[Tile-dev] Progress bars -- braindump

[Joe E. <jen...@fl...>]

Long-winded, half-thought-out rationale for why 
the ttk::progressbar currently works the way it does:

As mentioned before, from the program's POV there
seem to be three main modes of operation: "determinate",
"indeterminate", and "autoincrement".  The difference between
the latter two is that "indeterminate" mode can show
how fast something is going, where with "autoincrement"
mode you just want to make something move on the screen at
a steady rate until the operation completes.

On the user feedback side, there are many different variations;
"thermometer" mode, "barberpole" mode, and "cylon" mode
are the main ones.  OSX adds another twist in that there is
additional animation even in  "thermometer" mode (this is what
the ttk::progressbar -phase option is there for).

Sometimes a progress bar isn't a bar at all -- many OSX
programs use a spinning "asynchronous progress indicator" or
"chasing arrows" when space is tight.  Web browsers often use
animated throbbers that also serve a branding function (e.g.,
the throbbing Netscape/MSIE/Mozilla/Firefox logo in the upper
right corner).  Many Windows applications use simple
animations like the "copying files" or "moving to trash"
dialogs.

Animations and branded throbbers aside, Windows applications
tend to use "cylon" feedback for both indeterminate and autoincrement
modes, and never use "barberpole" feedback.  OSX apps on the other
hand don't seem to use "cylon" feedback at all; from what
I've seen they only use "thermometer" and constant-rate
"barberpole" feedback (at least in bar-shaped progress bars).

So: in keeping with the idea of separating function from
appearance, the ttk::progressbar implementation leaves
it up to the theme whether to use "cylon" or "barberpole"
feedback.  It bounces the "*.pbar" element (if present) back 
and forth based on the current -value for cylons, and it 
autoincrements the -phase option for barberpoles and auxilliary 
animation.

All of the current themes use cylon feedback for both
indeterminate and autoincrement modes, except for the
Aqua theme, which uses barberpole feedback for both,
and the step theme, which uses a bizarre combination of
both -- not because it should, but because it can.
(Actually this is mostly because I needed a way to
check if -phase updates were working correctly...)


--Joe English

  jen...@fl...