Improving Performace

[Snolandia]

Just wanted to start a discussion on this to keep track of what I'm finding/ trying to improve, and for suggestions/solutions.

This push started because while using the live-data sample graph, while the performance for 1 graph was ok enough for my uses,
while trying to add multiple graphs performance was significantly poorer than will meet my needs, as well as running into a weird rendering bug seemingly caused by the performance drop.

[Snolandia]

JKQTPEnhancedPainter, drawPolyLineFast

Im finding that QPainter drawPolyline has some signifigant performace issues. Just by moving to a loop and using QPainter::drawLine, Ive seen an average of 250% speed increase in drawing lines. Continuing to dig into this.

[jkriege2]

Yes, it might be a good idea to add functions that enable a mode where drawPolylineFast() is forced (if you'r OK with the reduced quality) ... that may be implemented alongside setUseAntiAliasingForGraphs() ...

[jkriege2]

image caching is something I wanted to implement at some point (do go ahead, if you want to!) ...

text is - performance-wise - a weak point of JKQTPlotter: By using JKQTMathText it can draw using LaTeX markup, but also slows down the drawing .... but I decided FOR the plot quality, as performance was sufficient for me ...

[Snolandia]

image caching is something I wanted to implement at some point (do go ahead, if you want to!) ...

text is - performance-wise - a weak point of JKQTPlotter: By using JKQTMathText it can draw using LaTeX markup, but also slows down the drawing .... but I decided FOR the plot quality, as performance was sufficient for me ...

Glad for the quality. For some tables I made, I spent way to long trying to get QPainter to draw text vertically correctly before I ended up just making it draw on a pixmap and rotated that.

The image caching will probably take me a bit to set up as there is quite a lot of stuff intertwined to go through and finding the spare time to do it.

[Snolandia]

Yes, it might be a good idea to add functions that enable a mode where drawPolylineFast() is forced (if you'r OK with the reduced quality) ... that may be implemented alongside setUseAntiAliasingForGraphs() ...

And as far as I could tell, there was no visual difference between drawPolylineFast, and drawLines. Though I didnt do any extensive testing.

[jkriege2]

One more thing about caching: there is some caching of text already ... there is already some caching for text drawing: not on the drawing itself, but for the size calculation. This is implemented in the get Mathtext Size functions in JKQTBasePlotter ...

This refines the need to parse the latex markup again and again and to recalculate the sizes of e.g. axis labels that do not change much between frames ...

[Snolandia]

Setting up SetX, SetY, and SetXY to have a No-ReDraw overload option, and using that when updating the multiple axis/datapoints then calling redraw at the end of everything significantly improved performance by nearly double for the live graph example, which setX then redrew the plot. framerate went from 30fps to about 60fps, based off a QTimer::singleshot set to 10ms after every frame update.

[jkriege2]

This is possible ... but it's not well documented:
Plotting is controlled via signals. There if you call JKQTPlotter::setPlotUpdateEnabled(false) before setting up the plot, redrawing is disabled and JJKQTPlotter::setPlotUpdateEnabled((true) reenables it. You may have to call redrawPlot() afterwards to update the display!

I just added a guard class JKQTPlotterUpdateGuard that automates this and improved the documentation about this topic!

[Snolandia]

Oh shoot. I totally missed that and going back and looking I see the function for it. Woooops.

[zhangxiaoGreen]

I want to generate a line Graph which has no more than 1000 line every line has 512 points. is this be supported