Cannot reproduce in Xubuntu 12.10 (Xfce 4.10)

Cannot reproduce in Debian testing/Wheezy (Gnome 3.4), although the picker is broken in a different way there: see bug #20311

Another workaround: press the keyboard shortcut for it, which by default is "R".

Reproduced this under Unity on an up-to-date Ubuntu 12.10 under Virtualbox, but it doesn't happen every time. PPA version
1.0.0+git20121125.4bc72ec-1ppa1~quantal1

I cannot reproduce this in Xfce 4.8 under Debian testing, nor Xfce 4.8 under Ubuntu 11.10. This is probably a Unity problem.

It seems to be limited to the pointer button colour picker, which in this PPA build is bound to both <Control>Button1 and <Alt>Button1 by default. It doesn't seem to be happening on the same action accessed via the keyboard mapping (the R key by default), but that way of getting at it is broken too.

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Symptom 1: colour picker does not continuously pick

Steps to reproduce

• Start MyPaint. Point the mouse at the canvas area.
• Hold down "R" and move the mouse
• Release "R"

Expected behaviour:

• Colour picker square and mouse cursor appear
• While the mouse is moved with "R" held, square and brush colour updates continuously with the colour under the cursor
• When the "R" key is released, square disappears and cursor changes back to the "brush circle"

Observed behaviour:

• Colour picker square and mouse cursor appear [correct]
• An initial update of the colour happens, but the colour in the queare and the brush coluur do not update continuously [incorrect]
• When the "R" key is released, square disappears and cursor changes back to the "brush circle" [correct]

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Symptom 2: colour picker square does not disappear when launched with mouse button combination

Steps to reproduce

• Start MyPaint. Point the mouse at the canvas area.
• Hold down <Ctrl>Button1 and move the mouse
• Release <Ctrl>Button1

Expected behaviour:

• Colour picker square and mouse cursor appear
• (picking happens: see expectations for symptom 1 but we're ignoring that here)
• When the combination is released, square disappears and cursor changes back to the "brush circle"
• Painting is now possible with the changed colour

Observed behaviour:

• Colour picker square and mouse cursor appear [correct]
• (picking happens, incorrectly: see observed for symptom 1 but we're ignoring that here)
• When the combination is released, square does not disappear and cursor does not change back to the "brush circle" [incorrect]
• Painting is now possible with the changed colour [correct]
• Moving the pointer over the picker square exits the popup state [workaround]

Quick addendum:
Bug is non-existant on the same tablet pc when running Arch with Gnome-Shell 3.4.2

Not sure if it is something with Ubuntu patched GTK, Compiz or a conflict with one of the dependencies.

While picking color using eyedropper the square overlay which display the color picked dosen't disappeared and the brush stays as eydropper icon even after selecting different brush. I have attached the image below please have a look at it