font.java

SUN官方的资料

/*
 * @(#)Font.java	1.35 02/08/14 @(#)
 *
 * Copyright (c) 1999-2002 Sun Microsystems, Inc.  All rights reserved.
 * PROPRIETARY/CONFIDENTIAL
 * Use is subject to license terms.
 */

package javax.microedition.lcdui;

/**
 * The <code>Font</code> class represents fonts and font
 * metrics. <code>Fonts</code> cannot be
 * created by applications. Instead, applications query for fonts
 * based on
 * font attributes and the system will attempt to provide a font that
 * matches
 * the requested attributes as closely as possible.
 *
 * <p> A <code>Font's</code> attributes are style, size, and face. Values for
 * attributes must be specified in terms of symbolic constants. Values for
 * the style attribute may be combined using the bit-wise
 * <code>OR</code> operator,
 * whereas values for the other attributes may not be combined. For example,
 * the value </p>
 *
 * <p> <code>
 * STYLE_BOLD | STYLE_ITALIC
 * </code> </p>
 *
 * <p> may be used to specify a bold-italic font; however </p>
 *
 * <p> <code>
 * SIZE_LARGE | SIZE_SMALL
 * </code> </p>
 *
 * <p> is illegal. </p>
 *
 * <p> The values of these constants are arranged so that zero is valid for
 * each attribute and can be used to specify a reasonable default font
 * for the system. For clarity of programming, the following symbolic
 * constants are provided and are defined to have values of zero: </p>
 *
 * <p> <ul>
 * <li> <code> STYLE_PLAIN </code> </li>
 * <li> <code> SIZE_MEDIUM </code> </li>
 * <li> <code> FACE_SYSTEM </code> </li>
 * </ul> </p>
 *
 * <p> Values for other attributes are arranged to have disjoint bit patterns
 * in order to raise errors if they are inadvertently misused (for example,
 * using <code>FACE_PROPORTIONAL</code> where a style is
 * required). However, the values
 * for the different attributes are not intended to be combined with each
 * other. </p>
 * @since MIDP 1.0
 */

public final class Font {

    /**
     * The plain style constant. This may be combined with the
     * other style constants for mixed styles. 
     *
     * <P>Value <code>0</code> is assigned to <code>STYLE_PLAIN</code>.</P>
     */
    public static final int STYLE_PLAIN = 0;
  
    /**
     * The bold style constant. This may be combined with the
     * other style constants for mixed styles.
     *
     * <P>Value <code>1</code> is assigned to <code>STYLE_BOLD</code>.</P>
     */
    public static final int STYLE_BOLD = 1;
  
    /**
     * The italicized style constant. This may be combined with
     * the other style constants for mixed styles.
     *
     * <P>Value <code>2</code> is assigned to <code>STYLE_ITALIC</code>.</P>
     */
    public static final int STYLE_ITALIC = 2;
  
    /**
     * The underlined style constant. This may be combined with
     * the other style constants for mixed styles.
     *
     * <P>Value <code>4</code> is assigned to <code>STYLE_UNDERLINED</code>.</P>
     */
    public static final int STYLE_UNDERLINED = 4;
  
    /**
     * The &quot;small&quot; system-dependent font size.
     *
     * <P>Value <code>8</code> is assigned to <code>STYLE_SMALL</code>.</P>
     */
    public static final int SIZE_SMALL = 8;
  
    /**
     * The &quot;medium&quot; system-dependent font size.
     *
     * <P>Value <code>0</code> is assigned to <code>STYLE_MEDIUM</code>.</P>
     */
    public static final int SIZE_MEDIUM = 0;
  
    /**
     * The &quot;large&quot; system-dependent font size.
     *
     * <P>Value <code>16</code> is assigned to <code>SIZE_LARGE</code>.</P>
     */
    public static final int SIZE_LARGE = 16;
  
    /**
     * The &quot;system&quot; font face.
     *
     * <P>Value <code>0</code> is assigned to <code>FACE_SYSTEM</code>.</P>
     */
    public static final int FACE_SYSTEM = 0;
  
    /**
     * The &quot;monospace&quot; font face.
     *
     * <P>Value <code>32</code> is assigned to <code>FACE_MONOSPACE</code>.</P>
     */
    public static final int FACE_MONOSPACE = 32;
  
    /**
     * The &quot;proportional&quot; font face.
     *
     * <P>Value <code>64</code> is assigned to
     * <code>FACE_PROPORTIONAL</code>.</P>
     */
    public static final int FACE_PROPORTIONAL = 64;
  
    /**
     * Default font specifier used to draw Item and Screen contents.
     *
     * <code>FONT_STATIC_TEXT</code> has the value <code>0</code>.
     *
     * @see #getFont(int fontSpecifier)
     * @since MIDP 2.0
     */
    public static final int FONT_STATIC_TEXT = 0;

    /**
     * Font specifier used by the implementation to draw text input by
     * a user.
     *
     * <code>FONT_INPUT_TEXT</code> has the value <code>1</code>.
     *
     * @see #getFont(int fontSpecifier)
     * @since MIDP 2.0 
     */
    public static final int FONT_INPUT_TEXT = 1;

    /**
     * Gets the <code>Font</code> used by the high level user interface
     * for the <code>fontSpecifier</code> passed in. It should be used
     * by subclasses of
     * <code>CustomItem</code> and <code>Canvas</code> to match user
     * interface on the device.
     *
     * @param fontSpecifier one of <code>FONT_INPUT_TEXT</code>, or
     * <code>FONT_STATIC_TEXT</code>
     * @return font that corresponds to the passed in font specifier
     * @throws IllegalArgumentException if <code>fontSpecifier</code> is not 
     * a valid fontSpecifier
     * @since MIDP 2.0
     */
    public static Font getFont(int fontSpecifier) {

	Font font;

	switch (fontSpecifier) {
	case FONT_STATIC_TEXT:   // has the UE team defined RI fonts
	case FONT_INPUT_TEXT:    // for these two options? 
	    font = DEFAULT_FONT; 
	    break;
	default:
	    throw new IllegalArgumentException();
	}
	return font;
    }

    /**
     * Construct a new Font object
     *
     * @param face The face to use to construct the Font
     * @param style The style to use to construct the Font
     * @param size The point size to use to construct the Font
     */
    private Font(int face, int style, int size) {
        this.face  = face;
        this.style = style;
        this.size  = size;

        init(face, style, size);
    }

    /**
     * Gets the default font of the system.
     * @return the default font
     */
    public static Font getDefaultFont() {
        // SYNC NOTE: return of atomic value, no locking necessary
        return DEFAULT_FONT;
    }

    /**
     * Obtains an object representing a font having the specified face, style,
     * and size. If a matching font does not exist, the system will
     * attempt to provide the closest match. This method <em>always</em> 
     * returns
     * a valid font object, even if it is not a close match to the request. 
     *
     * @param face one of <code>FACE_SYSTEM</code>,
     * <code>FACE_MONOSPACE</code>, or <code>FACE_PROPORTIONAL</code>
     * @param style <code>STYLE_PLAIN</code>, or a combination of
     * <code>STYLE_BOLD</code>,
     * <code>STYLE_ITALIC</code>, and <code>STYLE_UNDERLINED</code>
     * @param size one of <code>SIZE_SMALL</code>, <code>SIZE_MEDIUM</code>,
     * or <code>SIZE_LARGE</code>
     * @return instance the nearest font found
     * @throws IllegalArgumentException if <code>face</code>, 
     * <code>style</code>, or <code>size</code> are not
     * legal values
     */
    public static Font getFont(int face, int style, int size) {
        if ((face != FACE_SYSTEM) 
            && (face != FACE_MONOSPACE)
            && (face != FACE_PROPORTIONAL)) {
            throw new IllegalArgumentException("Unsupported face");
        }

        if ((style & ((STYLE_UNDERLINED << 1) - 1)) != style) {
            throw new IllegalArgumentException("Illegal style");
        }

        if ((size != SIZE_SMALL) 
            && (size != SIZE_MEDIUM)
            && (size != SIZE_LARGE)) {