A basic Question

Eeli K

Just one stylistic note... Quick Controls 2 standard library qml code uses this extensively so it may be at least good to know even if you don't want to use it. It's alternative syntax for nested if-else. Modifying my own code, just set the rectangle color (or in sierzio's code the image source):

color: root.isConnected ? (mouseArea.containsMouse ? "red" : "green") :
       (mouseArea.containsMouse ? "blue" : "yellow")

This is from the Material style's Button.qml:

color: !control.enabled ? control.Material.hintTextColor :
            control.flat && control.highlighted ? control.Material.accentColor :
            control.highlighted ? control.Material.primaryHighlightedTextColor : control.Material.foreground

sierdzio

Heh, actually the first version of my snipped used the question mark notation, but I changed it to if-else because I thought it would be more readable.

It is definitely a good approach, and for simple cases I would recommend it - QML engine can optimize the question mark operator more heavily than if-else.

mrjj

hi
oh my gosh, is that like a c++ ternary operator that can be nested ?
But its not super readable unless really short.

GrecKo

It's the same, a c++ ternary operator can be nested.

mrjj

@GrecKo
Yep, i realized that after asking but I think i never saw one in c++
like
!m_seedsfilter ? good=true : m_seedsfilter==1 ? good=newClusters(Sp) : good=newSeed(Sp);

(ugly as hell)

GrecKo

Off-topic but it would be good = !m_seedsfilter? true : m_seedsfilter == 1 ? newClusters(Sp) : newSeed(Sp);, it's the same notation in Js and in c++

mrjj

Thanks
but was just live sample from
https://stackoverflow.com/questions/18237432/how-to-rewrite-complicated-lines-of-c-code-nested-ternary-operator/18237507
But back to topic a bit.

Do you know how much of JS that is supported in QML ?
Can i include .js stuff ?

sierdzio

@mrjj said in A basic Question:

Do you know how much of JS that is supported in QML ?
Can i include .js stuff ?

I think V4 engine implements full ECMA 5.1 specs, so you can run any JavaScript there, unless it uses newer features.

mrjj

@sierdzio said in A basic Question:

ECMA 5.1 specs

so that is pretty old ?
5.1 Edition / June 2011
https://www.ecma-international.org/ecma-262/5.1/

So most from
https://www.javascripting.com/

might not work as 6 years in Web tech is a decade ?

sierdzio

It is old, indeed. But a lot of projects like node.js, charts.js etc. seem to be working (or used to work 1-2 years back).

There is a ticket for upgrading the engine, but it lays dormant since years https://bugreports.qt.io/browse/QTBUG-47735

mrjj

@sierdzio

Ok sounds pretty good. even if older.

It is odd that its not been updated since lots of activities on QML.

Thank you for all the info :)

sierdzio

@mrjj said in A basic Question:

It is odd that its not been updated since lots of activities on QML.

There was a discussion about it on the mailing list once. If I recall it correctly, the priority for Qt devs working on QML was to keep the engine fast, and make it work 100% reliable in common QML use cases (and the most common uses are: small bindings/ assignments and short functions) - so they did not feel pressure to implement newer features.