I am the one Christian Heilmann was referring to in his post. I am happy to report that I could at least resolve/figure out one thing about Slack that was driving me crazy from the first time I tried it. And that is the scrolling behaviour in the iOS client. The iOS client, as mentioned in another response, accessible to VoiceOver users. VoiceOver, for those not familiar with it, is an accessibility function built into iOS that allows blind and visually impaired users to use these devices, too. It changes the gestures so touching something does not automatically activate that item, but speaks it. To activate, you double-tap somewhere on the screen.
VoiceOver has some more features that can help more easily navigate the user interface of an app. You swipe left and right with one finger to go from item to item, for example. In Twitter clients and Facebook, as well as built-in apps like Mail or Messages, you can use that to scroll even really long lists and read them in sequential, or reverse, order. Another feature is a 3 finger tap to tell you which page of content is being displayed (e. G. Rows 24 to 35 of 283). You can then swipe down with 3 fingers to show the next items at the top, or swipe up with 3 fingers to pull up the next items from 35 onwards. When you swipe with one finger, in most situations, the screen simply scrolls with you so you don’t have to bother with the 3 finger gestures.
However, in Slack, this whole concept behaves entirely differently. When you initially launch the app, you are presented with your last channel, and the newest messages showing. Tapping one of those messages will read it, and swiping left and right will move from message to message. In the current range, the most recent is at the bottom, above the text field for your own writing, and the oldest is at the top. However, if you continue to swipe to the left to reach the top, effectively reading messages in reverse order, you’ll reach a point where VoiceOver will jump to elements outside the main message area. This is odd, since there will most likely be older messages.
Tapping any of the current messages, then doing a 3 finger tap will say something like „rows 1 to 16 of 48". OK, this is the first odd thing. I am apparently on the first page of messages, but it is showing the last messages in the chat window. Subsequently, trying to swipe downwards will reveal no new content. But swiping upwards with 3 fingers will now scroll to rows 17 to 32 of 48. Touching the top-most message will reveal that it is from some time further back in history. Progressing towards the bottom will get me closer to the point where my previous page, rows 1 to 16, started at the top. So swiping down with 3 fingers revealed older content, starting at the top again, and if I want to read in non-reverse order, I first have to find where my new messages are, then read each page to the bottom, then swipe down with 3 fingers and start from the top of the screen again to read in sequential order.
This so goes completely against the conventions of virtually all other iOS clients I’ve seen so far. And I’ve been using iOS apps since VoiceOver’s inception in the iPhone 3G S in June 2009. It took me literally a four-o’clock-in-the-morning moment during a restless night to finally figure out how this thing is working! And I cannot even begin to imagine what visual indicators you sighted folks get to figure out how scrolling works in the Slack iOS client! :-)