###### (This is the legacy documentation for stable SDL2, the current stable version; [SDL3](https://wiki.libsdl.org/SDL3/) is the current development version.)
# SDL_MUSTLOCK

Evaluates to true if the surface needs to be locked before access.

## Header File

Defined in [SDL_surface.h](https://github.com/libsdl-org/SDL/blob/SDL2/include/SDL_surface.h)

## Syntax

```c
#define SDL_MUSTLOCK(S) (((S)->flags & SDL_RLEACCEL) != 0)
```

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[CategoryAPI](CategoryAPI), [CategoryAPIMacro](CategoryAPIMacro), [CategorySurface](CategorySurface)