PCopy
Copies one graphical or text page onto another
Syntax
`
Declare Function PCopy ( ByVal source As Long = -1, ByVal destination As Long = -1 ) As Long
`
Usage
`
PCopy [ source ] [, destination ]
`
Parameters
`source`
page to copy from
`destination`
page to copy to
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 omitted, the current visible page is assumed.
`PCopy` is inactive if the `destination` page is locked.
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 displayed page to 0
ScreenSet 1, 0
'Draws a circle moving across the top 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 for a keypress before the screen closes
Sleep
`
`
'' 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
#endif
Dim As Integer i, frames, fps
Dim As Double t
t = Timer
Do
'' Fill working page with a certain color and character
Cls
Locate 1, 1
Color (i And 15), 0
Print String$(80 * 25, Hex$(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 frame to free up cpu time
Sleep 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.
- Maximum number of graphics pages depends on what was specified when the `Screen` or `ScreenRes` statement was called.

Differences from QB

- None

See also

- `ScreenCopy`
- `Flip`
- `Screen`