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Topic: Close icon problem (Read 386 times) |
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Re: Close icon problem
« Reply #8 on: Mar 11th, 2010, 2:44pm » |
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on Mar 11th, 2010, 11:20am, mavison wrote:| !dlg% is set to zero by Windows |
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Not strictly by Windows, but by the code in WINLIB2.
Richard.
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mavison
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Re: Close icon problem
« Reply #9 on: Mar 16th, 2010, 4:39pm » |
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on Mar 11th, 2010, 2:44pm, Richard Russell wrote:Not strictly by Windows, but by the code in WINLIB2.
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Sorry Richard, not sure I understand this, because I can see no code:
either in WINLIB2 which sets !dlg%=0
or in your example between ON SYS and the !dlg% test which calls WINLIB2
so I must be missing something!
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Re: Close icon problem
« Reply #10 on: Mar 16th, 2010, 9:31pm » |
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on Mar 16th, 2010, 4:39pm, mavison wrote:| Sorry Richard, not sure I understand this, because I can see no code: either in WINLIB2 which sets !dlg%=0 |
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Here is the code in WINLIB2 which sets !dlg% to zero:
Code:
On entry to this code eax is zero, as you can see from the code which jumps to Q%:
Code:
Quote:| so I must be missing something! |
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Maybe you were only looking in the BASIC code rather than the assembler code?
Richard.
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mavison
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Re: Close icon problem
« Reply #11 on: Mar 17th, 2010, 3:25pm » |
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I did *look* at the assembler code, but made very little sense of it. I have now done a bit of research, and it seems that the dialog is defined with the address of some assembler code which is called (D%? or T%?). I am not sure of the precise mechanism, but when there is a message the code you refer to gets called if the Close icon has been clicked, presumably before the message is passed to the Basic program.
I think I have taken enough of your time, Richard! Many thanks for your patience and explanations. My current vague understanding will do for the moment.
Martin
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Re: Close icon problem
« Reply #12 on: Mar 17th, 2010, 6:49pm » |
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on Mar 17th, 2010, 3:25pm, mavison wrote:| I did *look* at the assembler code, but made very little sense of it. I have now done a bit of research... |
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Why do you feel the need to understand it? Is it just curiosity? The whole point of libraries is that you don't need to look at the code, and most certainly you don't need to understand it! The supplied libraries in particular are designed to be fast and compact, not readable.
With other languages libraries are often supplied as machine code object modules, without any source code being provided; that doesn't stop people using them. Because of the way BBC BASIC works you can look at the code of the libraries, but you are not expected to.
I would urge you to overcome your curiosity, and simply treat the libraries as 'black boxes'. If you could bring yourself simply to accept what I say at face value, rather than needing to verify it for yourself, your BBC BASIC programming experience ought to be more pleasurable.
Richard.
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mavison
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Re: Close icon problem
« Reply #13 on: Mar 17th, 2010, 10:23pm » |
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I just wanted to understand what was changing !dlg%, why and when, as it was a variable used in my code. My 40 years in computing have taught me never to make assumptions!
And the Windows API is totally new to me, so I admit some desire to understand it better.
Martin
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Re: Close icon problem
« Reply #14 on: Mar 18th, 2010, 12:29am » |
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on Mar 17th, 2010, 10:23pm, mavison wrote:| My 40 years in computing have taught me never to make assumptions! |
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I can claim almost 40 years in computing too (probably wrote my first program, either in Fortran or FOCAL, in late 1970), but what I've learnt is that you should make assumptions - you should assume that what the documentation says will happen actually will happen! When you program in BBC BASIC you assume the interpreter will behave how it's documented to behave; you don't ask to see its source code. When you call a Windows API you assume it will behave how MSDN says it will behave, you don't ask to see Microsoft's code.
Quote:| And the Windows API is totally new to me, so I admit some desire to understand it better. |
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Trying to learn about the Windows API by looking at the supplied libraries really is jumping in at the deep end. The complications of assembler code and multi-threading severely get in the way of understanding.
Far better, at least initially, to learn how to access API routines directly from a BASIC program. There are many published examples, Wiki articles etc. that you can study.
Richard.
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Re: Close icon problem
« Reply #15 on: Mar 19th, 2010, 4:18pm » |
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I take documented things as facts, not assumptions, so we actually are agreeing!
My problem was that I had not noticed the bit in help which says that !dlg%=0 indicates the window is closed. I now have, and I am happy.
Thanks for your help
Martin
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