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84 lines
3.6 KiB
Plaintext
84 lines
3.6 KiB
Plaintext
The [[PCOPY]] statement copies one source screen page to a destination page in memory.
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{{PageSyntax}}
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: [[PCOPY]] {{Parameter|sourcePage%}}, {{Parameter|destinationPage%}}
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{{PageDescription}}
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* {{Parameter|sourcePage%}} is an image page in video memory.
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* {{Parameter|destinationPage%}} is the video memory location to copy the source image to.
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* The working page is set as 0. All drawing occurs there.
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* The visible page is set as any page number that the SCREEN mode allows.
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* The [[_DISPLAY (function)]] return can be used a page number reference in '''QB64''' (See Example 1).
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* The '''QB64''' [[_DISPLAY]] statement can also be used to stop screen flicker without page flipping or [[CLS]] and '''is the recommended practice'''.
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==QBasic/QuickBASIC==
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* {{Parameter|sourcePage%}} and {{Parameter|destinationPage%}} numbers are limited by the SCREEN mode used. In '''QB64''', the same limits don't apply.
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{{PageExamples}}
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''Example 1:'' Creating a mouse cursor using a page number that '''you create''' in memory without setting up page flipping.
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{{CodeStart}}
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{{Cl|SCREEN (statement)|SCREEN}} {{Cl|_NEWIMAGE}}(640, 480, 32) 'any graphics mode should work without setting up pages
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{{Cl|_MOUSEHIDE}}
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SetupCursor
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{{Cl|PRINT}} "Hello World!"
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{{Cl|DO}}: {{Cl|_LIMIT}} 30
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{{Cl|DO}} {{Cl|WHILE}} {{Cl|_MOUSEINPUT}}: {{Cl|LOOP}} 'main loop must contain _MOUSEINPUT
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' other program code
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{{Cl|LOOP}}
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{{Cl|SUB}} SetupCursor
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{{Cl|ON TIMER(n)|ON TIMER}}(0.02) UpdateCursor
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{{Cl|TIMER}} ON
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{{Cl|END SUB}}
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{{Cl|SUB}} UpdateCursor
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{{Cl|PCOPY}} {{Cl|_DISPLAY (function)|_DISPLAY}}, 100 'any page number as desination with the _DISPLAY function as source
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{{Cl|PSET}} ({{Cl|_MOUSEX}}, {{Cl|_MOUSEY}}), {{Cl|_RGB}}(0, 255, 0)
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{{Cl|DRAW}} "ND10F10L3F5L4H5L3"
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{{Cl|_DISPLAY}} 'statement shows image
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{{Cl|PCOPY}} 100, {{Cl|_DISPLAY (function)|_DISPLAY}} 'function return as destination page
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{{Cl|END SUB}} '' ''
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{{CodeEnd}}
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:''Note:'' Works with [[_DISPLAY (function)]] as the other page. If mouse reads are not crucial, put the _MOUSEINPUT loop inside of the UpdateCursor Sub.
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''Example 2:'' Bouncing balls
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{{CodeStart}} '' ''
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{{Cl|SCREEN (statement)|SCREEN}} 7, 0, 1, 0
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{{Cl|DIM}} x(10), y(10), dx(10), dy(10)
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{{Cl|FOR...NEXT|FOR}} a = 1 {{Cl|TO}} 10
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x(a) = {{Cl|INT}}({{Cl|RND}} * 320) + 1
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y(a) = {{Cl|INT}}({{Cl|RND}} * 200) + 1
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dx(a) = ({{Cl|RND}} * 2) - 1
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dy(a) = ({{Cl|RND}} * 2) - 1
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{{Cl|NEXT}}
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{{Cl|DO...LOOP|DO}}
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{{Cl|PCOPY}} 1, 0 'place image on the visible page 0
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{{Cl|CLS}}
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{{Cl|_LIMIT}} 100 'regulates speed of balls in QB64
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{{Cl|FOR...NEXT|FOR}} a = 1 {{Cl|TO}} 10
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{{Cl|CIRCLE}}(x(a), y(a)), 5, 15 'all erasing and drawing is done on page 1
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x(a) = x(a) + dx(a)
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y(a) = y(a) + dy(a)
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{{Cl|IF...THEN|IF}} x(a) > 320 {{Cl|THEN}} dx(a) = -dx(a): x(a) = x(a) - 1
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{{Cl|IF...THEN|IF}} x(a) < 0 {{Cl|THEN}} dx(a) = -dx(a): x(a) = x(a) + 1
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{{Cl|IF...THEN|IF}} y(a) > 200 {{Cl|THEN}} dy(a) = -dy(a): y(a) = y(a) - 1
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{{Cl|IF...THEN|IF}} y(a) < 0 {{Cl|THEN}} dy(a) = -dy(a): y(a) = y(a) + 1
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{{Cl|NEXT}}
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{{Cl|DO...LOOP|LOOP}} {{Cl|UNTIL}} {{Cl|INKEY$}} = {{Cl|CHR$}}(27) ' escape exit
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{{CodeEnd}}
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:''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]].
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{{PageSeeAlso}}
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* [[_DISPLAY]]
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* [[SCREEN (statement)]]
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{{PageNavigation}}
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