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48 lines
2.5 KiB
Plaintext
48 lines
2.5 KiB
Plaintext
The {{KW|_WIDTH (function)|_WIDTH}} function returns the width of an image handle or current write page.
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{{PageSyntax}}
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:''result&'' = {{KW|_WIDTH (function)|_WIDTH}}[({{Parameter|imageHandle&}})]
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{{PageDescription}}
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* If {{Parameter|imageHandle&}} is omitted, it's assumed to be the handle of the current [[SCREEN]] or write page.
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* To get the width of the current program [[SCREEN|screen]] window use zero for the handle value: wide& = _WIDTH(0)
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* If the image specified by {{Parameter|imageHandle&}} is in text only([[SCREEN]] 0) mode, the number of characters per row is returned.
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* If the image specified by {{Parameter|imageHandle&}} is in graphics mode, the number of pixels per row is returned.
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* If {{Parameter|imageHandle&}} is an invalid handle, then an [[ERROR Codes|invalid handle error]] is returned.
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* The maximum pixel coordinate of a program [[SCREEN|screen]] is one less than what the function returns.
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''Example:'' A SUB program that centers text in any graphic screen mode except text mode [[SCREEN (statement)|SCREEN]] 0 using '''QB64'''.
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{{CodeStart}}
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s& = {{Cl|_NEWIMAGE}}(800, 600, 256)
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SCREEN s&
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Align 15, 5, s&, "This text is centered on the screen!"
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SUB Align (Tcolor, Trow, mode&, txt$)
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center& = {{Cl|_WIDTH (function)|_WIDTH}} (mode&) \ 2 'returns pixels in graphic modes
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MaxCol = (center& \ 8) + 1 'screen text width = 8 pixels
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Tcol = MaxCol - ({{Cl|LEN}}(txt$) \ 2)
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{{Cl|COLOR}} Tcolor: {{Cl|LOCATE}} Trow, Tcol: {{Cl|PRINT}} txt$;
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END SUB
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{{CodeEnd}}
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: ''Explanation:'' [[_NEWIMAGE]] enlarges a screen to 800 pixels wide which is what [[_WIDTH (function)|_WIDTH]] will return. The center is 800 \ 2 or 400. Since the text width is 8 pixels, that is divided by 8 to get 50 as the center text column. Then half of the text length is subtracted to find the starting text print [[LOCATE]] column.
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: ''Note:'' The screen handle parameter is required because using no handle could assume other page handles created by functions like [[_NEWIMAGE]] or [[_PUTIMAGE]]! Use the correct handle in the SUB call! When using SCREEN 0, the MaxCol variable is not needed because _WIDTH returns the number of text columns, not pixels. Use the center value and add 1.
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<center>Tcol = (center& + 1) - LEN(txt$) \ 2 </center>
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{{PageSeeAlso}}
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* {{KW|_HEIGHT}}, {{KW|_LOADIMAGE}}, {{KW|_NEWIMAGE}}
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* {{KW|WIDTH}} (statement)
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* {{KW|Bitmaps}}
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{{PageNavigation}} |