Difference between revisions of "MOUSEWHEEL"

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The '''_MOUSEWHEEL''' function returns a positive or negative {{KW|INTEGER}} value indicating the mouse scroll wheel clicks since the last mouse read.
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{{DISPLAYTITLE:_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]].
  
  
 
{{PageSyntax}}
 
{{PageSyntax}}
:{{Parameter|scroll%}} = {{KW|_MOUSEWHEEL}}
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: {{Parameter|scrollAmount%}} = [[_MOUSEWHEEL]]
  
  
 
{{PageDescription}}
 
{{PageDescription}}
* Positive return value of 1 represents one "click" the mouse wheel was moved toward the user.
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* Returns -1 when scrolling up and 1 when scrolling down with 0 indicating no movement since last read.
* Negative return value of -1 represents one "click" the mouse wheel was moved away from the user.
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* After an event has been read, the value resets to 0 automatically so cumulative position values must be added.
* After a "click" has been read, the value resets to 0 automatically.
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* If no movement on the wheel has occurred since the last [[_MOUSEINPUT]] read, [[_MOUSEWHEEL]] returns 0.
* If no movement on the wheel has occurred since the last {{KW|_MOUSEINPUT}} read, _MOUSEWHEEL returns 0.
 
* You may want to use a cumulative mouse wheel scroll value using a total variable.
 
  
  
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{{PageExamples}}
 
''Example 1:'' Reading the cumulative mouse wheel "clicks".
 
''Example 1:'' Reading the cumulative mouse wheel "clicks".
 
{{CodeStart}} '' ''
 
{{CodeStart}} '' ''
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{{CodeEnd}}
 
{{CodeEnd}}
 
{{small|Code by Ted Weissgerber}}
 
{{small|Code by Ted Weissgerber}}
<center>Note: QB64 comes with a text file called ''readme.txt'' that is large enough for this example.</center>
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<center>Note: You will need a text file that is large enough for this example.</center>
  
  
 
{{PageSeeAlso}}
 
{{PageSeeAlso}}
*{{KW|_MOUSEX}}, {{KW|_MOUSEY}}, {{KW|_MOUSEBUTTON}}
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* [[_MOUSEX]], [[_MOUSEY]], [[_MOUSEBUTTON]]
*{{KW|_MOUSEINPUT}}
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* [[_MOUSEINPUT]], [[_MOUSEMOVE]]
*{{KW|_MOUSESHOW}}, {{KW|_MOUSEHIDE}}
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* [[_MOUSESHOW]], [[_MOUSEHIDE]]
*{{KW|DECLARE LIBRARY|MouseMove}} (SDL library function)
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* [[Controller Devices]]
  
  
 
{{PageNavigation}}
 
{{PageNavigation}}

Latest revision as of 17:46, 9 September 2017

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.


Examples

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: You will need a text file that is large enough for this example.


See also



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