a point a certain number of lines/characters within said edge). The view within a WYSIWYG word processor, for example, may scroll the whole viewport a certain amount down the page as the caret nears the lower edge of the edit window. This keeps the text currently being entered or edited roughly centered without excessive, distracting, and potentially computationally expensive line-by-line scrolling. A spreadsheet character-based word processor on a low-resolution screen may similarly scroll in all directions, character-by-character or line-by-line, maintaining a small margin which the caret never enters in order to show the user what text or cells lie directly ‘ahead’ of or ‘behind’ the edit point and prevent them from ‘working blind’. A plain text text entry form, by contrast, may use a simpler method, setting a fixed and arbitrary display width within which the caret always ‘wraps around’, only scrolling up or down a line as the caret reaches the wrap point at the start/end of the current first/last line, in order to keep the edit point in view as it moves to the previous/next line of text. All other scrolling must be manually controlled by the user by use of scroll bars, mouse wheel, or Page Up/Page Down keys. Another alternate form of control is used in some spreadsheets when the Scroll Lock key is activated. In this case the caret is locked to the centre of the screen and the cursor keys instead move the worksheet itself ‘underneath’ the static caret, instead of the caret moving ‘over’ the sheet. The margins that trigger a scrolling action are effectively increased to their maximum possible size (vs the minimum possible with the web edit box), causing the caret to be re-centered any time it attempts to move. See also Cursor (user interface) Spatial navigation Tabbing navigation Notes External links Mozilla/Gecko Keyboard Navigation Proposal User interface techniques Text editor features