projects I would guess it's around 50mb for an average project. Maybe 20mb more on windows because of the icu libs, but those can be replaced with your own (much smaller) versions. Static projects may weight half of what the dynamic ones do, so maybe around 25mb. But depending on how much you care about file size, you could also compile your own static Qt version and then strip everything that you don't need.

Here [1] are some infos about QML development and here [2] you can try out QML in the browser.

[1] https://github.com/Esri/arcgis-appstudio-samples/wiki/Unders... [2] https://qmlweb.github.io

edwinyzh• 9 years ago

I also prefer golang over c++ for simplicity. But does it have IDE support? I mean Qt Creator. In the meantime, my first choice for cross-platform GUI development is Lazarus - clean language, broad OS support, and full IDE support (drag-and-drop layout designing and integrated debugging).

GoodbyeEarl2• 9 years ago

Sorry for the newbie question, I've never written a desktop application. But do you write the UI in a different language than you write its business logic? For instance, you would write the UI in Delphi with the Lazarus IDE and then the "back-end" of your app would be written in C++, Go or something alike?

uvatbc• 9 years ago

tl;dr: sometimes the UI can be written in a different language.

Qt used to have an XML markup language that auto generated C++ UI code.

Later, QML was introduced - which is a JavaScript based UI runtime.

There are Qt bindings for other languages, for example Python. So you could write business logic in Python and UI in QML.

oneweekwonder• 9 years ago

So you write Object Pascal code? You don't have some freelance work avail?

merricksb• 9 years ago

This was heavily discussed 5 months ago:

https://news.ycombinator.com/item?id=12928526

Show HN: Qt binding for Go with support for all major operating systems

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