binary1248/SFGUI — comment on commit 133d53a7d6ba3c08a3d9bec46054fdf6664e332c
File: include/SFGUI/Widget.hpp line 148
By binary1248:

HandleSizeAllocate was used for general repositioning, allocation change, and handling invalidation etc. Instead of making widgets go through expensive size recalculation every time something small like (absolute) position changes, I split it up into HandleSizeAllocate which doesn't get called when the allocation doesn't really change and HandleAbsolutePositionChange when a parent knows it's position changed and needs to update it's children although their allocations didn't change at all (relatively seen). Simply put this is a way of saving unneeded placement recalculations etc.