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https://github.com/QB64-Phoenix-Edition/QB64pe.git
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6e01fc8dce
Added new _STRCMP and _STRICMP commands for quick string comparisons. Cleaned up QB64 to finish removing the QUI (quick user insert) code and folders. Altered UCASE and LCASE routines to be faster in some situations for us.
40 lines
2.1 KiB
Plaintext
40 lines
2.1 KiB
Plaintext
The {{KW|_DISPLAY}} statement turns off automatic display while only displaying the screen changes when called.
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{{PageSyntax}}
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::: '''_DISPLAY''
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''Usage:''
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* '''_DISPLAY''' turns off the default [[_AUTODISPLAY]] when used. Prevents screen flickering.
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* Call _DISPLAY each time the screen graphics are to be displayed. Place call after the image has been changed.
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* Re-enable the automatic display by calling [[_AUTODISPLAY]]. If it isn't re-enabled, things may not be displayed later!
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''Examples:'' Displaying a circle bouncing around the screen.
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{{CodeStart}} '' ''
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{{Cl|SCREEN (statement)|SCREEN}} 12
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x = 21: y =31 'start position
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dx = 3: dy = 3 'number of pixel moves per loop
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{{Cl|DO}}
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{{Cl|_LIMIT}} 100 ' set to 100 frames per second
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x = x + dx: y = y + dy
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{{Cl|IF...THEN|IF}} x < 0 {{Cl|OR}} x > 640 {{Cl|THEN}} dx = -dx 'limit columns and reverse column direction each side
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{{Cl|IF...THEN|IF}} y < 0 {{Cl|OR}} y > 480 {{Cl|THEN}} dy = -dy 'limit rows and reverse row direction top or bottom
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IF px <> x OR py <> y THEN FOR d = 1 to 20: CIRCLE (px, py), d, 0: NEXT 'erase
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FOR c = 1 TO 20: {{Cl|CIRCLE}} (x, y), c, 6: NEXT 'draw new circle at new position
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px = x: py = y 'save older coordinates to erase older circle next loop
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{{Cl|_DISPLAY}} 'after new circle is set, show it
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{{Cl|LOOP}} {{Cl|UNTIL}} {{Cl|INKEY$}} = CHR$(27) '' ''
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{{CodeEnd}}
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:''Explanation:'' The loop is set with [[_LIMIT]] to 100 frames per second to limit CPU usage and the speed of the ball. Each loop a circle is drawn while the previous one is erased when the coordinates change. _DISPLAY only shows the new circle position once each loop. The '''_DISPLAY''' routine eliminates the need for setting [[SCREEN (statement)|SCREEN]] swap pages, [[CLS]] and [[PCOPY]]. _DISPLAY keeps the image off of the screen until the changes have all completed. Drawing 40 circles every loop helps slow down the ball.
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{{PageSeeAlso}}
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* [[_AUTODISPLAY]] {{text|(default mode)}}
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* [[PCOPY]]
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* [[_DISPLAY (function)]]
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{{PageNavigation}} |