While the button was held the Detail view drew one hard tinted circle per
pointer sample, so a fast stroke showed separate dabs; the committed stroke
interpolates dabs a quarter radius apart with feather and flow. The live
stroke now uses the pipeline's dab placement (push_dabs, shared with
brush_dabs), dab falloff and flow accumulation in an incremental screen
buffer (crates/ui-egui/src/brush_live.rs): each frame stamps only the new
samples' dabs and uploads only the rectangle they touched. push_dabs also
caps the dabs of a hostile segment instead of looping without bound.
Jason Baldwin
923b1cde5e