ScreenUnlock
 
Unlocks work page's framebuffer

Syntax

Declare Sub ScreenUnlock ( ByVal startline As Integer = -1, ByVal endline As Integer = -1 )

Usage

ScreenUnlock [ start_line ] [, end_line ]

Parameters

startline
optional argument specifying first screen line to be updated. If omitted, top screen line is assumed.
endline
optional argument specifying last screen line to be updated. If omitted, bottom screen line is assumed.

Description

ScreenUnlock unlocks the current work page assuming it was previously locked by calling ScreenLock and lets the system restart updating the screen regularly. When called with start_line and end_line , only the screen area between those lines is assumed to have changed, and will be updated.

An internal counter exists that remembers the screen lock state, thus ScreenUnlock has an effect only on a screen that is locked. A screen that has not been locked with ScreenLock cannot get unlocked, however ScreenUnlock still will force an update of given area or full screen.

Calls to ScreenUnlock must be paired with a matching call to ScreenLock. Only the first call to ScreenLock actually performs a locking operation. Subsequent calls to ScreenLock only increment the counter. Conversely, ScreenUnlock only decrements the lock counter until it reaches zero at which time the actual unlock operation will be performed. Using Screen or ScreenRes will release all locks and set the lock counter back to zero before changing screen modes.

After ScreenUnlock is called, all graphics statements still may be safely used, OTOH accessing the work page framebuffer directly via ScreenPtr may only be used after locking the screen again with ScreenLock.

Warning (Win32, Linux) : The screen is locked by stopping the thread that processes also the OS' events. This means the screen should be locked only for the short time required to redraw it, and no user input will be received while the screen is locked.

Example

See ScreenPtr example.

Dialect Differences

  • Not available in the -lang qb dialect unless referenced with the alias __Screenunlock.

Differences from QB

  • New to FreeBASIC

See also