Qwt Performance

[liran ritkop]

Hi all!!
I am using The Qwt Histograms chart in my project. The project is running on omapl138 (ARM cpu). I use Qt 4.7 and Qwt 6.0 , both cross-compiled.
What i have is a QwtPlot with canvas and grid and axes. On this QwtPlot i attach 3 QwtPlotHistogram objects, with 50 samples each. So, I have 50 bars for each histogram, therfore having 150 bars.
The problem is, that when i want to use QwtPlotZoomer on the canvas, it is way too slowly!! Also, when i want to go back to the 100% view, its replot too slow. When i have other Qt Object moving in the screen it moves slow too.
How should i implement a fast bars chart with 150 bars? what can i do?

[Uwe]

The problem is, that when i want to use QwtPlotZoomer on the canvas, it is way too slowly!! Also, when i want to go back to the 100% view, its replot too slow. When i have other Qt Object moving in the screen it moves slow too.

This is not enough information to be sure, but it sounds like you are having a slow graphics system - maybe using a unaccelerated framebuffer device.

I recommend to check the performance of your environment with a small Qt test application with one widget, that paints its background in a solid color for each paint event.

You could also use the refreshtest example of Qwt ( reduce the number of curve points to 1 ). But because of the panel on the left side of the application only a part of the screen is repainted and you might see a higher refresh rate as for fullscreen repaints.

Uwe