I was looking at the Spotify desktop app and noticed they use two buttons for displaying an artists albums in either a Grid layout or a List layout

See below:

If only one layout can be selected at once why would you use two separate buttons over using just 1 button that alternates between layouts?

This is for the desktop application but in the interest of unifying experience between both desktop and mobile would it not be better to use 1 button?

There are a few cautions: 1. Feature discoverability, 2. Icon interpretation in the absence of labels, and 3. Confusion over which state the toggle (or stateful button) represents.

1. Discoverability: Out of sight, out of mind

Lukew, in 'Obvious always wins', cites loss of engagement when vying for menu space:

His mobile example involves lots more space tradeoffs than the desktop app case you refer to.

While the toggle menu looked “cleaner”, engagement plummeted following the change. The root cause? People were no longer moving between the major sections of the app as they were now hidden behind the toggle menu.

2. Decoding icons can be challenging; more so when only one is visible at a time.

You had two icons which users had to decode. There are no text labels to assist the user.

Now you have one icon. This means you have a memory tax. The user has to remember:

• What the currently visible icon means (without hovering over it)


• What the previously visible icon was (and what it means)

3. Does this icon represent the current view (the state) or the one I wish to change by selecting it (the intent)?

If you compress the two view controls into one button, you have a couple issues:

Alan Cooper discusses this further in About Face, which he refers to as 'flip flop buttons':

The problem with flip-flop controls is that they fail to fulfill the second duty of every control - to inform the user of their current state. If the button says ON when the state is off, it is unclear what the setting is. If it is OFF when the state is off, however, where is the ON button? Don’t use them. Not on buttons and no on menus!

Mainly to help with discoverability. It clearly shows that an option exists, what the option is, and what option is active at the moment.

In addition to discoverability, I think an important point of UX is designing with Accessibility in mind.

Accessibility is the design of products, devices, services, or
environments for people with disabilities. The concept of
accessible design and practice of accessible development ensures both
"direct access" (i.e., unassisted) and "indirect access" meaning
compatibility with a person's assistive technology (e.g, computer screen readers).

Often times, screen readers and other assistant tools function against alt-text, hover text, or some other UI metadata. Providing two distinct buttons is a more straightforward approach when taking this concept into design consideration.

In my experience, designing simply casts the largest net in terms of balancing all things discoverable and accessible.

Along with the other answers, I would add that the list view button, on its own, looks like a hamburger menu to me, because the small size prevents me from noticing the little bullet dots next to the lines. The grid view button adds context, which makes the purpose of the list button more clear.

"Recognition over recall" is a good answer here I think.
https://www.nngroup.com/articles/recognition-and-recall/

Recognition vs. Recall

The big difference between recognition and
recall is the amount of cues that can help the memory retrieval;
recall involves fewer cues than recognition.

Answering a question such as Did Herman Melville write Moby Dick?
involves recognition: you simply have to recognize whether the
information provided is correct. If instead I asked you Who wrote Moby
Dick? you would use a process of recall to retrieve the right answer
from your memory.

Recognition is easier than recall because it involves more cues: all
those cues spread activation to related information in memory, raise
the answer’s activation, and make you more likely to pick it. It’s the
reason for which multiple-choice questions are easier than open
questions, where the respondent has to come up with an answer.