KnobEventHandler motion event handling broken when using log scale

[sboettner]

If you set a knob to use a logarithmic scale, manipulating the knob value by clicking and dragging the mouse on the knob does not work correctly: The value remains on the minimum value or something very close to it. Changing the value using the mouse wheel works correctly.

Can be reproduced with the CairoUI example by inserting the following lines in the constructor:

fKnob->setRange(1.0f, 100.0f);
fKnob->setUsingLogScale(true);

[falkTX]

thanks for the report.
it is likely a regression from the recent changes to fix integer behaviour

[joshsteffen]

I just ran into this and it looks like this commit got rid of some calls to invlogscale().

Adding a matching call to invlogscale() just above this seems to have fixed it, though I'm not familiar enough with the code to be confident that it's the Right Thing to do:

DPF/dgl/src/EventHandlers.cpp

Lines 446 to 450 in f581516

	const float divisor = (ev.mod & kModifierControl) ? accel * 10.f : accel;
	valueTmp += (maximum - minimum) / divisor * static_cast<float>(movDiff);
	if (usingLog)
	valueTmp = logscale(valueTmp);