Bug 369268

When using krita and drawing I usually change the size of my tool frequently to add details as well as ad new sections to my image. Having to click and resize the tool using the toolbar at the top is usually too tedious and time consuming so I prefer pressing shift and moving my pen (whilst pressing on the canvas as if to draw) up to size up or down to size down the tool I'm currently using. This feature worked flawlessly in the last version but now when I use them there is a brief moment between sizing it in which the program seemingly lags or freezes leaving me with the incorrect size I require.  It seems to lag more as the tool is smaller and sometimes I need to up size it to a huge scale in order to make sure its responding.

Reproducible: Always

Steps to Reproduce:
1. Press Shift+Press cursor against canvas
2. whilst pressing move up/down to resize tool
3. Move in small quantities to see the issue happen more frequently

Actual Results:  
There is a noticeable lag that hinders the fluency of the program. Hinders the ability to size up or down tools using the keyboard shortcut.

Expected Results:  
No lags or freezes, just simple change in the tools size.