Is iOS scrolling modal?

Ilya Birman — Sat, 23 Sep 2017 12:33:39 +0500

Someone has tweeted this and got several retweets:

https://twitter.com/jordwalke/status/884553142813081601

What they mean is this: when the content is still, tapping the screen is interpreted as a tap, but when the content is in motion, tapping the screen just stops the motion. So is the behaviour modal? No, here’s why.

Most people think that an interface is modal when it has modes, i.e. when same user input produces different output depending on the state of the interface. However, that’s not the definition.

Let’s read Jef Raskin carefully:

An human-machine interface is modal with respect to a given gesture when (1) the current state of the interface is not the user’s locus of attention and (2) the interface will execute one among several different responses to the gesture, depending on the system’s current state.

Most people’s understanding includes only the (2), but not the (1). But they both equally matter. Perhaps, Raskin didn’t name the thing well, but we have what we have.

You unlock your iPhone and tap Messages:

But just as you are tapping it, you notice that it’s actually Shazam:

Oops, you are on a wrong page of your home screen.

In this case, launching of Shazam instead of Messages is a mode error: your gesture (tap in the top left corner) produced the wrong output depending on the current state (the page number), which was not your locus of attention. So, the iPhone’s home screen is modal.

Now let’s say you are in Contacts and tap the bottom left corner for Favourites:

Is there any chance you actually meant to go to a previously visited web page?

The gesture is the same (tap in the bottom left corner), and it produces different outputs depending on the current state (the active app). But here, the app is your locus of attention: you are fully aware whether you are looking for a contact or browsing the web. That’s why a modal error is not possible here, and this interface is not modal.

If we get back to iOS scrolling, it now becomes clear that it is not modal. When the scrolling animation is playing, it is the user’s locus of attention. The user is fully aware of the interface’s state: they are looking at the moving content. So the fact that the tap is interpreted differently during this animation is not a surprise and doesn’t produce a mode error.

Timed modes

Ilya Birman — Thu, 09 May 2013 03:02:25 +0500

Ilya Birman:

As you may know, modes are bad. Even worse are timed modes often used in the human interface of consumer electronics.

A mode is a state of user interface in which the same user action leads to the same result; in different modes, results of the same actions are different. Photoshop is famous for its exuberant use of modes: a click within an open image may do anything depending on what tool and options you have selected. The problem with modes is that you are not constantly aware of the current mode, which leads to errors: you want to draw a line, but accidentally create a gradient fill.

Now imagine a TV remote. Left-right buttons change volume and up-down buttons switch channels. These four buttons are also used for menu navigation. Now, when you are in the menu and you want to make the TV louder, you press the right button through habit. Unfortunatelly, now the button means “make screen aspect ratio wider”. The menu is not just a mode, it is a timed mode: if you don’t press anything for 10 seconds, the menu will be closed. If you are trying to set up this TV with a help of a user manual, you will be very frustrated: every time you look up the manual, the menu disappears and you have to start over.

Timed modes in a car UI are not just frustrating, but can also be dangerous. To change the audio bass level, you have to go to the menu, find the EQ settings, select “bass” and then adjust it with a knob. By the time you get to the necessary menu item, the traffic light turns green, so you have to postpone the adjustments until the next traffic light. Chances are, you will then need to navigate the menu again. If you know that the interface will not wait for you until the next traffic light, you will be forced to adjust bass while driving.

If you cannot avoid modes in your user interface altogether, at least don’t use timed modes. If I have changed my mind and don’t want to set up the TV or adjust the bass, I will just press cancel myself.

Блоги: заметки с тегом modes

Is iOS scrolling modal?

Timed modes