When is message passing required?

[Richard Gaskin]

Paul Dupuis wrote:
 > "Normally" (and yes that can be subjective), you expect key presses to
 > cause characters to appear or clicking in a closebox of a window to
 > close the window. If the messages corresponding to those are trapped
 > without passing the message, the event/action is not performed by the
 > engine.

There's the difference between keyDown and keyUp, and where many people 
fond of HyperCard find themselves needing to learn new things but in 
ways most of us here welcome:

LiveCode has extended the scope of its messages to provide a granularity 
unmatched by perhaps even the most comprehensive xTalk eer. Sybase Gain 
Momentum.

With LiveCode we can choose to handle either the moment before the key 
is rendered in the field (keyDown) or after (keyUp).

Both are useful of course, but for different circumstances.

But to address the original question, I don't believe I've seen a 
catalog of messages categorized by implications of passing or not 
passing.  And since the implications vary so much from message to 
message, I'm unable to conceive of what those categories might look like.

-- 
  Richard Gaskin
  Fourth World Systems
  Software Design and Development for the Desktop, Mobile, and the Web
  ____________________________________________________________________
  Ambassador at FourthWorld.com                http://www.FourthWorld.com