show R-G-B color bars in SpectralView plot widget for quickly changing raster layer renderer bands

[Andreas Janz]

Discussed with Tobias Hank and in #700.

Add a mapLayerComboBox in the SpectralView visualisation settings for selecting a raster layer.

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Show the RGB/Gray renderer bands of the selected raster layer as bars inside the plot widget:

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The RGB bars are freely movable via drag&drop, which will update the renderer.

Implement default behaviour: when the creation of a new SpectralView is triggered by showing a raster layer pixel profile, directly use that raster layer and show the renderer bands.

[Andreas Janz]

First prototyp works. RGB bars can be moved via the BandComboBoxes.

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[Andreas Janz]

Bars can now be dragged around inside the plot.

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[Andreas Janz]

resolves #837

→ <<cset 8a06f371ced0>>

[Agustin Lobo]

I do not have the Renderer Bands in 3.9

[Agustin Lobo]

Works nicely with 3.10 dev

Just:

1. why the Band Index and Band Number go up to 2000 (instead of actual max)?
2. why does the x start at 0 (instead of actual min) for wavelength?

This is wasting space in the plot and makes the user change it every time.

Also:

1. 5 decimal places by default is way too much.
2. I would prefer seeing the band number along x in nm, something like x: 1750 (b 200) y: 419.6

Otherwise I need to be changing the axis over an over

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[Andreas Janz]

why the Band Index and Band Number go up to 2000 (instead of actual max)?

Yes, that should be fixed, see #893.

[Andreas Janz]

why does the x start at 0 (instead of actual min) for wavelength?

That is a known issue, that is even more critical for temporal plots, see #851

[Andreas Janz]

5 decimal places by default is way too much.

I guess you are refering to this cursor information here, right?

I would prefer seeing the band number along x in nm, something like x: 1750 (b 200) y: 419.6

I agree, showing information of an actual profile data point would be the much more relevant. The current cursor location info is kind of useful, but not very.

See #894.