BBC BASIC for Windows - Commented Libraries

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Commented Libraries

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Topic: Commented Libraries (Read 936 times)

Malcolm
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Re: Commented Libraries
« Reply #2 on: Mar 23^rd, 2011, 4:41pm »

Anyone like to expand as to what this does and why?

[OPT 2
.K% push H% : call "SetFocus" : ret 16
.M% cmp dword [esp+8],&500 : jz K%
pop eax : push [^O%] : push eax : jmp "CallWindowProc"
]

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admin
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Posts: 1145

Re: Commented Libraries
« Reply #3 on: Mar 23^rd, 2011, 6:58pm »

on Mar 23^rd, 2011, 4:41pm, Guest-Malcolm wrote:

Anyone like to expand as to what this does and why?

It calls the SetFocus API, but in the context of the thread containing the message pump rather than the interpreter's thread.

The documentation of SetFocus says: "The SetFocus function sets the keyboard focus to the specified window. The window must be attached to the calling thread's message queue":

http://msdn.microsoft.com/en-us/library/ms646312.aspx

Since the interpreter's thread doesn't have a message queue, simply doing SYS "SetFocus" doesn't work.

Richard.

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Malcolm
Guest

Re: Commented Libraries
« Reply #4 on: Mar 23^rd, 2011, 11:02pm »

Thanks Richard,

I understand the concept of threads but not the practicality. I had better read up some more.

Malcolm.

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