Bug 313202

N.B. Allowing Ctrl+Click to pick colours from the current layer might appear to duplicate functionality from bug 313308. However there are differences which I believe makes both options potentially useful:
Switch via options docker for Ctrl+Click:
When I select colours from a single layer, it is usually because I'm (e.g.) working on blending colours within the layer. This means switching to picking from the current layer repeatedly for a while. To my mind the solution of being able to change the behaviour via an options docker (and being able to assign a shortcut to switch), then continue using the same shortcut (Ctrl+Click) for picking is the best solution for this use-case. I have ctrl set as one of the tablet's buttons; I don't have a spare button to add ctrl+alt.

bug 313308: A one-off single-layer colour picking. Very useful for occasional use (When fiddling with options and having to reset them afterwards would be a nuisance), but not suited to the use-case described above.

Additionally, could make Ctrl+Alt  reverse the behaviour, so when Ctrl+Alt is set to current layer, Ctrl+Alt can be used for one-off colour picking from all visible layers.

Does that make sense?

+1 for :

Ctrl+Click (with freehand painting)   = the color picking setting as on the color picking tool option 

and Ctrl+Alt+Click (with freehand painting)  = the inverse of the color picking setting as on the color picking tool option

Ack -- this would be good to implement.

Finally my opinion changed with time using Dmitry fix done , the one T Hall linked ( https://bugs.kde.org/show_bug.cgi?id=313308 ). So my comment #2 not reflect my actual thinking. 

To resume , now on master :
>> Ctrl+click --> Pick color all sample merged
>> Ctrl+Alt+click --> Pick color of active layer
...witch work fine for me, especially working on blending mode layer. 

So, now only the color picker radius is missing. Personnaly I like to leave it to 1px as default.

David,
As I envisaged it, the current situation (Ctrl+click --> Pick color all sample merged, Ctrl+Alt+click --> Pick color of active layer) would still be the default. All that would change would be to allow the user to flip the actions via a setting in the colour picker options.

Most of the time, the current behaviour is best, but occasionally, I find myself doing something such as blending colours on a layer with a different blending mode (e.g. multiply). In this case, it would be more convenient to reverse the behaviour (So that Ctrl = active layer, Ctrl+Alt = sample merged) for the duration of the blending work, then switch it back, rather than having to use Ctrl+Alt every time (More buttons to press, no room for Alt-key on tablet buttons, and I'll keep absent-mindedly pressing Ctrl instead and getting the wrong colour). Those who just want to use the default (un-reversed) behaviour needn't even know the possibility were there.

WISHGROUP: Small Usability Fixes

I think in recent version of Krita the radius is now taken into consideration while ctrl color picking like deevad requested in comment #4. The option to toggle or interchange the default behavior of ctrl + click <-> ctrl + alt + click is still remaining to be implemented

Note: I would actually want to add more modes into color picker. For example pick color from color labeled layers or pick color from the current layer and all below. It's useful when working with files with filter layers or just effects on top of the main image. 

So maybe it would be a good idea to have a separate shortcut-able action "pick color using the current color picker options" (since people might be already used to cltr+pick picking always from the current layer etc.). 

For that, adding an option "Update color as (o)Foreground/( )Background" to the tool options would be useful.