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Comment by walterbell | Hacker News Reader

Can QML/QtQuick work without a 3D-optimized gpu, e.g. in embedded?

Qt 5.8 includes a software renderer, but these days, most embedded platforms have a perfectly fine gpu.

I have used QML with good success in an embedded environment, although the embedded processor I was using did support OpenGL. If you want to use QML in even more constrained systems, it looks like there has been some work done on this [1], but I haven't tried it to see what the limitations are.

[1] http://blog.qt.io/blog/2015/01/22/introducing-the-qt-quick-2...

You'll need a processor beefy enough to run the Webkit javascript engine. There was talk a while back about V8 making it into Qt, but I haven't seen much about it recently.

I tried it once on a 400MHz MIPS core and it was awful. I'd say you need at least 800 to 1200 Mhz of ARMv7 core to make it look decent. Otherwise stick to 2D widgets.

They recently replaced Qt's v8 engine with a smaller self built one called v4, no?

I was under the impression that once the scene graph is set up, JS performance does not matter all that much, but then I'm running a rather modest application with JS being mostly used for bindings. What parts have been slow to you?

The whole thing was slow, mostly because I had way too little RAM (webengine consuming a large chunk of it), an underpowered CPU, and no 2D or 3D acceleration so it was all in raster mode.

Solving your problem with an embedded web browser probably would not have been good no matter which browser it was given your hardware constraints.

If you use QML, Qt uses the browser engine to execute the scripted part of QML/QtQuick. (Or at least it used to when I worked on this one particular project).

That's the core of the discussion here.

How would this work on, say, raspberry pi 2 which also has a powerful GPU?

You can easily get 60 FPS on a Pi 2 with Qt

>You'll need a processor beefy enough to run the Webkit javascript engine. There was talk a while back about V8 making it into Qt, but I haven't seen much about it recently.

How recently have you used Qt? Qt replaced WebKit with V8 in the 5.0 release, way back at the end of 2012. Since then they've developed a QML-optimized JavaScript engine called V4. It's slightly slower than V8 for some things, but significantly faster than V8 for the most frequent and critical QML use cases.

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