Gerald Young authored Oct 17, 2014 and Dmitry Kazakov committed Oct 17, 2014

The issue was two fold. Firstly on krita/ui/tool/kis_tool_freehand.cc
didn't respond well to slow dragging motions. The brush size can only
increment in integer pixel values, but a slow dragging motion generates
increments smaller than one pixel. These small increments get truncated
once passed to brush settings and the drag motion is discarded. Solution
was to accumulate the drag motion until it is higher than one pixel.

A second problem was that KisDoubleSliderSpinBox would implicitly convert
the provided qreal to an int value. This conversion works like the floor
function, for example turning a 0.1 into a 0 value (ok) and
turning a -0.1 value into a -1 value (not ok). This was the cause of the
weird behavior where brush size would decrease even when dragging right
slowly. Solution was to use qRound to avoid the implicit conversion.

BUG:339870
REVIEW:120610

Thanks Gerald Young for the patch! :)