other.html

JSP中文介绍,对于菜鸟有用

<STRONG>Note</STRONG>:
Currently, a <CODE>TextLayout</CODE> object uses the 
Roman baseline no matter what language the text is in. Many fonts
assume the Roman baseline too, so these methods exist for typographic 
features that are not currently in widespread use. When <CODE>TextLayout</CODE>
supports the Roman, centered, and hanging baselines, you will be able to
use the 
information returned by these methods to align a line of text that
uses different baselines. 
<HR>
</BLOCKQUOTE>
<P>

<A NAME="ascent"></A>
<H3>Ascent, Descent, and Leading</H3>

Ascent, descent, and leading are properties of fonts.  The ascent
of a font is the distance from the tops of the tallest glyphs to the
baseline.
<P>
<IMG SRC="./Art/Ascent.gif">
<P>
The descent of a font is the distance from the baseline to the bottom
of the lowest descenders on the glyphs.
<P>
<IMG SRC="./Art/Descent.gif">
<P>
The leading is the recommended vertical distance from the bottom of
the descenders to the top of the next line in a multiline setting.
<P>
<IMG SRC="./Art/Leading.gif">
<P>

A <CODE>TextLayout</CODE> object has methods for returning information
about the ascent, descent, and leading of the font. If the
text string uses more than one font, the ascent and descent
are computed as the maximum values for the fonts used in the
<CODE>TextLayout</CODE> object.

<UL>
<LI><CODE>TextLayout.getAscent</CODE>
<LI><CODE>TextLayout.getDescent</CODE>
<LI><CODE>TextLayout.getLeading</CODE>
</UL>

<A NAME="advance"></A>
<H3>Advance</H3>

The advance is the length of the string in the <CODE>TextLayout</CODE>, 
which is calculated as the distance 
from the left edge of the left-most glyph to the right edge of the right-most
glyph. 
<P>
<IMG SRC="./Art/Advance.gif">
<P>
The visual advance is the length of the string in the <CODE>TextLayout</CODE>
object minus trailing whitespace.
<P>
<IMG SRC="./Art/VAdvance.gif">
<P>
A <CODE>TextLayout</CODE> object has methods for returning its advance and 
visual advance.
<UL>
<LI><CODE>TextLayout.getAdvance</CODE>
<LI><CODE>TextLayout.getVisualAdvance</CODE>
</UL>

<A NAME="bounds"></A>
<H3>Bounds</H3>

The bounding box encloses the text in the <CODE>TextLayout</CODE>
object. It includes all the visible glyphs and the caret
boundaries, some of which might hang over the origin or
origin plus advance.  
<P>
<IMG SRC="./Art/Bounds.gif">
<P>
A <CODE>TextLayout</CODE> object has methods to return its bounds and the
black box bounds for a range of characters.
The bounding box returned by <CODE>TextLayout.getBounds</CODE> is relative 
to the origin of the <CODE>TextLayout</CODE>, and not to any particular 
screen position.
<P>
The black box bounds is the union of the bounding boxes of all the glyphs
corresponding to the characters between a starting point and an ending point.
In bidirectional text, this path might be disjoint either on the display or in
the
source text. See the <A HREF="int.html#highlighting">Selection Highlighting</A>
section in Lesson 4  for information on how a range of characters in
bidirectional text is not always contiguous.

<UL>
<LI><CODE>TextLayout.getBounds</CODE>
<LI><CODE>TextLayout.getBlackBoxBounds</CODE>
</UL>

<A NAME="just"></A>
<H3>Justified Text</H3>

<CODE>TextLayout.getCharacterLevel</CODE> is not implemented yet so
you cannot justify a paragraph of text so all lines are equal in length.
However, you can right, center, or left justify
text by drawing the <CODE>TextLayout</CODE> object in a different
location computed by calling <CODE>TextLayout.getVisibleAdvance</CODE>.
<P>
The <A HREF="./Code/LineBreakSample.java">LineBreakSample.java</A> code
shows how to left-align left-to-right text and right-align right-to-left
text.  Here is how to align the other possibilities.
<P>
To right-align a left-to-right layout: Draw at 
<CODE>
(rightMargin - layout.getVisibleAdvance()).
</CODE>
<P>
<IMG SRC="./Art/rightAlign.gif">
<P>
To center a left-to-right layout: Draw at 
<CODE>
(leftMargin + rightMargin - layout.getVisibleAdvance()) / 2.
</CODE>
<P>
<IMG SRC="./Art/centerAlign.gif">
<P>
To left-align a right-to-left layout: Draw at
<CODE>
(leftMargin + (layout.getVisibleAdvance() - layout.getAdvance)).
</CODE>
<P>
To center a right-toleft layout: Draw at 
<CODE>
(leftMargin + rightMargin + layout.getAdvance ()) / 2 - layout.getAdvance().
</CODE>

<A NAME="level"></A>
<H3>Character Level</H3>

<CODE>TextLayout.getCharacterLevel</CODE> returns the bidirectional level of the 
character as computed by the bidirectional algorithm.  This is primarily used to 
determine if the character in question is a left-to-right or a right-to-left character 
(which depends on context and style information, and is not a simple character
property). The level (0-16 inclusive) is returned so clients with particular user
interface needs (for instance, clients building user interfaces
that show nested bidirectional levels in some way) have access to the full
information.
<P>

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