adding positionOffset prop to <Draggable/>

example/example.js

@@ -137,6 +137,11 @@ var App = React.createClass({
             {"I have a default position of {x: 25, y: 25}, so I'm slightly offset."}
           </div>
         </Draggable>
+        <Draggable positionOffset={{x: '-10%', y: '-10%'}} {...dragHandlers}>
+          <div className="box">
+            {'I have a default position based on percents {x: \'-10%\', y: \'-10%\'}, so I\'m slightly offset.'}
+          </div>
+        </Draggable>
         <Draggable position={controlledPosition} {...dragHandlers} onDrag={this.onControlledDrag}>
           <div className="box">
             My position can be changed programmatically. <br />

lib/Draggable.js

@@ -7,7 +7,7 @@ import {createCSSTransform, createSVGTransform} from './utils/domFns';
 import {canDragX, canDragY, createDraggableData, getBoundPosition} from './utils/positionFns';
 import {dontSetMe} from './utils/shims';
 import DraggableCore from './DraggableCore';
-import type {ControlPosition, DraggableBounds, DraggableCoreProps} from './DraggableCore';
+import type {ControlPosition, PositionOffsetControlPosition, DraggableBounds, DraggableCoreProps} from './DraggableCore';
 import log from './utils/log';
 import type {DraggableEventHandler} from './utils/types';
 import type {Element as ReactElement} from 'react';
@@ -28,6 +28,7 @@ export type DraggableProps = {
   defaultClassNameDragging: string,
   defaultClassNameDragged: string,
   defaultPosition: ControlPosition,
+  positionOffset: PositionOffsetControlPosition,
   position: ControlPosition,
   scale: number
 };
@@ -121,6 +122,10 @@ export default class Draggable extends React.Component<DraggableProps, Draggable
       x: PropTypes.number,
       y: PropTypes.number
     }),
+    positionOffset: PropTypes.shape({
+      x: PropTypes.oneOfType([PropTypes.number, PropTypes.string]),
+      y: PropTypes.oneOfType([PropTypes.number, PropTypes.string])
+    }),
 
     /**
      * `position`, if present, defines the current position of the element.
@@ -326,13 +331,13 @@ export default class Draggable extends React.Component<DraggableProps, Draggable
 
     // If this element was SVG, we use the `transform` attribute.
     if (this.state.isElementSVG) {
-      svgTransform = createSVGTransform(transformOpts);
+      svgTransform = createSVGTransform(transformOpts, this.props.positionOffset);
     } else {
       // Add a CSS transform to move the element around. This allows us to move the element around
       // without worrying about whether or not it is relatively or absolutely positioned.
       // If the item you are dragging already has a transform set, wrap it in a <span> so <Draggable>
       // has a clean slate.
-      style = createCSSTransform(transformOpts);
+      style = createCSSTransform(transformOpts, this.props.positionOffset);
     }
 
     const {

lib/DraggableCore.js

@@ -52,6 +52,7 @@ export type DraggableData = {
 export type DraggableEventHandler = (e: MouseEvent, data: DraggableData) => void;
 
 export type ControlPosition = {x: number, y: number};
+export type PositionOffsetControlPosition = {x: number|string, y: number|string};
 
 export type DraggableCoreProps = {
   allowAnyClick: boolean,

lib/utils/domFns.js

@@ -2,7 +2,7 @@
 import {findInArray, isFunction, int} from './shims';
 import browserPrefix, {browserPrefixToKey} from './getPrefix';
 
-import type {ControlPosition, MouseTouchEvent} from './types';
+import type {ControlPosition, PositionOffsetControlPosition, MouseTouchEvent} from './types';
 
 let matchesSelectorFunc = '';
 export function matchesSelector(el: Node, selector: string): boolean {
@@ -109,13 +109,23 @@ export function offsetXYFromParent(evt: {clientX: number, clientY: number}, offs
   return {x, y};
 }
 
-export function createCSSTransform({x, y}: {x: number, y: number}): Object {
-  // Replace unitless items with px
-  return {[browserPrefixToKey('transform', browserPrefix)]: 'translate(' + x + 'px,' + y + 'px)'};
+export function createCSSTransform(controlPos: ControlPosition, positionOffset: PositionOffsetControlPosition): Object {
+  const translation = getTranslation(controlPos, positionOffset, 'px');
+  return {[browserPrefixToKey('transform', browserPrefix)]: translation };
 }
 
-export function createSVGTransform({x, y}: {x: number, y: number}): string {
-  return 'translate(' + x + ',' + y + ')';
+export function createSVGTransform(controlPos: ControlPosition, positionOffset: PositionOffsetControlPosition): string {
+  const translation = getTranslation(controlPos, positionOffset, '');
+  return translation;
+}
+export function getTranslation({x, y}: ControlPosition, positionOffset: PositionOffsetControlPosition, unitSuffix: string): string {
+  let translation = `translate(${x}${unitSuffix},${y}${unitSuffix})`;
+  if (positionOffset) {
+    const defaultX = `${(typeof positionOffset.x === 'string') ? positionOffset.x : positionOffset.x + unitSuffix}`;
+    const defaultY = `${(typeof positionOffset.y === 'string') ? positionOffset.y : positionOffset.y + unitSuffix}`;
+    translation = `translate(${defaultX}, ${defaultY})` + translation;
+  }
+  return translation;
 }
 
 export function getTouch(e: MouseTouchEvent, identifier: number): ?{clientX: number, clientY: number} {

lib/utils/types.js

@@ -14,6 +14,7 @@ export type Bounds = {
   left: number, top: number, right: number, bottom: number
 };
 export type ControlPosition = {x: number, y: number};
+export type PositionOffsetControlPosition = {x: number|string, y: number|string};
 export type EventHandler<T> = (e: T) => void | false;
 
 // Missing in Flow

package.json

@@ -90,4 +90,4 @@
     "classnames": "^2.2.5",
     "prop-types": "^15.6.0"
   }
-}
+}

specs/draggable.spec.jsx

@@ -257,6 +257,22 @@ describe('react-draggable', function () {
       assert(style.indexOf('transform: translate(100px, 100px);') >= 0);
     });
 
+    it('should render with positionOffset set as string transform and handle subsequent translate() for DOM nodes', function () {
+      let dragged = false;
+      drag = TestUtils.renderIntoDocument(
+        <Draggable positionOffset={{x: '10%', y: '10%'}} onDrag={function() { dragged = true; }}>
+          <div />
+        </Draggable>
+      );
+
+      const node = ReactDOM.findDOMNode(drag);
+      simulateMovementFromTo(drag, 0, 0, 100, 100);
+
+      const style = node.getAttribute('style');
+      assert(dragged === true);
+      assert(style.indexOf('translate(10%, 10%) translate(100px, 100px);') >= 0);
+    });
+
     it('should honor "x" axis', function () {
       let dragged = false;
       drag = TestUtils.renderIntoDocument(