[ColorWidget] Add CMYK support

[troopa81]

This is the first PR regarding CMYK QEP

It adds CMYK support in color widget so we can select CMYK color.

A new setting activeCmykComponent has been introduced, while the old one activeComponent refers now only to the Rgb/Hsv part

Funded by Métropôle de Bordeaux

[github-actions]

🪟 Windows builds ready!

Windows builds of this PR are available for testing here. Debug symbols for this build are available here.

(Built from commit 1ad2b4b)

[nyalldawson]

@troopa81 There's a fair amount of wasted space in the dialog caused by putting the combo box in the top left corner. Could we try moving it here instead?

How does this look in the vertical orientation mode used in the styling dock color buttons too? Can you share a screenshot showing that?

[nyalldawson]

Question: is the use of rounded integer 0-255 values an issue when using CMYK colors? It's been on my wishlist for a while to revisit these widgets and make them return qreal values for the color components, so that we aren't losing information when a color is changed via the widget and are better equipped to handle higher precision color models in future (since these are already supported by both Qt and our color reading/writing code, it's really only the color widget itself holding us back).

[troopa81]

Question: is the use of rounded integer 0-255 values an issue when using CMYK colors?

As much as RGB color I think. Do you have a specific issue in mind ? or just the lack of precision when you use the color wheel widget for instance

[troopa81]

@troopa81 There's a fair amount of wasted space in the dialog caused by putting the combo box in the top left corner. Could we try moving it here instead?

Way better indeed. Done and updated video accordingly

[spacehobo]

Question: is the use of rounded integer 0-255 values an issue when using CMYK colors?

As much as RGB color I think. Do you have a specific issue in mind ?

One reason to use CMYK is so that you can hit very specific spot colours used by your printers. This allows prints to get very high DPI at the tones you specify, because they don't need to use screens to dither various colours together.

If I can't specify the exact percentages from my printer's catalogue of spot colours, and have them propagate all the way through to a CMYK-colourspace PDF put out by the Layout Manager, then the result will be a very expensive print of a map with degraded quality.

[troopa81]

@nyalldawson I remoed the warning message

@spacehobo Good point, I'll try to deal with this in another PR if I have the time/budget.

[nyalldawson]

Just one little change left