The [[PCOPY]] statement copies one source screen page to a destination page in memory. 


{{PageSyntax}}
: [[PCOPY]] {{Parameter|sourcePage%}}, {{Parameter|destinationPage%}}


{{PageDescription}}
* {{Parameter|sourcePage%}} is an image page in video memory.
* {{Parameter|destinationPage%}} is the video memory location to copy the source image to.
* The working page is set as 0. All drawing occurs there.
* The visible page is set as any page number that the SCREEN mode allows.
* The [[_DISPLAY (function)]] return can be used a page number reference in '''QB64''' (See Example 1).
* The '''QB64''' [[_DISPLAY]] statement can also be used to stop screen flicker without page flipping or [[CLS]] and '''is the recommended practice'''.


==QBasic/QuickBASIC==
* {{Parameter|sourcePage%}} and {{Parameter|destinationPage%}} numbers are limited by the SCREEN mode used. In '''QB64''', the same limits don't apply.


{{PageExamples}}
''Example 1:'' Creating a mouse cursor using a page number that '''you create''' in memory without setting up page flipping.
{{CodeStart}}
{{Cl|SCREEN (statement)|SCREEN}} {{Cl|_NEWIMAGE}}(640, 480, 32) 'any graphics mode should work without setting up pages
{{Cl|_MOUSEHIDE}}
SetupCursor
{{Cl|PRINT}} "Hello World!"
{{Cl|DO}}: {{Cl|_LIMIT}} 30
  {{Cl|DO}} {{Cl|WHILE}} {{Cl|_MOUSEINPUT}}: {{Cl|LOOP}} 'main loop must contain _MOUSEINPUT   
'       other program code    
{{Cl|LOOP}}

{{Cl|SUB}} SetupCursor
{{Cl|ON TIMER(n)|ON TIMER}}(0.02) UpdateCursor
{{Cl|TIMER}} ON
{{Cl|END SUB}}

{{Cl|SUB}} UpdateCursor
{{Cl|PCOPY}} {{Cl|_DISPLAY (function)|_DISPLAY}}, 100  'any page number as desination with the _DISPLAY function as source
{{Cl|PSET}} ({{Cl|_MOUSEX}}, {{Cl|_MOUSEY}}), {{Cl|_RGB}}(0, 255, 0)
{{Cl|DRAW}} "ND10F10L3F5L4H5L3"
{{Cl|_DISPLAY}}                  'statement shows image
{{Cl|PCOPY}} 100, {{Cl|_DISPLAY (function)|_DISPLAY}} 'function return as destination page
{{Cl|END SUB}} '' ''
{{CodeEnd}}
:''Note:'' Works with [[_DISPLAY (function)]] as the other page. If mouse reads are not crucial, put the _MOUSEINPUT loop inside of the UpdateCursor Sub.


''Example 2:'' Bouncing balls
{{CodeStart}} '' ''
 {{Cl|SCREEN (statement)|SCREEN}} 7, 0, 1, 0
 {{Cl|DIM}} x(10), y(10), dx(10), dy(10)
 {{Cl|FOR...NEXT|FOR}} a = 1 {{Cl|TO}} 10
   x(a) = {{Cl|INT}}({{Cl|RND}} * 320) + 1
   y(a) = {{Cl|INT}}({{Cl|RND}} * 200) + 1
   dx(a) = ({{Cl|RND}} * 2) - 1
   dy(a) = ({{Cl|RND}} * 2) - 1
 {{Cl|NEXT}}
 {{Cl|DO...LOOP|DO}}
 {{Cl|PCOPY}} 1, 0                           'place image on the visible page 0
 {{Cl|CLS}}
 {{Cl|_LIMIT}} 100                           'regulates speed of balls in QB64
 {{Cl|FOR...NEXT|FOR}} a = 1 {{Cl|TO}} 10     
   {{Cl|CIRCLE}}(x(a), y(a)), 5, 15          'all erasing and drawing is done on page 1
    x(a) = x(a) + dx(a)
    y(a) = y(a) + dy(a)
   {{Cl|IF...THEN|IF}} x(a) > 320 {{Cl|THEN}} dx(a) = -dx(a): x(a) = x(a) - 1
   {{Cl|IF...THEN|IF}} x(a) < 0 {{Cl|THEN}} dx(a) = -dx(a): x(a) = x(a) + 1
   {{Cl|IF...THEN|IF}} y(a) > 200 {{Cl|THEN}} dy(a) = -dy(a): y(a) = y(a) - 1
   {{Cl|IF...THEN|IF}} y(a) < 0 {{Cl|THEN}} dy(a) = -dy(a): y(a) = y(a) + 1
 {{Cl|NEXT}}
 {{Cl|DO...LOOP|LOOP}} {{Cl|UNTIL}} {{Cl|INKEY$}} = {{Cl|CHR$}}(27) ' escape exit
{{CodeEnd}}
:''Explanation:'' PCOPY reduces the flickering produced by clearing the screen. x(a) = x(a) - 1, etc. is just to be safe that the balls stay within the boundaries. dx(a) = -dx(a), etc. is to keep the actual speed while inverting it (so that the ball "bounces"). The rest should be self-explanatory, but if you are unsure about arrays you might want to look at QB64 Tutorials -> [[Arrays]].


{{PageSeeAlso}}
* [[_DISPLAY]]
* [[SCREEN (statement)]]


{{PageNavigation}}
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