_MOUSEWHEEL
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The _MOUSEWHEEL function returns a positive or negative INTEGER value indicating mouse scroll events since the last read of _MOUSEINPUT.
Syntax
- scrollAmount% = _MOUSEWHEEL
Description
- Returns -1 when scrolling up and 1 when scrolling down with 0 indicating no movement since last read.
- After an event has been read, the value resets to 0 automatically so cumulative position values must be added.
- If no movement on the wheel has occurred since the last _MOUSEINPUT read, _MOUSEWHEEL returns 0.
Availability
v0.851
all
yes
yes
yes
- Available for macOS since QB64-PE v3.13.0
Examples
- Example 1
- Reading the cumulative mouse wheel "clicks".
DO _LIMIT 50 DO WHILE _MOUSEINPUT Scroll = Scroll + _MOUSEWHEEL LOCATE 10, 20: PRINT Scroll LOOP LOOP UNTIL INKEY$ = CHR$(13) ' press Enter to quit |
- Example 2
- A simple text scrolling routine using the mouse wheel value to read a text array.
- You will need a text file that is large enough for this example.
DIM Array$(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$(n) NEXT END IF END IF prevrow = row 'store previous row value LOOP LOOP UNTIL INKEY$ > "" |
See also
- Featured in our "Keyword of the Day" series
- _MOUSEX, _MOUSEY, _MOUSEBUTTON
- _MOUSEINPUT, _MOUSEMOVE
- _MOUSESHOW, _MOUSEHIDE
- Controller Devices