PCopyfunction

Copies one graphical or text page onto another

Syntax

Declare Function PCopy ( ByVal source As Long = -1, ByVal destination As Long = -1 ) As Long

Parameters

Name		Description
`source`		page to copy from
`destination`		page to copy to

Return value

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 omitted, the current visible page is assumed.

PCopy is inactive if the destination page is locked.

The error code returned by PCopy can be checked using Err in the next line. The function version of PCopy returns directly the error code as a 32 bit Long.

Remarks

Usage



PCopy [ source ] [, destination ]

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 (Graphics) or ScreenRes statement was called.

Differences from QB

None

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

'' 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

#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$)

Reference

Documented in KeyPgPcopy.html