Add fan speed visualization in preview

[jschuh]

This adds an option to preview fan speed as requested in issue #1491.
I needed this to verify that patch #2921 generates correct output.

[jschuh]

Checkout was in a messed up state when I uploaded this, so I have a to fix a few things and then I'll re-post it.

[jschuh]

Seems correct now. Sorry for the noise. I'm just learning Github's workflow (and am far from an expert on git in general).

[bubnikv]

thanks, merged into master.
I may refactor the fan speed and color change ID away from ExtrusionPath into either a separate structure just for the final G-code preview, or for the same, but derived from ExtrusionPath.

[jschuh]

Thanks, glad it was useful.

[rongith]

@jschuh, in the function void GCodeAnalyzer::_processM106(const GCodeReader::GCodeLine& line) I would set
_set_fan_speed((100.0f / 255.0f) * new_fan_speed);
then 100% fan speed is 100 and not 99.609375

[jschuh]

Sorry, been busy with other things for the last few months. Answer inline...

@jschuh, in the function void GCodeAnalyzer::_processM106(const GCodeReader::GCodeLine& line) I would set
_set_fan_speed((100.0f / 255.0f) * new_fan_speed);
then 100% fan speed is 100 and not 99.609375

Ah, that is a bug. The divisor should be 255 rather than 256, otherwise the percentage is off by a small fraction. However, the float promotion is implicit, so you don't need to change the type of the divisor (unless you just think it's clearer code).

Unfortunately, I don't have a functional checkout right now, but it's a very simple patch if you want to submit it as a PR. Otherwise, I'll circle back to it once I get a chance.

[rongith]

@jschuh, I just changed a 6 to a 5 and Prusa already committed it. Perhaps someone with extra super high color sensitivity could have been annoyed.... It is more about perfection.

[jschuh]

@rongith, that's awesome. Thanks for getting it fixed.