Pre Filter Code

Entry
R0	Event mask
R1	~~Users event buffer~~
R2	Task handle of task that called Wimp_Poll
R3	Pointer to poll word if applicable
R12	Value of R2 when filter registered

Exit
It must preserve all registers (other than R0)

You may clear bits in R0 to provide a new event mask.

Please note: You must preserve all other registers (other than R0).

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RISC OS is an Open Source operating system owned by RISC OS Developments Ltd and licensed primarily under the Apache 2.0 license.