# AnchorLayout.js

    /**
     * @class Ext.layout.AnchorLayout
     * @extends Ext.layout.ContainerLayout
     * <p>This is a layout that enables anchoring of contained elements relative to the container's dimensions.  If
     * the container is resized, all anchored items are automatically rerendered according to their anchor rules.
     * This class is intended to be extended or created via the layout:'anchor' {@link Ext.Container#layout} config,
     * and should generally not need to be created directly via the new keyword.</p>
     * <p>AnchorLayout does not have any direct config options (other than inherited ones).  However, the container
     * using the AnchorLayout can supply an anchoring-specific config property of <b>anchorSize</b>.  By default,
     * AnchorLayout will calculate anchor measurements based on the size of the container itself.  However, if
     * anchorSize is specifed, the layout will use it as a virtual container for the purposes of calculating anchor
     * measurements based on it instead, allowing the container to be sized independently of the anchoring logic if necessary.</p>
     * <p>The items added to an AnchorLayout can also supply an anchoring-specific config property of <b>anchor</b> which
     * is a string containing two values: the horizontal anchor value and the vertical anchor value (for example, '100% 50%').
     * This value is what tells the layout how the item should be anchored to the container.  The following types of
     * anchor values are supported:
     * <ul>
     * <li><b>Percentage</b>: Any value between 1 and 100, expressed as a percentage.  The first anchor is the percentage
     * width that the item should take up within the container, and the second is the percentage height.  Example: '100% 50%'
     * would render an item the complete width of the container and 1/2 its height.  If only one anchor value is supplied
     * it is assumed to be the width value and the height will default to auto.</li>
     * <li><b>Offsets</b>: Any positive or negative integer value.  The first anchor is the offset from the right edge of
     * the container, and the second is the offset from the bottom edge.  Example: '-50 -100' would render an item the
     * complete width of the container minus 50 pixels and the complete height minus 100 pixels.  If only one anchor value
     * is supplied it is assumed to be the right offset value and the bottom offset will default to 0.</li>
     * <li><b>Sides</b>: Valid values are 'right' (or 'r') and 'bottom' (or 'b').  Either the container must have a fixed
     * size or an anchorSize config value defined at render time in order for these to have any effect.</li>
     * </ul>
     * <p>Anchor values can also be mixed as needed.  For example, '-50 75%' would render the width offset from the
     * container right edge by 50 pixels and 75% of the container's height.</p>
     */
    Ext.layout.AnchorLayout = Ext.extend(Ext.layout.ContainerLayout, {
        // private
        monitorResize:true,

        // private
        getAnchorViewSize : function(ct, target){
            return target.dom == document.body ?
                       target.getViewSize() : target.getStyleSize();
        },

        // private
        onLayout : function(ct, target){
            Ext.layout.AnchorLayout.superclass.onLayout.call(this, ct, target);

            var size = this.getAnchorViewSize(ct, target);

            var w = size.width, h = size.height;

            if(w < 20 || h < 20){
                return;
            }

            // find the container anchoring size
            var aw, ah;
            if(ct.anchorSize){
                if(typeof ct.anchorSize == 'number'){
                    aw = ct.anchorSize;
                }else{
                    aw = ct.anchorSize.width;
                    ah = ct.anchorSize.height;
                }
            }else{
                aw = ct.initialConfig.width;
                ah = ct.initialConfig.height;
            }

            var cs = ct.items.items, len = cs.length, i, c, a, cw, ch;
            for(i = 0; i < len; i++){
                c = cs[i];
                if(c.anchor){
                    a = c.anchorSpec;
                    if(!a){ // cache all anchor values
                        var vs = c.anchor.split(' ');
                        c.anchorSpec = a = {
                            right: this.parseAnchor(vs[0], c.initialConfig.width, aw),
                            bottom: this.parseAnchor(vs[1], c.initialConfig.height, ah)
                        };
                    }
                    cw = a.right ? this.adjustWidthAnchor(a.right(w), c) : undefined;
                    ch = a.bottom ? this.adjustHeightAnchor(a.bottom(h), c) : undefined;

                    if(cw || ch){
                        c.setSize(cw || undefined, ch || undefined);
                    }
                }
            }
        },

        // private
        parseAnchor : function(a, start, cstart){
            if(a && a != 'none'){
                var last;
                if(/^(r|right|b|bottom)$/i.test(a)){   // standard anchor
                    var diff = cstart - start;
                    return function(v){
                        if(v !== last){
                            last = v;
                            return v - diff;
                        }
                    }
                }else if(a.indexOf('%') != -1){
                    var ratio = parseFloat(a.replace('%', ''))*.01;   // percentage
                    return function(v){
                        if(v !== last){
                            last = v;
                            return Math.floor(v*ratio);
                        }
                    }
                }else{
                    a = parseInt(a, 10);
                    if(!isNaN(a)){                            // simple offset adjustment
                        return function(v){
                            if(v !== last){
                                last = v;
                                return v + a;
                            }
                        }
                    }
                }
            }
            return false;
        },

        // private
        adjustWidthAnchor : function(value, comp){
            return value;
        },

        // private
        adjustHeightAnchor : function(value, comp){
            return value;
        }

        /**
         * @property activeItem
         * @hide
         */
    });
    Ext.Container.LAYOUTS['anchor'] = Ext.layout.AnchorLayout;

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