[GUI] Dynamic ... something

[Wolfgang Thaller]

Axel Simon wrote:

> On Sat, Apr 12, 2003 at 06:54:13PM +0200, Wolfgang Thaller wrote:
>> None of the approaches need to be mutually exclusive, though:
>>
>> 1) Explicit placement
>> (should not be used directly except in some strange case that I just
>> can't think of)
>> 2) Platform-specific interface definition files
>> 3) Dynamic layout
>>
> I don't like the idea of separating explicit placement and dynamic 
> layout.

Explicit placement is, of course, just one very simple layout 
algorithm. I was not talking about separating it from the rest.

* Explicit placement is a layout algorithm, just like a GridBagLayout
* It is available on all platforms
* It is easy to implement on all platforms
* It is the only thing that is available on some platforms, so on those 
platforms, we'll have to implement the other algorithms on top of that
* Because it's easy to implement on all platforms, it will be useful in 
the early testing phases
* Because we need it as a base to implement better algorithms on 
Windows & Aqua, we might as well have a convenient interface to it
* It's use for laying out dialogs should, of course, be discouraged, 
for the sake of cross-platform compatibility.
* I'm sure that there are some strange situations where it is 
necessary, and if the application can query things like minimum and 
recommended sizes, font sizes are no problem

> If
> we provide a set of simple combinators, these combinators can calculate
> fixed positions for Windows and Aqua but use the widget containers 
> which
> allow resizing on Gtk and Motif.

Resizing is a different issue. Mac OS Cocoa only has explicit 
placement, but does automatic resizing.
Also, consider a document window: You'd need to place some content-area 
widget (e.g. a text widget), and two scrollbar widgets. Of course we 
need resizing, even for windows.

As I said, there is no mutual exclusion.
We should probably have good layout combinators, but we should also 
have an "explicit placement" combinator because I need it as a base to 
implement the other combinators on on Mac OS; also, it's a useful thing 
to have in some situations.

> Using combinators doesn't go along
> with absolute pixel positions anyway as far as I can tell.

I don't get that... what do you mean by this?

> I therefore opose to taking "explicit placement" as a starting
> point.

I was suggesting that we should start with explicit placement because 
it is by far the simplest mechanism; we can then already implement and 
test other parts of the CGA, before all the dynamic layout mechanisms 
are implemented on Mac OS and Windows.

Cheers,

Wolfgang