Spectrum fill/gradient

[srcejon]

This PR adds support for drawing the spectrum as filled (including max hold) or with a gradient using the colour map. The colour map is now also applied to 2D waterfall.

Note, I've added a combo to select between Line / Fill / Gradient. However, you might want to change this logic so that it switches between Line / Fill / Gradient / Phosphor effect - as the phosphor effect doesn't work well with the filled spectrum. Icons might be nicer/more compact than words too - you do a better job of making those!

Any idea why the m_waterfallPalette is only 240 entries? I haven't tried to expand that - but all of the Color Maps I've added are 256 entries - so it possibly could be.

[f4exb]

you do a better job of making those!

Thanks! Yes don't worry I will re-arrange this and probably split the first line into sub sections as it is growing too big.

Any idea why the m_waterfallPalette is only 240 entries

Well this is very old code probably from the early SDRangelove. I have to inspect the code to retrieve the logic (or not logic).

[f4exb]

the phosphor effect doesn't work well with the filled spectrum

I think it's OK (maybe a video would render the effects better...):

Note: I have started re-organizing the icons a little bit.

[srcejon]

Yeah - having another look, some colour schemes work OK (if max hold is switched off). Looking good.