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

- `Screen (Graphics)`
- `ScreenLock`
- `ScreenPtr`