Some issues with large files

[zonkmachine]

In response to two related crashes in SampleBuffer.cpp as commented in #3205
I substituted the command line messages for a message box.
I haven't touched the original 100 MB size limit and have added a 1 hour length check.

---

FIx explained:
I add a bool, fileLoadError, which is set to false, should the file fail on one of the tests. I add a test for file length as a compressed file of small size when decompressed will take a much bigger size so the important fact to know for LMMS is not the file size but the length of the sample. This operation takes a bit of time to carry out compared to the file size test so we wait to see if that one passes and then carry on testing the length of the sample.
If the file is marked fileLoadError == true, the buffer will be written with one sample, value 0, and after removing possible locks a message is shown. The message is only for information and is shown after the locks are removed so the project isn't frozen while waiting for 'OK' to be pressed. The old message was to the command line and of little use to an ordinary user.

Some issues that remain with opening large files:

• Previewing large files is sluggish. The file tests works however but large file within the limit are still loaded in their entirety. If you open large files you do it from the track container rather than the menu.
• After failing to load a file on being to large the buffer is zeored and you might want to keep the old file in case of a fail. In order to fix this you (probably) need to test the file earlier, before calling SampleBuffer::update() .

[zonkmachine]

This is ready for review.

[zonkmachine]

I moved the message box to the end as it would interrupt the song playing. First take care of everything and remove lock, then disappoint the user...

Me thinks SampleBuffer::update( ... ) is trying to do a bit too much. The file checks could be done in a separate function, and in advance of updating it, and then we can avoid writing blank, 1 sample buffers, on loading a new sample that fails. I think it's more useful to keep the old one in case this happens.

[zonkmachine]

I've updated the first post with an explanation of the fix. I think this is a reasonable fix for now.

[tresf]

I've updated the first post with an explanation of the fix. I think this is a reasonable fix for now.

You've added a QMessageBox to a non-gui class, so I still think we need to check for a GUI via if(gui) ... despite the near-impossible likelihood of a command-line render with a 60 minute sample.

[zonkmachine]

OK, fixed that. Stumbled upon #3338 so I had to backport to 6137fcc to test this.

$ ./lmms -r ~/lmms/projects/buggar/largeSamples/90min.mmp -o test.wav
...
Loading project...
Audio files are limited to 100 MB in size and 1 hour of playing time
$