font.java

j2me设计的界面包

/*
 * Copyright 2008 Sun Microsystems, Inc.  All Rights Reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Sun designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Sun in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
 * CA 95054 USA or visit www.sun.com if you need additional information or
 * have any questions.
 */
package com.sun.lwuit;

import java.util.Hashtable;

/**
 * A simple abstraction of platform fonts and library fonts that enables the
 * library to use more elaborate fonts unsupported by a specific device.
 * This abstraction also supports bitmap fonts using an Ant task (more details
 * about the unifier are explained in the javadoc overview document).
 * <p>A bitmap font can be created manually but that is tedious, normally you would use
 * the Ant task as illustrated bellow to produce a resource file containing
 * the supported bitmap font. For further detail read the overview document and 
 * {@link com.sun.lwuit.util.Resources}.
<pre>
&lt;target name="pre-init"&gt;
     &lt;taskdef classpath="ImageUnifier.jar" classname="com.sun.jwt.resource.Builder" name="build" /&gt;
     &lt;build dest="src/font.res"&gt;
        &lt;font src="images/arial.ttf" bold="true" italic="true" size="11" /&gt;
        &lt;font logicalName="Dialog" /&gt;
    &lt;/build&gt;
&lt;/target&gt;
</pre>
 * <p>The following attributes can be expressed for a font ant task:
 * <ul>
 * <li>name - name for the font to load from the resource file (optional: defaults to logical name or file name).
 * <li>charset - defaults to the English alphabet, numbers and common signs. 
 * Should contain a list of all characters that should be supported by a font. E.g. if a font would always be
 * used for uppercase letters then it would save space to define the charset as: {@code "ABCDEFGHIJKLMNOPQRSTUVWXYZ" }
 * <li>src - font file in the case of using a file, defaults to TrueType font
 * <li>size - floating point size of the font
 * <li>bold - defaults to false indicates if the font should be bold
 * <li>italic - defaults to false indicates if the font should be italic
 * <li>trueType - defaults to true, relevant only when src is used. If set to false type 1 fonts are assumed.
 * <li>antiAliasing - defaults to true otherwise fonts will be aliased
 * <li>logicalName - logical name of the font as specified by java.awt.Font in Java SE: 
 * {@code Dialog, DialogInput, Monospaced, Serif, or SansSerif }
 * </ul>
 */
public abstract class Font {
    /**
     * Constant allowing us to author portable system fonts
     */
    public static final int FACE_MONOSPACE = 32;

    /**
     * Constant allowing us to author portable system fonts
     */
    public static final int FACE_PROPORTIONAL = 64;

    /**
     * Constant allowing us to author portable system fonts
     */
    public static final int FACE_SYSTEM = 0;

    /**
     * Constant allowing us to author portable system fonts
     */
    public static final int SIZE_LARGE = 16;

    /**
     * Constant allowing us to author portable system fonts
     */
    public static final int SIZE_MEDIUM = 0;

    /**
     * Constant allowing us to author portable system fonts
     */
    public static final int SIZE_SMALL = 8;

    /**
     * Constant allowing us to author portable system fonts
     */
    public static final int STYLE_BOLD = 1;

    /**
     * Constant allowing us to author portable system fonts
     */
    public static final int STYLE_ITALIC = 2;
    
    /**
     * Constant allowing us to author portable system fonts
     */
    public static final int STYLE_UNDERLINED = 4;

    /**
     * Constant allowing us to author portable system fonts
     */
    public static final int STYLE_PLAIN = 0;
    
    private static Font defaultFont;
    
    private static Hashtable bitmapCache = new Hashtable();
    
    /**
     * Creates a new Font
     */
    protected Font(){
    }

    /**
     * Returns a previously loaded bitmap font from cache
     * 
     * @param fontName the font name is the logical name of the font 
     * @see #clearBitmapCache
     */
    public static Font getBitmapFont(String fontName) {
        return (Font)bitmapCache.get(fontName);
    }
    
    
    /**
     * Bitmap fonts are cached this method allows us to flush the cache thus allows
     * us to reload a font
     */
    public static void clearBitmapCache() {
        bitmapCache.clear();
    }

    /**
     * Increase the contrast of the bitmap font for rendering on top of a surface
     * whose color is darker. This is useful when drawing anti-aliased bitmap fonts using a light color
     * (e.g. white) on top of a dark surface (e.g. black), the font often breaks down if its contrast is not
     * increased due to the way alpha blending appears to the eye.
     * <p>Notice that this method only works in one way, contrast cannot be decreased
     * properly in a font and it should be cleared and reloaed with a Look and Feel switch.
     * 
     * @param value the value to increase 
     */
    public void addContrast(byte value) {
    }
    /**
     * Creates a bitmap font with the given arguments and places said font in the cache
     * 
     * @param name the name for the font in the cache
     * @param bitmap a transparency map in red and black that indicates the characters
     * @param cutOffsets character offsets matching the bitmap pixels and characters in the font 
     * @param charWidth The width of the character when drawing... this should not be confused with
     *      the number of cutOffset[o + 1] - cutOffset[o]. They are completely different
     *      since a character can be "wider" and "seep" into the next region. This is
     *      especially true with italic characters all of which "lean" outside of their 
     *      bounds.
     * @param charsets the set of characters in the font
     * @return a font object to draw bitmap fonts
     */
    public static Font createBitmapFont(String name, Image bitmap, int[] cutOffsets, int[] charWidth, String charsets) {
        Font f = createBitmapFont(bitmap, cutOffsets, charWidth, charsets);
        bitmapCache.put(name, f);
        return f;
    }
        
    /**
     * Creates a bitmap font with the given arguments
     * 
     * @param bitmap a transparency map in red and black that indicates the characters
     * @param cutOffsets character offsets matching the bitmap pixels and characters in the font 
     * @param charWidth The width of the character when drawing... this should not be confused with
     *      the number of cutOffset[o + 1] - cutOffset[o]. They are completely different
     *      since a character can be "wider" and "seep" into the next region. This is
     *      especially true with italic characters all of which "lean" outside of their 
     *      bounds.
     * @param charsets the set of characters in the font
     * @return a font object to draw bitmap fonts
     */
    public static Font createBitmapFont(Image bitmap, int[] cutOffsets, int[] charWidth, String charsets) {
        return new CustomFont(bitmap, cutOffsets, charWidth, charsets);
    }
    
    /**
     * Creates a system native font in a similar way to common MIDP fonts
     * 
     * @param face One of FACE_SYSTEM, FACE_PROPORTIONAL, FACE_MONOSPACE
     * @param style one of STYLE_PLAIN, STYLE_ITALIC, STYLE_BOLD
     * @param size One of SIZE_SMALL, SIZE_MEDIUM, SIZE_LARGE
     * @return A newly created system font instance 
     */
    public static Font createSystemFont(int face, int style, int size) {
        return new SystemFont(face, style, size);
    }
    
    /**
     * Return the width of the given characters in this font instance
     * 
     * @param ch array of characters
     * @param offset characters offsets
     * @param length characters length
     * @return the width of the given characters in this font instance
     */
    public int charsWidth(char[] ch, int offset, int length){
        int retVal = 0;
        for(int i=0; i<length; i++){
            retVal += charWidth(ch[i + offset]);
        }
        return retVal;
    }
    
    /**
     * Return the width of the given string subset in this font instance
     * 
     * @param str the given string
     * @param offset the string offset
     * @param len the len od string
     * @return the width of the given string subset in this font instance
     */
    public int substringWidth(String str, int offset, int len){
        return charsWidth(str.toCharArray(), offset, len);
    }
    
    /**
     * Return the width of the given string in this font instance
     * 
     * @param str the given string     * 
     * @return the width of the given string in this font instance
     */
    public int stringWidth(String str){
        if( str==null || str.length()==0)
            return 0;
        return substringWidth(str, 0, str.length());
    }
    
    /**
     * Return the width of the specific charcter when rendered alone
     * 
     * @param ch the specific charcter
     * @return the width of the specific charcter when rendered alone
     */
    public abstract int charWidth(char ch);
    
    /**
     * Return the total height of the font
     * 
     * @return the total height of the font
     */
    public abstract int getHeight();
    
    /**
     * Draw the given char using the current font and color in the x,y 
     * coordinates.
     * 
     * @param g the graphics object
     * @param character the given character
     * @param x the x coordinate to draw the char
     * @param y the y coordinate to draw the char
     */
    abstract void drawChar(Graphics g, char character, int x, int y);
    
    /**
     * Return the global default font instance
     * 
     * @return the global default font instance
     */
    public static Font getDefaultFont(){
        if(defaultFont == null) {
            defaultFont = SystemFont.defaultFont;
        }
        return defaultFont;
    }

    /**
     * Sets the global default font instance 
     * 
     * @param f the global default font instance 
     */
    public static void setDefaultFont(Font f) {
        if(f != null) {
            defaultFont = f;
        }
    }
    
    /**
     * Draw the given char array using the current font and color in the x,y 
     * coordinates
     * 
     * @param g the graphics object
     * @param data the given char array 
     * @param offset the offset in the given char array
     * @param length the number of chars to draw
     * @param x the x coordinate to draw the char
     * @param y the y coordinate to draw the char
     */
    void drawChars(Graphics g, char[] data, int offset, int length, int x, int y) {
        
        char c;
        for ( int i = 0; i < length; i++ ) {
            c = data[offset+i];
            drawChar(g, c, x, y);
            x += charWidth(c);
        }
    }

    /**
     * Return Optional operation returning the font face for system fonts
     * 
     * @return Optional operation returning the font face for system fonts
     */
    public int getFace(){
        return 0;
    }
    
    /**
     * Return Optional operation returning the font size for system fonts
     * 
     * @return Optional operation returning the font size for system fonts
     */
    public int getSize(){
        return 0;
    }

    /**
     * Return Optional operation returning the font style for system fonts
     * 
     * @return Optional operation returning the font style for system fonts
     */
    public int getStyle() {
        return 0;
    }
    
    /**
     * Returns a string containing all the characters supported by this font.
     * Will return null for system fonts.
     * 
     * @return String containing the characters supported by a bitmap font or
     * null otherwise.
     */
    public String getCharset() {
        return null;
    }
}