Re: [eclipse-incubator-e4-dev] Initial discussion onthe'modelled'workben

[Tom Schindl <tom.schindl@xxxxxxxxxxxxxxx>]

Kevin McGuire schrieb:
> Hi Tom,
>
>  >>How much CSS Browser have do we want to support? Do we for example want
>  >>to allow setting more than one style-class for an element like Browser
>  >>allow it (Pseudo SWT-HTML):
>
>  >> <tabItem class="myCTabStyle selectedMyCTabStyle">
>
>  >>In fact I think every attribute the Style-Class has must be refelected
>  >>by the UI-Element we look at or it has to hold the *clone* of style
>  >>object because modifing the background color of an UI-Widget doesn't
>  >>background color of all widgets using this style!
>
> To start I think we're fine just supporting single class CSS since it 
> covers a huge number of cases, and multiple class CSS hurts the head. 
> I'd be open to multiple though.

Support multi-classes would immediately solve e.g. activation vs 
deactivation style when the CTabItem is activated you simply add the 
secondary style and if deactivate you remove the secondary style but I 
agree that a one class is simpler for the start.

> But I don't understand the 2nd part of the question.  Can you clarify?  
>
> The properties a style-class describes must be reflected by the 
> UI-Element, although its up to us to decide how forgiving we are of this 
> (for example, typically web browsers just ignore CSS lines which set 
> attributes which aren't supported by the given HTML element).  And the 
> relationships are unidirectional, with the classes just acting as 
> selectors for applying attribute changes, but the attributes not being 
> "owned" in any way by the CSS classes.

Well this way you restore many duplicate informations on your 
UI-Elements because ~90% they are set and never changed so copying them 
on UI-Element-Creation is not a good solution in terms of memory usage.

A better approach IMHO would be to wrap on write something like this:

---------8<---------
public class UIElement {
   private Style style;

   private class WrappedStyle extends Style {
       private HashMap ownMap = new HashMap();

       private WrappedStyle(Style style) {
           this.style = style;
       }

       public String get(String name) {
          if( ownMap.contains(name) ) {
             return ownMap.get(name);
          }
       }

       public void set(String name, String value) {
          ownMap.put(name,value);
       }
   }

   // Allows reading without the need to wrap
   public String getStyleAttribute(String name) {
       return style.get(name)
   }


   public String setStyleAttribute(String name, String value) {
       getStyle().set(name,value);
   }

   public Style getStyle() {
       if( !( style instanceof WrappedStyle ) ) {
           this.style = new WrappedStyle(this.style);
       }

       return style;
   }
}
---------8<---------

This of course simplified and only doable if you have slightly 
intelligent Model-Elements.

Tom

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