Ctrls
To create a TempleOS graphic ctrl, you define callback functions and insert a 
CCtrl structure in the CTask queue.  See ::/Demo/Graphics/Slider.HC, 
::/Demo/Graphics/ScrollBars.HC and TermBttnNew.  There is a template-code ctrl 
generator, if you press <CTRL-SHIFT-L>.

CCtrl               Class class CCtrl
CViewAngles         Class class CViewAngles
CWinScroll          Class class CWinScroll
CtrlBttnDel         Funct Free bttn ctrl.
CtrlBttnNew         Funct Create bttn ctrl. See ::/Apps/Strut/Strut.HC.
CtrlFindUnique      Funct Find task ctrl given ctrl_type.
CtrlInside          Funct Is x,y inside a ctrl?
ViewAnglesDel       Funct Free view angle ctrl.
ViewAnglesNew       Funct Create view angle ctrl. See ::/Demo/Graphics/Shading.HC.