 
 subsection3_5_3.html  subsection3_5_2.html  subsubsection3_5_2_1.html  tableofcontents3_1.html   Next: subsection3_5_3.html Creating Display Items Up: subsection3_5_2.html Display Items  Previous: subsubsection3_5_2_1.html Advantages of Display    Display Items and Display Styles  
The appearance of a display item is controlled by a set of
  attributes. For example, the 
text attribute controls the text
  string displayed on the item and the 
font attribute specifies
  what font should be used.
   Usually, each of the attributes falls into one of two categroies:
  ``
individual'' or ``collective''. For example, each of
  the items inside a TixTList widget may display a different text
  string; therefore we call the text string an 
individual
  attribute
. However, in most cases, the items share the same color,
  font and spacing and we call these 
collective attributes.
   One question concerns where we keep the collective attribute for the
  display items. Certainly, we can keep a 
font attribute for each
  item, but this is not really an efficient solution. In fact, if all the
  items have the same font, we would be keeping a duplicated copy of the
  same font for each of the items we create. Since a host widget may have
  many thousands of items, keeping thousands of dupilcated copys of the
  same font, or any other collective attributes, would be very wasteful.
   
To avoid the unnecessary duplication of resources, Tix stores the
  collective attributes in special objects called 
display styles. The
  relationship between display items and their styles is depicted in figure
  3-4. Each item holds its own copy of the individual
  attributes, such as 
text. However, the collective attributes are
  stored in the style objects. Each item has a special 
style  attribute that tells it which style it should use. In figure 3-4
, since items 
a and b are assigned the same
  style, therefore, they share the same font and color. Item 
c is
  assigned a different style, thus, it uses a different font than 
a  and 
b.
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