Do I unnderstand this right?

Post #241,532 by drewk 1/16/06 5:03:27 PM Reply	Do I unnderstand this right? I heard it had to do with printing images, and the ability to abort a print job. Is that appropriate to put in the image code, and not the printing code? I guess for really large files on older hardware it could take a while to finish converting it into a printable format and you'd want to be able to interrupt it. But wouldn't it make more sense <question class="from ignorance">to spawn a thread for the printing, and if you receive the interrupt from the printing system you just kill that one thread?<question> === Purveyor of Doc Hope's [link\|http://DocHope.com\|fresh-baked dog biscuits and pet treats]. [link\|http://DocHope.com\|http://DocHope.com]
Post #241,538 by boxley 1/16/06 5:17:35 PM Reply	did $MS understand multithreading when they wrote it? Any opinions expressed by me are mine alone, posted from my home computer, on my own time as a free american and do not reflect the opinions of any person or company that I have had professional relations with in the past 50 years. meep
Post #241,548 by JayMehaffey 1/16/06 6:38:38 PM Reply	It is part of that I guess for really large files on older hardware it could take a while to finish converting it into a printable format and you'd want to be able to interrupt it. But wouldn't it make more sense <question class="from ignorance">to spawn a thread for the printing, and if you receive the interrupt from the printing system you just kill that one thread?<question> The function in question is the one a program uses to tell Windows that you want that interrupt and where you want that notification send in your program. But this function not for the conversion phase, it is for the actual printing part. This is to handle the case where the program is done with the printing entirly, but the physical pages are not done coming out of the printer. This lets the program get notification if the print job is stopped after the program is done with it. As for why the function exists at all for WMF and display routines, it is because of Windows unified drawing subsystem. Windows, in theory, has one set of drawing functions that are used for all output contexts. WMF are really just a way of storing those drawing commands in a file, and thus WMFs have access to the same functions as display and printer routines. Jay
Post #241,570 by broomberg 1/16/06 9:08:08 PM Reply	No. He was using the explanation of printing VS viewing as a reason why MS MIGHT have screwed up and done it by accident. If a file is going to the print subsystem, there is the possibility that the job will need to be aborted after the hand-off. So there is the ability to drop a callback into the file that will allow the print subsystem to check if it has been aborted. The callback is a 4 byte address in the submitting program's memory space, which hold a routine, and will tell the print subsystem whether the job should be aborted. This is a different. In this case, there is an illegal instruction in the wmf file that is VERY unlikely to be there by accident. It essential saya that the length of the data to follow is 1 byte, but since it is dealing in words is must be at LEAST 4 bytes. Combined that with the abort instruction. And then, rather than jump to a callback (which would be appropriate if this was a mistake, ie: cut-and-paste of the underlying code that make no sense for viewing rather than printing), start executing code contained within the image file. This also means there is no return to current operation, since the stack is destroyed,

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