_MOUSEWHEEL

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

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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$(n) NEXT END IF END IF prevrow = row 'store previous row value LOOP LOOP UNTIL INKEY$ > ""

Example by Ted Weissgerber

See also

• Featured in our "Keyword of the Day" series
• _MOUSEX, _MOUSEY, _MOUSEBUTTON
• _MOUSEINPUT, _MOUSEMOVE
• _MOUSESHOW, _MOUSEHIDE
• Controller Devices

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