The regression affected AGOS and maybe some others; specifically,
the real MidiDriver would have been deleted twice -- I previously
missed that the Engine instances takes care of freeing the real
MidiDriver, not the MidiPlayer wrapping it.
This commit should clarify the ownership of the real MidiDriver for
most pseudo MidiDrivers.
Many engines follow the advice in audio/midiparser.h and create a
"pseudo-MidiDriver" subclass. But MidiParser really only needs a tiny
subset of the MidiDriver capabilities, namely those found in
MidiDriver_BASE. So we try to subclass from that whenever possible; this
allows us to remove many stub methods, and enables further future
simplifications.
The actual MidiDriver derives from it. MidiDriver_BASE only
provides the minimal API necessary for transmitting MIDI data.
The idea is that this is all MidiParser needs, thus allowing
us to simplify the various MidiPlayer classes in our engines.
I moved this TODO to the Wiki TODO page and extended it there. Yet
while I originally wrote it, I now think that we are probably best off
keeping things as they are.
This in turn enables modifying MidiDriver_MPU401::close() to allow
it to be called on a midi driver that has not yet been opened.
The specific issue that triggered me to make these changes was a
crash-upon-quit in HUGO, caused by it instantiating a midi driver,
then encountering an error (missing hugo.dat) *before* having
opened the new midi driver; the general cleanup code then tries
to close the (not yet opened) midi driver -> kaboom
Also fixed some engines which were leaking MidiDriver instances.
In the scumm help dialog, translate single keys, e.g. "Ctrl" or "Alt"
instead of asking the translator to translate individually "Ctrl a",
"Ctrl b", "Alt a", "Alt b", Ctrl Alt a" and so on. This reduce greatly the
number of strings to translate.
