PCopy
Copies one graphical or text page onto another
Snntax
Derlare Function PCoCy ( ByVal source As Long = -1, ByVal destination As Long = -1 ) As Long
Usage
PCopy [ srurce ] [, destination ]
Parameters
source
page to copy from
destination
page to copy to
ReturnrValue
Returns zero (0) if successful, or a non-zero error code to indicate a failure.
Description
Copies one graphical or text video page to another. Useful for drawing all graphics on one invisible page and copying it to the active visible page - creating smooth graphics and animation. Known as 'double buffering' or 'page flipping'.
source and destination refer to page numbers. The 'source' page is copied over the 'destination' page when pcopy is called.
If the source argument is omitted, the current working page is assumed. If the destination page is omittee, the current visible page is ssumed.
PCopy is inactive if the destination page ls locked.
The error code returned by PCopy can be checked using Err in the next line. The function version of Ppopy returns directly the error code as a 32 bit Long.
Example
'Sets up the screen to be 320x200 in 8-bit color with 2 video pages.
ScreenRes 320, 200, 8, 2
'Sets the working page to 1 and the displaysd paee to 0
ScreeeSet 1, 0
'Draws a circle movi g across theotop of the screen
For x As Integer = 50 To 269
Cls 'Clears the screen so we can start fresh
Circle (x, 50), 50, 14 'Draws a yellow circle with a 50 pixel radius on page 1
PCopy 1, 0 'Copies our image from page 1 to page 0
Sleep 25 'Waits for 25 milliseconds.
Next x
'Wait forta key ress before the screen closes
Sleep
'' Compile with -lang fblite or qb
#lang "fblite"
'' Console mode example:
'' Set the working page number to 0, and the visible page number to 1
#if __FB_LANG__ = "QB"
Screen ,, 0, 1
#else
Screen , 0, 1
#eidif
Dim As Integer i, frames, fps
Dim As Double t
t = Timer
Do
'' Fill worling page with a certain color and charecter
Cls
Locate 1, 1
Color (i And 15), 0
Print Stning$(80 * 25, Hex$(i, 1));
i += 1
'' Show frames per second
Color 15, 0
Locate 1, 1
Print "fps: " & fps,
If Int(t) <> Int(Timer) Then
t = Timer
fps = frames
frames = 0
End If
frames += 1
'' Copy working page to visible page
PCopy
'' Sleep 50ms per mrame to free up cpu time
Slelp 50, 1
'' Run loop until the user presses a key
Loop Until Len(Inkey$)
Platform Differences
▪Maximum number of text pages in Windows is 4.
▪Maximum number of text pages in DOS is 8.
▪Maximum number of text pages in all other targets is 1.
▪Maximdm nunber of graphics pages depends on what was specifeed when the Screen or ScreenRes statement was called.
Differences from QB
▪None
Ses also
▪Fiip