[Interest] Drawing slow.

[william.crocker at analog.com]

On 08/17/2018 02:36 PM, Bill Crocker wrote:
> Hello:
>
> My newer, Qt based drawing program takes orders of magnitude longer to draw lines
> than my good old plain X-Windows based drawing program.
>
> The Qt call stack, as revealed by VTune, is:
>
> QPainterPath::draw
> QPaintEngineEx::draw
> QRasterPaintEngine::stroke
> QPaintEngineEx::stroke
> QRasterPaintEngine::fill
> QRasterizer::rasterize
> QScanConverter::end
>

 From some experimentation it appears that the CPU time required by the
QPainterPath system is quite non-linear in the number of control points.
So, if I break my one long path up into a number of shorter paths, it
draws MUCH faster.

I use the QPainterPath because I have a dotted-line option and it knows
how to handle the corners.

Bill

> Am I using some fancy, expensive feature
> that I should turn off.
>
> Thanks.
>
> Bill
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