Scrolling

Make the unit scrolling increments (for example, the smallest amount a scrolled area can be scrolled when using an associated scroll bar) equal to those shown in Table 1-11 “Scrolling Increments”

When the user presses PageUp or PageDown and focus is on a scrollable area, scroll up or down by one page.

When the user presses PageLeft (or Ctrl PageUp) or PageRight (or Ctrl PageDown) and focus is on a scrollable area, scroll left or right by one page.

When the user is using the paging keys to scroll (and ScrollLock is not used), move the active cursor within the scrollable area so that it is visible, unless the cursor cannot be placed in the visible area after scrolling.

Paging keys should apply to the most deeply nested appropriate scrollable area that contains the active cursor.

If a scrolled control (for example, a text field) maintains a cursor location even when it does not have focus, then when keyboard navigation is used to move focus to that control, scroll it, if necessary, so that the cursor location is visible.

When the user navigates to an element within a scrollable area, scroll the area so that the element is visible.

When any keyboard operation moves the cursor within a scrolled control, or inserts, deletes, or modifies elements at the cursor position, scroll the control so that the cursor is visible when the operation is complete.

Design navigation operations to traverse through an entire scrollable area, not just the visible portion of it.

If the user can change the size of a scrollable control or area, and the cursor is visible in that area, scroll it so that the cursor remains visible.

When the user scrolls with a mouse, do not move the cursor in the underlying data; instead, allow it to be scrolled outside of the visible area.

If the active cursor is within a scrolled area, but is not visible, indicate focus emphasis by placing an element cursor on the entire scrolled area.

When the user presses Cancel (or Esc), cancel the mouse-based scrolling action and return the scrolling area to its position prior to the start of the scrolling operation.

When a mouse-based selection operation is in progress within a control that supports scrolling and the user moves the pointer outside of the control, scroll towards the pointer. This is called "selection autoscrolling."