Pattern and instrument drag & drop preview

[cme]

Preview drag and drop operations in the SongEditorPatternList and PatternEditorInstrumentList, rearranging the patterns (or instruments) in the list to the order which will be imposed if the drag is ended at that position.

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[cme]

Tempted to refactor DropTargetKind and associated parameters to a new class...

[theGreatWhiteShark]

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Nowadays all drumkits accessible in the Sound Library widget are loaded (without samples) and stored in the SoundLibraryDatabase. The absolute path to the kits folder serves as the key to access them. SoundLibraryPanel::m_drumkitRegister maps the labels shown in the Sound Library widgets to the keys of the SoundLibraryDatabase. E.g. https://github.com/hydrogen-music/hydrogen/blob/master/src/gui/src/SoundLibrary/SoundLibraryPanel.cpp#L478

[theGreatWhiteShark]

I like it. But I have some remarks.

• it feels a little strange that the associated row along with its notes/patterns is not moving as well
• the dragged item in the instrument list keeps the "selected" color but its counterpart in the pattern list does not
• maybe inserting and moving could have two different cursor icons. I haven't looked into to the drag and drop support of Qt5 yet but there are Qt::DragMoveCursor and Qt::DragCopyCursor in the docs. But for some reasons those icons aren't displayed.

[theGreatWhiteShark]

it feels a little strange that the associated row along with its notes/patterns is not moving as well

That's probably a more complex thing to implement.

I just thought about it a little more. I like your solution and I definitely don't want to step in and tell what it should look like. Just a thought :). In other applications drag move and drag additions are rendered by highlighting the border between two columns. This would probably be way less work then moving notes around. Also, we should think in advance about how to display a drag replacement of an instrument with another one (it's on the TODO list). Maybe something like highlighting its borders similar to what is happening when right-clicking a instrument/pattern element.

[cme]

I've sort of sat on this one for a while because, while I liked the initial idea, when it came to actually using it for some aggressive instrument reshuffling, I didn't like the way it felt. It seemed too disorienting, and reflecting about it I think this was because it shows only the "after" result of the action, and the fact that instruments and patterns move only in fixed amounts doesn't actually convey much "movement" when the cursor moves to a different block.

Maybe this could be fixed by highlighting the inserted/moved pattern or instrument as well, but on reflection I think showing a highlight at the drop site is actually better.