[Interest] Qt Quick Controls 1 deprecated but no native styles for Qt Quick Controls 2?

[Giuseppe D'Angelo]

Hi,

Not a real answer to the Qt Project's direction, just a few pointers.

Il 07/12/18 10:09, Dimitar Dobrev via Interest ha scritto:
> The release notes for Qt 5.12 
> <https://wiki.qt.io/New_Features_in_Qt_5.12> worry me quite a little. 
> They say that Qt Quick Controls 1 is deprecated. There's a single but 
> key reason this is extremely bad news. And this reason is the lack of 
> native styles in Qt Quick Controls 2. This alone renders Qt Quick 
> Controls 2 useless for building decent desktop applications. 

Note that this isn't necessarily true in general, e.g. take a look at 
Electron-based desktop applications, which deliberately not follow any 
native style. (I'm not saying that this is good or bad; I'm just saying 
that those applications exist). QQC2 would be a good match for such 
usecases.


> This in 
> turn means our only option remains Qt Widgets - a piece of technology 
> which is like a horse carriage. Good for its time but useless in the era 
> of automobiles. The very notion of suggesting that for desktop 
> development in 2018 we would be deprived of a simple declarative 
> language for GUI, a flexible scripting language to match, GPU-based 
> optimizations and all other wonderful features Qt Quick has to offer - 
> is ridiculous at best. 

A few technical notes:

1) You can define QWidget based hiearchies using QML , see for instance

> https://github.com/KDAB/DeclarativeWidgets

2) At the very core of native styling in Qt there's QStyle, which uses 
CPU-based rendering, relying on pixel perfect output provided by 
QPainter. (Take a look into a style class, you'll found thousands of 
QPainter draw calls). A native style built for QQC2 will mean one of 
these options:

* re-using QStyle existing code, which means neglecting your GPU-based 
optimizations

* reimplementing native styles just for QQ2 using GPU-accelerated 
primitives, which is super-difficult and surely an investment noone 
wants to make (not to mention it would mean two implementations of 
native styles, who is going to maintain those?)

* port QStyle itself to some abstraction that allows for GPU-accelerated 
rendering (and of course keep CPU-based rendering around, for GPU-less 
environments) which again sounds extremely hard, risks regression all 
over the place, it's probably a Qt 6-worth break, etc.


> If it's true that Qt Quick Controls 1 is 
> deprecated and Qt Quick Controls 2 won't get native styles any time 
> soon, this simply means Qt has severely regressed in its offerings to 
> developers.

Why do you say "won't get native styles"? (What I mean is, where does 
this certainty for the future come from?)


-- 
Giuseppe D'Angelo | giuseppe.dangelo at kdab.com | Senior Software Engineer
KDAB (France) S.A.S., a KDAB Group company
Tel. France +33 (0)4 90 84 08 53, http://www.kdab.com
KDAB - The Qt, C++ and OpenGL Experts


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