Screenunlock

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ScreenUnlock

Resumes screen updates after ScreenLock and shows what was drawn.

Syntax

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

Parameters

• startline
• endline

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

All graphic statements automatically lock the screen before the function call, and unlock the screen afterwards, so you do not need to do this explicitly using ScreenLock and ScreenUnlock. You only need to lock the screen when you wish to access the screen (framebuffer) directly using ScreenPtr or when you wish to group several graphic statements together so their effects appear simultaneously on screen, thus avoiding potential screen flicker during screen updates.

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. When the induced lock time becomes too long, use preferably the method of double buffering (with ScreenCopy).

Remarks

Usage

ScreenUnlock [ start_line ] [, end_line ]

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

Examples

See ScreenPtr example.

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Category: Screen Functions
Kind: sub

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Reproduced from the FreeBASIC Wiki Manual under the GNU Free Documentation License 1.3 — with no Invariant Sections, no Front-Cover Texts and no Back-Cover Texts. Copyright © the FreeBASIC project and wiki contributors. See License.