refactor: buttons: Make dynamic stream color palette addition explicit.

Add comments re need to tidy palette extension & implementation details.

Author: neiljp

zulipterminal/ui_tools/buttons.py

@@ -210,16 +210,26 @@ def __init__(
  self.count = count
  self.view = view
 
+ # FIXME: This section should be moved to a general palette-extension method
+ # which is triggered when streams are initially loaded and when colors are
+ # adjusted, or new streams added
  for entry in view.palette:
  if entry[0] is None:
+ # NOTE: entry is generated at runtime, so length is dynamic
+ # entry[5] is 256-color background entry
+ # entry[2] is 16-color background entry
  background = entry[5] if len(entry) > 4 else entry[2]
  inverse_text = background if background else "black"
  break
+ # These tuples represent (new) Urwid palette entries for the stream color:
+ # (style_name, 16-color fg, 16-color bg, mono, 256+color fg, 256+color bg)
+ # The normalized color becomes a named style (eg. "#abc") for colored foreground
  view.palette.append(
- (self.color, "", "", "bold", f"{self.color}, bold", background)
+ (f"{self.color}", "", "", "bold", f"{self.color}, bold", background)
  )
+ # The s-prefixed style name (eg "s#abc") is used for inverted styling
  view.palette.append(
- ("s" + self.color, "", "", "standout", inverse_text, self.color)
+ (f"s{self.color}", "", "", "standout", inverse_text, self.color)
  )
 
  stream_marker = STREAM_ACCESS_TYPE[stream_access_type]["icon"]