Windows, dialogs and messages
Saying something the screen itself does not say. The components here differ in one thing: how much they interrupt. A window covers the page and, when it is modal, has to be dealt with before anything else can happen. A message is a line of text that appears next to what it is about and waits to be read. A flare shows itself for a second and is gone.
The components
The overlays - a window over the page, with or without buttons:
| Component | What it is for |
|---|---|
Window |
a floating window: a title bar, a content area and nothing else |
Dialog |
the same window with a button bar and save/cancel handling |
InputDialog |
a dialog that asks for exactly one value |
MsgBox2 |
the message box: a sentence, some buttons, an answer |
ExceptionDialog |
what the user sees when code threw |
...and the things that appear inside the page itself:
| Component | What it is for |
|---|---|
ErrorPanel |
a titled block showing the messages a fence caught |
ErrorMessageDiv |
the same, as bare lines instead of a block |
MessageFlare |
a message that shows itself over the page and vanishes |
MessageLine |
one line with an icon: a remark that is part of the screen |
InfoPanel |
a paragraph of explanation with a large icon |
Explanation |
the same, with a severity |
An overlay is added to the page
Everything in the first table is a floating window, and a floating window is
added to the page, never to the ContentPanel the content lives in:
Window w = new Window("The album");
add(w); // add() on the page, not on the panel
w.add(new Para().add("...the content of the window..."));
MsgBox2 and ExceptionDialog do that themselves - MsgBox2.on(node) only
needs a node to find the page from - so for those there is nothing to add.
A window does not stop the code that opened it. The handler that made the
window runs to its end, and the window appears on the next screen the user
sees. Everything that has to happen after the user answers belongs in a
close handler, an answer handler or an onSave() - never on the line after
the window was made.
Where messages come from
The second table is only the display side. What is displayed - a UIMessage,
where it is posted, and the error fence that decides which component shows it -
is one mechanism, described in the walkthrough under
telling something to a user.
The pages here say what each component looks like and when to pick it; that page
says how a message finds them.