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84 lines
3.7 KiB
Plaintext
84 lines
3.7 KiB
Plaintext
{{DISPLAYTITLE:_DISPLAY}}
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The [[_DISPLAY]] statement turns off the automatic display while only displaying the screen changes when called.
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{{PageSyntax}}
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: [[_DISPLAY]]
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{{PageDescription}}
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* '''_DISPLAY''' turns off the auto refresh screen default [[_AUTODISPLAY]] behavior. 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 automatic display refreshing by calling [[_AUTODISPLAY]]. If it isn't re-enabled, things may not be displayed later.
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* _DISPLAY tells '''QB64''' to render all of the hardware [[_PUTIMAGE]] commands loaded into the buffer previously.
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* The [[_AUTODISPLAY (function)]] can be used to detect the current display behavior.
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* '''QB64''' can set the graphic rendering order of _SOFTWARE, _HARDWARE, and _GLRENDER with [[_DISPLAYORDER]].
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{{PageExamples}}
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''Example 1:'' 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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''Example 2:'' [[_DISPLAY]] must be used to render hardware images placed with [[_PUTIMAGE]] ('''version 1.000 and up''').
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{{CodeStart}} '' ''
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{{Cl|CONST}} MenuHeight = 200
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{{Cl|SCREEN}} {{Cl|_NEWIMAGE}}(640, 480, 32)
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'{{Cl|SLEEP}} 1
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{{Cl|LOCATE}} 20
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DO
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{{Cl|_LIMIT}} 30
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DisplayMenu
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k = {{Cl|_KEYHIT}}
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{{Cl|IF...THEN|IF}} k <> 0 {{Cl|THEN}} {{Cl|PRINT}} k,
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{{Cl|LOOP}} {{Cl|UNTIL}} k = 32 {{Cl|OR (boolean)|OR}} k = 27
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{{Cl|SUB}} DisplayMenu
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{{Cl|STATIC}} init, MS_HW {{Cl|AS}} {{Cl|LONG}}
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{{Cl|IF...THEN|IF}} {{Cl|NOT}} init {{Cl|THEN}}
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init = -1
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MS = {{Cl|_NEWIMAGE}}(640, MenuHeight, 32) 'MenuScreen image
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D = {{Cl|_DEST}}: {{Cl|_DEST}} MS
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{{Cl|CLS}} , {{Cl|&H}}FFAAAAAA 'background color gray
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{{Cl|_PRINTSTRING}} (20, 2), "Menu Test" 'image text
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MS_HW = {{Cl|_COPYIMAGE}}(MS, 33) 'create the MenuScreen_HardWare image
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{{Cl|_FREEIMAGE}} MS
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{{Cl|_DEST}} D
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{{Cl|END IF}}
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{{Cl|_PUTIMAGE}} (0, 0)-(640, MenuHeight), MS_HW
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{{Cl|_DISPLAY}}
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{{Cl|END SUB}} '' ''
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{{CodeEnd}}{{small|Code adapted by Galleon}}
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: ''Notes:'' When _DISPLAY is commented out, the hardware Menu Test screen portion will blink and key codes may be seen underneath.
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{{PageSeeAlso}}
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* [[_DISPLAY (function)]]
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* [[_DISPLAYORDER]]
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* [[_AUTODISPLAY]], [[_AUTODISPLAY (function)]]
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* [[_PUTIMAGE]]
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* [[PCOPY]]
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{{PageNavigation}}
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