From QB64 Wiki
Revision as of 16:39, 5 June 2011 by imported>Clippy
Jump to navigation Jump to search

The _MOUSEWHEEL function returns a positive or negative INTEGER value indicating the mouse scroll wheel clicks since the last mouse read.


scroll% = _MOUSEWHEEL


  • Positive return value of 1 represents one "click" the mouse wheel was moved toward the user.
  • Negative return value of -1 represents one "click" the mouse wheel was moved away from the user.
  • After a "click" has been read, the value resets to 0 automatically.
  • If no movement on the wheel has occurred since the last _MOUSEINPUT read, _MOUSEWHEEL returns 0.
  • You may want to use a cumulative mouse wheel scroll value using a total variable.

Example 1: Reading the cumulative mouse wheel "clicks".

DO: _LIMIT 100 DO WHILE _MOUSEINPUT Scroll = Scroll + _MOUSEWHEEL LOCATE 10, 20: PRINT Scroll LOOP LOOP UNTIL INKEY$ = CHR$(13) ' press Enter to quit

Example 2: A simple text scrolling routine using the mouse wheel value to read a text array.

DIM Array$(100) LINE INPUT "Enter a file name with 100 or more lines of text: ", file$ OPEN file$ FOR INPUT AS #1 DO UNTIL EOF(1) inputcount = inputcount + 1 LINE INPUT #1, Array$(inputcount) IF inputcount = 100 THEN EXIT DO LOOP FOR n = 1 TO 21: PRINT Array$(n): NEXT CLOSE #1 DO DO WHILE _MOUSEINPUT IF row >= 0 THEN row = row + _MOUSEWHEEL ELSE row = 0 'prevent under scrolling IF row > inputcount - 20 THEN row = inputcount - 20 'prevent over scrolling IF prevrow <> row THEN 'look for a change in row value IF row > 0 AND row <= inputcount - 20 THEN CLS: LOCATE 2, 1 FOR n = row TO row + 20 PRINT Array$(n) NEXT END IF END IF prevrow = row 'store previous row value LOOP LOOP UNTIL INKEY$ > ""

Code by Ted Weissgerber
Note: QB64 comes with a text file called readme.txt that is large enough for this example.

See also

Keyword Reference - Alphabetical
Keyword Reference - By Usage
Main Wiki Page