Make the star ratings in the tracks view editable via keyboard

[cr7pt0gr4ph7]

It is now possible to press enter the edit key (F2, or, once #13148 is merged, 'R` resp. the confiugured edit key) on a selected "star rating" to then change the rating via the keyboard (either left/right arrow keys or numbers). Changing the rating using the mouse is still possible, and should work & interact with the keyboard edits as expected.

But why is this PR so large?

The code for handling the actual keyboard edits is quite simple. Nearly all of the complexity relates to handling the interaction between editing via mouse hover, editing via keyboard and the assumptions of the Qt QTableView framework code.

In short: Cells in the QTableView can either be in "edit mode" or "display mode". Pressing the edit key should enter edit mode, canceling or committing the edit should leave edit mode. BUT: The cells should also automatically enter edit mode when the mouse hovers over the cell, and exit it when the mouse leaves the cell. The rating should also temporarily adapt to the position of the mouse when hovering over the cell. But what happens e.g. when the user presses the edit key while already hovering over the cell?

All in all, the desired (and hereby implemented) behavior boils down to the following state machine:

PlantUML Diagram

All commits have been extensively documented. If I may, I would recommend reviewing the commits in isolation.

[ronso0]

Just a note

It is now possible to press enter on a selected "star rating" to then change the rating via the keyboard

Enter/Return currently triggers the configured double-click action, so in order to use Enter one woud have to select 'ignore' in the preferences, right?
I assume you'll map this to the new Edit key introduced in #13148? (once that's merged)

[ronso0]

Another quick note:
currently, star ratings range from 0-5, so let's use onyl those keys, and add a note to

mixxx/src/track/trackrecord.h

Line 78 in 60bdaca

static constexpr int kMaxRating = 5;

[cr7pt0gr4ph7]

(Edit: Sorry, reply got way longer than intended. TLDR: It causes no issues and is not more complex to maintain than a TODO comment in an "unrelated" file. If you insist, I have no problem with removing those lines though).

---

I see your point, but I'd argue in favor of keeping it the way it currently is:

• User Interaction: We prevent all key press events from moving up the parent chain anyway while in edit mode (see line 201) to be consistent with the way the other editors work, so the user does not gain something from not handling the keys 6 to 9.
  

  mixxx/src/library/tabledelegates/stareditor.cpp

  Lines 192 to 194 in c59a384

  	// Prevent other keys from being handled as global keyboard shortcuts.
  	// This matches the behavior of the other edit controls.
  	return true;

  
  We clamp to the valid rating range anyway, so I even think supporting all numbers on the numpad makes this feature ever so slightly more discoverable.
• API Consistency: StarRating has a maxStarCount method, so I (as a developer) would in principle expect StarEditor it to work nicely with every StarRating object I pass it, including those with max ratings other than 5, if I were to reuse it in some other place.
  

  mixxx/src/library/starrating.h

  Lines 23 to 35 in 3c1d44c

  	explicit StarRating(
  	int starCount = kMinStarCount,
  	int maxStarCount = mixxx::TrackRecord::kMaxRating - mixxx::TrackRecord::kMinRating);
  	void paint(QPainter* painter, const QRect& rect) const;
  	QSize sizeHint() const;
  	int starCount() const {
  	return m_starCount;
  	}
  	int maxStarCount() const {
  	return m_maxStarCount;
  	}

• Code complexity: If not for user/developer experience: What is to be gained from replacing a few lines of simple, perfectly working code with a TODO comment in an "unrelated" file?

[ronso0]

Sure, your points are valid.

Mine was simply about YAGNI ; )

[cr7pt0gr4ph7]

No offense meant or taken ; )

YAGNI is valid, but as always it's a tradeoff : )

So, ready to merge if there are no other objections?

[cr7pt0gr4ph7]

Just a note

It is now possible to press enter on a selected "star rating" to then change the rating via the keyboard

Enter/Return currently triggers the configured double-click action, so in order to use Enter one woud have to select 'ignore' in the preferences, right? I assume you'll map this to the new Edit key introduced in #13148? (once that's merged)

Good catch, this was an error I made while writing the summary. Yes, it's mapped to the edit action (triggered by F2, or also custom keys in the future) like with any other editable cell. I've updated the PR description.