SCREENSET


Sets current work and visible pages

Syntax:
declare sub Screenset ( byval work_page as long = -1, byval visible_page as long = -1 )

Usage:
Screenset [ work_page ] [, visible_page ]

Parameters:
work_page
index to working page
visible_page
index to visible page

Description:
Screenset allows to set the current working page and the current visible page. Page numbers range from 0 to num_pages - 1, where num_pages is the number of pages specified when setting the graphics mode with Screenres or Screen. You can use this function to achieve page-flipping or double-buffering.

If you provide visible_page but omit work_page, only the visible page is changed. If you provide work_page but omit visible_page, only the work page is changed. If you omit both arguments, both work page and visible page are reset to page 0.

Screenset provides one method of writing to the screen without instantly displaying changes to the user. See also Screenlock / Screenunlock for an alternative method of doing this.

Note: The current cursor position is not handled independently for each video page. Therefore, when another working page is selected, the starting cursor position corresponds to the last cursor position on the previous working page (same behavior for the text cursor and the graphics cursor).

Examples:
' Open graphics screen (320*200, 8bpp) with 2 pages
ScreenRes 320, 200, 8, 2

' Work on page 1 while displaying page 0
ScreenSet 1, 0

Dim As Integer x = -40

Do
    '' Clear the screen, draw a box, update x
    Cls
    Line (x, 80)-Step(39, 39), 4, BF
    x += 1: If (x > 319) Then x = -40
   
    ' Wait for vertical sync: only used to control refresh rate, can be put anywhere in the Do loop
    ScreenSync
   
    ' Copy work page to visible page
    ScreenCopy
   
Loop While Inkey = ""


Dialect Differences:
Differences from QB:
See also:
Back to Screen Functions
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