Set the amount argument passed by arrow Timer notifications to

Prop_Increase and Prop_Decrease. Default one.

ULONG; initialize, set and get. Getter writes the stored amount to IPTR

storage.

Setting rebuilds each existing arrow Timer notification: KillNotify

removes notifications for Timer, then a new increase/decrease

notification is registered. Results are ignored. Zero and large amounts

are accepted without validation. Prop applies its own deltafactor and

bounds; the amount is not an unconditional pixel count. In border mode

there are no arrow Image objects, so this attribute is stored but does

not configure the window arrow gadgets.

A getter value confirms stored state, not successful notification

registration. Prop arithmetic can overflow for large amount/factor

combinations; no extra validation is provided here.

Choose the ordering of Prop and arrow children. Default is

MUIV_Scrollbar_Type_Default.

LONG; initialize only. Use Default, Top, Bottom or Sym.

Top initially orders Prop, decrease arrow, increase arrow. Bottom orders

decrease arrow, increase arrow, Prop. Sym orders decrease arrow, Prop,

increase arrow. Default initially uses Top order, then Setup applies the

application arrangement preference. Explicit types bypass that

preference reorder. These are actual list orders; names must not be

interpreted as a different visual ordering. With Prop_UseWinBorder, only

Prop is attached and this order is irrelevant. No local setter or getter

exists.

Values outside the four enum constants are not rejected and select no

insertion branch outside border mode. Created objects can remain

unattached and undisposed.

Group.mui

Combine a Prop child with decrease/increase arrow Images. Group_Horiz

chooses orientation at construction; default FALSE is vertical. Without

Prop_UseWinBorder, arrows use Timer notifications to call

Prop_Decrease/Increase. With a nonzero border selector, only the Prop is

attached and the Scrollbar receives the border-gadget flag.

Attached Prop/arrows are Group-owned. Scrollbar has no local disposer;

normal Group lifecycle and disposal apply. Use Prop_First, Prop_Entries

and Prop_Visible through Group forwarding to control the range. There is

no separate public Prop-child getter.

Construction creates Prop before Group and temporarily changes the first

caller ShowMe tag to TAG_IGNORE while creating Prop, then restores it.

The tag list must be writable. Additional repeated ShowMe tags are not

filtered by that single FindTagItem operation.

Setup calls Group first. For Type Default outside a window border, it

reorders the three children according to the application's scrollbar

arrangement. Its scrollbar-style preference switch currently makes no

changes. Setup returns FALSE on Group failure and TRUE otherwise,

ignoring sort results. Do not add unrelated children: the default sort

enumerates only the three internal objects.

If Group construction fails, the already created Prop is not explicitly

disposed here. Prop and arrow allocation failures are not safely

rejected before Group addition, whose helper expects non-NULL children.

An unsupported Type leaves created objects unattached because the

insertion switch has no default branch. Thus a non-NULL result is not

proof of a complete usable control.

Forwarding and child-get fallback are inherited from Group; they are not

independent storage for Prop attributes. Keep the internal children and

their notification targets intact.