When a desktop theme manager isn't available, LC reverts to its built-in
emulated Motif, hence the odd appearance (which is awesome if you love
NeXT, and horribly confusing to literally every newcomer if they're not
ancient enough to remember the old Unix UI and know the intricacies of
MetaCard's history, or even what MetaCard was).
For mobile, LC suggests hand-scripting a overlay object to handle the
user interation and graphical feedback for scrollable controls like
fields and groups.
In practice, most devs I know don't type those manually, but have
written their own routines that automatically instantiate mobile
scrollers by examining controls on preOpenCard and setting up the
scrollers as needed.
I do not know why this is impossible for the engine to do, but it's easy
enough to work around in a script.
--
Richard Gaskin
Fourth World Systems
Mobile Wondering <was Maximum field height?>
Neville Smythe neville.smythe at optusnet.com.au
Mon Apr 6 13:50:27 EDT 2020
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I had been wondering when the third-class status of mobile platforms in the LC
world, particularly in relation to scrolling fields and groups, would crop up
here.
Some time ago I looked at converting an iOS project to LC, and was appalled at
the crude 1984-style appearance of scroll bars. I presume they look that way to
inhibit their use, since the scrolling idiom on mobile platforms iOS is quite
different from the desktop. But I reckon the native-scroller thingy which you
had to use in its place seemed an awful hack: its appearance in a different
layer meant other objects got overwritten in a completely unacceptable way (has
that changed?); and the separation of the testing regime from the IDE turned
back the clock on the development process, again to 1984 when you developed on
the Lisa, tested on the Mac. (Yes, I was there!)
So I developed a custom scrollbar which worked on both desktop and iOS. It is
doable, with a modicum of fiddly stuff.
You need
1. An installer stack or widget. When you drag a scrollbar template onto a field (or group), it registers the field id with the scrollbar, snaps the scrollbar to fit the field dimensions with the desired vertical or horizontal orientation, and adjusts the thumb to match the field content. It also installs a backscript and frontscript in the stack.
2. The front script captures mouse events/ drag touch gestures intended for the field, filters for scrolling events and diverts those to the appropriate custom scrollbar. For 2-dimensional scrolling I used two separate scrollbars which needed some cross-mediation of gesture directions; a combined double-scrollbar would have been better.
3. The backscript catches changes to the field affecting content, position or
dimensions which need to be reflected in the scrollbars.
I had it working pretty well, to the point of a mostly complete examples /
installer stack . You can customise all sorts of things, such as the appearance
of the thumb and scrollbar background, whether the thumb length should reflect
field content proportionally or not, visible-on-demand or as-needed or hidden
thumb, the number of thumb positions - for example you could have a stepper
with just 5 positions and a custom image as thumb - and even have left side or
top mounted scrollbars. You could even have a desktop look and feel if you
wanted, and why not if Apple can flout their own UI guidelines?
The iOS project lapsed, running the maze of Apple distribution requirements
became discouraging and I lost interest. But it can be done.
Neville
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