Re: speed of qt terminal

[sfeam <sf...@us...>]

On Friday, 26 June 2015 04:56:26 PM Tatsuro MATSUOKA wrote:
> In octave-maintainers ML, the tread "gnuplot graphics toolkit bugs" is open.
> http://octave.1599824.n4.nabble.com/gnuplot-graphics-toolkit-bugs-td4671157.html
> 
> 
> In the discussion there is a statement.(by Daniel J Sebald)
> 
> ***************************************************************************************
> >    It is now the fastest and most full-featured interactive terminal option. (for qt) 
> 
> except the speed.  Perhaps there is some hardware in which Qt can use, 
> say, OpenGL directly, but on my system that isn't the case.  Qt terminal 
> is drastically slower. 
> ***************************************************************************************
> 
> 
> I have built windows version of gnuplot 5.0 and 5.1 with qt terminal.
> For my PC "all.dem" speed of windows, wxt, qt terminals, the qt terminal is fastest.
> 
> Qt development toolkits (Qt 5.3) for gnuplot for windows build are prepared from source
> with configure option "-no-opengl".
> 
> To my understanding, gnuplot does not use opengl. Am I right?

The Qt libraries can use opengl if it is available at run time.
For some versions of Qt this can be controlled using the environmental
variable QT_GRAPHICSSYSTEM. I think the default is "native" rather than
"opengl", which tells the library to use whatever output layer is
expected to be fastest.

	Ethan



> 
> In other places Daniel state
> ***************************************************************************************
> For example, qt terminal uses QPixmap 
> 
> http://doc.qt.io/qt-5/qpixmap.html
> 
> which is a feature of Qt to handle display of images.  However, this is 
> at a very high level in which image elements are treated individually, 
> not as a whole image.  Consequently, the user will find that the Qt 
> terminal can be rather slow for large data sets.  x11 is very low level, 
> so is much faster.  Yet, wxt is fast as well.
> ***************************************************************************************
> 
> This thread is made from just curiosity.
> 
> Tatsuro 
> 
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