abstractregionpainter.java

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            return ((y-1) * centerHeight) + topHeight;
        } else if (y >= 2 && y <= 3) {
            return ((y-2) * bottomHeight) + topHeight + centerHeight;
        } else {
            throw new AssertionError("Invalid y");
        }
    }

    /**
     * Decodes and returns a float value representing the actual pixel location for
     * the anchor point given the encoded X value of the control point, and the offset
     * distance to the anchor from that control point.
     *
     * @param x an encoded x value of the bezier control point (0...1, or 1...2, or 2...3)
     * @param dx the offset distance to the anchor from the control point x
     * @return the decoded x location of the control point
     */
    protected final float decodeAnchorX(float x, float dx) {
        if (ctx.canvasSize == null) return x + dx;

        if (x >= 0 && x <= 1) {
            return decodeX(x) + (dx * leftScale);
        } else if (x > 1 && x < 2) {
            return decodeX(x) + (dx * centerHScale);
        } else if (x >= 2 && x <= 3) {
            return decodeX(x) + (dx * rightScale);
        } else {
            throw new AssertionError("Invalid x");
        }
    }

    /**
     * Decodes and returns a float value representing the actual pixel location for
     * the anchor point given the encoded Y value of the control point, and the offset
     * distance to the anchor from that control point.
     *
     * @param y an encoded y value of the bezier control point (0...1, or 1...2, or 2...3)
     * @param dy the offset distance to the anchor from the control point y
     * @return the decoded y position of the control point
     */
    protected final float decodeAnchorY(float y, float dy) {
        if (ctx.canvasSize == null) return y + dy;

        if (y >= 0 && y <= 1) {
            return decodeY(y) + (dy * topScale);
        } else if (y > 1 && y < 2) {
            return decodeY(y) + (dy * centerVScale);
        } else if (y >= 2 && y <= 3) {
            return decodeY(y) + (dy * bottomScale);
        } else {
            throw new AssertionError("Invalid y");
        }
    }

    /**
     * Decodes and returns a color, which is derived from a base color in UI
     * defaults.
     *
     * @param key     A key corrosponding to the value in the UI Defaults table
     *                of UIManager where the base color is defined
     * @param hOffset The hue offset used for derivation.
     * @param sOffset The saturation offset used for derivation.
     * @param bOffset The brightness offset used for derivation.
     * @param aOffset The alpha offset used for derivation. Between 0...255
     * @return The derived color, whos color value will change if the parent
     *         uiDefault color changes.
     */
    protected final Color decodeColor(String key, float hOffset, float sOffset,
                                      float bOffset, int aOffset) {
        if (UIManager.getLookAndFeel() instanceof NimbusLookAndFeel){
            NimbusLookAndFeel laf = (NimbusLookAndFeel) UIManager.getLookAndFeel();
            return laf.getDerivedColor(key, hOffset, sOffset, bOffset, aOffset, true);
        } else {
            // can not give a right answer as painter sould not be used outside
            // of nimbus laf but do the best we can
            return Color.getHSBColor(hOffset,sOffset,bOffset);
        }
    }

    /**
     * Decodes and returns a color, which is derived from a offset between two
     * other colors.
     *
     * @param color1   The first color
     * @param color2   The second color
     * @param midPoint The offset between color 1 and color 2, a value of 0.0 is
     *                 color 1 and 1.0 is color 2;
     * @return The derived color
     */
    protected final Color decodeColor(Color color1, Color color2,
                                      float midPoint) {
        return new Color(deriveARGB(color1, color2, midPoint));
    }
    
    /**
     * Given parameters for creating a LinearGradientPaint, this method will
     * create and return a linear gradient paint. One primary purpose for this
     * method is to avoid creating a LinearGradientPaint where the start and
     * end points are equal. In such a case, the end y point is slightly
     * increased to avoid the overlap.
     * 
     * @param x1
     * @param y1
     * @param x2
     * @param y2
     * @param midpoints
     * @param colors
     * @return a valid LinearGradientPaint. This method never returns null.
     */
    protected final LinearGradientPaint decodeGradient(float x1, float y1, float x2, float y2, float[] midpoints, Color[] colors) {
        if (x1 == x2 && y1 == y2) {
            y2 += .00001f;
        }
        return new LinearGradientPaint(x1, y1, x2, y2, midpoints, colors);
    }

    /**
     * Given parameters for creating a RadialGradientPaint, this method will
     * create and return a radial gradient paint. One primary purpose for this
     * method is to avoid creating a RadialGradientPaint where the radius
     * is non-positive. In such a case, the radius is just slightly
     * increased to avoid 0.
     * 
     * @param x
     * @param y
     * @param r
     * @param midpoints
     * @param colors
     * @return a valid RadialGradientPaint. This method never returns null.
     */
    protected final RadialGradientPaint decodeRadialGradient(float x, float y, float r, float[] midpoints, Color[] colors) {
        if (r == 0f) {
            r = .00001f;
        }
        return new RadialGradientPaint(x, y, r, midpoints, colors);
    }

    /**
     * Get a color property from the given JComponent. First checks for a
     * <code>getXXX()</code> method and if that fails checks for a client
     * property with key <code>property</code>. If that still fails to return
     * a Color then <code>defaultColor</code> is returned.
     * 
     * @param c The component to get the color property from
     * @param property The name of a bean style property or client property
     * @param defaultColor The color to return if no color was obtained from
     *        the component.
     * @return The color that was obtained from the component or defaultColor
     */
    protected final Color getComponentColor(JComponent c, String property,
                                            Color defaultColor,
                                            float saturationOffset,
                                            float brightnessOffset,
                                            int alphaOffset) {
        Color color = null;
        if (c != null) {
            // handle some special cases for performance
            if ("background".equals(property)) {
                color = c.getBackground();
            } else if ("foreground".equals(property)) {
                color = c.getForeground();
            } else if (c instanceof JList && "selectionForeground".equals(property)) {
                color = ((JList) c).getSelectionForeground();
            } else if (c instanceof JList && "selectionBackground".equals(property)) {
                color = ((JList) c).getSelectionBackground();
            } else if (c instanceof JTable && "selectionForeground".equals(property)) {
                color = ((JTable) c).getSelectionForeground();
            } else if (c instanceof JTable && "selectionBackground".equals(property)) {
                color = ((JTable) c).getSelectionBackground();
            } else {
                String s = "get" + Character.toUpperCase(property.charAt(0)) + property.substring(1);
                try {
                    Method method = c.getClass().getMethod(s);
                    color = (Color) method.invoke(c);
                } catch (Exception e) {
                    //don't do anything, it just didn't work, that's all.
                    //This could be a normal occurance if you use a property
                    //name referring to a key in clientProperties instead of
                    //a real property
                }
                if (color == null) {
                    Object value = c.getClientProperty(property);
                    if (value instanceof Color) {
                        color = (Color) value;
                    }
                }
            }
        }
        // we return the defaultColor if the color found is null, or if
        // it is a UIResource. This is done because the color for the
        // ENABLED state is set on the component, but you don't want to use
        // that color for the over state. So we only respect the color
        // specified for the property if it was set by the user, as opposed
        // to set by us.
        if (color == null || color instanceof UIResource) {
            return defaultColor;
        } else if (saturationOffset != 0 || brightnessOffset != 0 || alphaOffset != 0) {
            float[] tmp = Color.RGBtoHSB(color.getRed(), color.getGreen(), color.getBlue(), null);
            tmp[1] = clamp(tmp[1] + saturationOffset);
            tmp[2] = clamp(tmp[2] + brightnessOffset);
            int alpha = clamp(color.getAlpha() + alphaOffset);
            return new Color((Color.HSBtoRGB(tmp[0], tmp[1], tmp[2]) & 0xFFFFFF) | (alpha <<24));
        } else {
            return color;
        }
    }
    
    /**
     * A class encapsulating state useful when painting. Generally, instances of this
     * class are created once, and reused for each paint request without modification.
     * This class contains values useful when hinting the cache engine, and when decoding
     * control points and bezier curve anchors.
     */
    protected static class PaintContext {
        protected static enum CacheMode {
            NO_CACHING, FIXED_SIZES, NINE_SQUARE_SCALE
        }

        private static Insets EMPTY_INSETS = new Insets(0, 0, 0, 0);

        private Insets stretchingInsets;
        private Dimension canvasSize;
        private boolean inverted;
        private CacheMode cacheMode;
        private double maxHorizontalScaleFactor;
        private double maxVerticalScaleFactor;

        private float a; // insets.left
        private float b; // canvasSize.width - insets.right
        private float c; // insets.top
        private float d; // canvasSize.height - insets.bottom;
        private float aPercent; // only used if inverted == true
        private float bPercent; // only used if inverted == true
        private float cPercent; // only used if inverted == true
        private float dPercent; // only used if inverted == true

        /**
         * Creates a new PaintContext which does not attempt to cache or scale any cached
         * images.
         *