3 files changed, 66 insertions, 34 deletions
diff --git a/index.js b/index.js
index b619e1b..ab80f47 100644
--- a/index.js
+++ b/index.js
@@ -1,2 +1,2 @@
-export { default as pan } from './src/modules/pan.js';
+export { default as pan, manualPan } from './src/modules/pan.js';
 export { default as zoom } from './src/modules/zoom.js';
diff --git a/src/modules/pan.js b/src/modules/pan.js
index 6f2cacf..4fcb416 100644
--- a/src/modules/pan.js
+++ b/src/modules/pan.js
@@ -2,6 +2,10 @@ import getComputedTransformMatrix from './utils.js';
 
 const minDistanceThreshold = 5;
 
+function mainButtonPressed(e) {
+  return e.button === 0;
+}
+
 function distanceBetween({ x: x1, y: y1 }, { x: x2, y: y2 }) {
   return Math.sqrt((x2 - x1) ** 2 + (y2 - y1) ** 2);
 }
@@ -20,15 +24,26 @@ function getTranslateMatrix(startPt, movePt) {
   return translateMatrix.translate(movePt.x - startPt.x, movePt.y - startPt.y);
 }
 
-export default function (svg, el, e) {
-  e.preventDefault();
+export function manualPan(gb, counter) {
+  const mtx = getComputedTransformMatrix(gb);
+  const inverseScreenCTM = gb.getScreenCTM().inverse();
 
-  const mtx = getComputedTransformMatrix(el),
-    inverseScreenCTM = el.getScreenCTM().inverse();
+  const counterRect = counter.getBoundingClientRect();
+  const mapRect = document.querySelector('object').getBoundingClientRect();
 
-  let startPt = new DOMPoint(e.clientX, e.clientY),
-    movePt = new DOMPoint(),
-    isPanning = false;
+  let startPt = new DOMPoint(counterRect.x + counterRect.width / 2, counterRect.y + counterRect.height / 2);
+  let movePt = new DOMPoint(mapRect.width / 2, mapRect.height / 2);
+
+  startPt = startPt.matrixTransform(inverseScreenCTM);
+  movePt = movePt.matrixTransform(inverseScreenCTM);
+
+  gb.style.transition = 'transform 0.5s';
+  gb.style.transform = mtx.multiply(getTranslateMatrix(startPt, movePt));
+  gb.addEventListener('transitionend', () => gb.style.transition = '', { once: true });
+}
+
+export default function (el) {
+  let mtx, inverseScreenCTM, startPt, movePt, isPanning;
 
   function pointerMove(e) {
     movePt.x = e.clientX;
@@ -36,7 +51,6 @@ export default function (svg, el, e) {
 
     if (!isPanning && minDistanceThresholdIsMet(startPt, movePt)) {
       isPanning = true;
-      e.target.setPointerCapture(e.pointerId);
 
       startPt.x = e.clientX;
       startPt.y = e.clientY;
@@ -54,11 +68,24 @@ export default function (svg, el, e) {
     }
   }
 
-  svg.addEventListener('pointermove', pointerMove);
+  return function(e) {
+    if (!mainButtonPressed(e)) return;
+    e.preventDefault();
+    e.target.setPointerCapture(e.pointerId);
+
+    isPanning = false;
+    mtx = getComputedTransformMatrix(el);
+    inverseScreenCTM = el.getScreenCTM().inverse();
 
-  svg.addEventListener(
-    'pointerup',
-    () => svg.removeEventListener('pointermove', pointerMove),
-    { once: true }
-  );
+    startPt = new DOMPoint(e.clientX, e.clientY);
+    movePt = new DOMPoint();
+
+    this.addEventListener('pointermove', pointerMove);
+
+    this.addEventListener(
+      'pointerup',
+      () => this.removeEventListener('pointermove', pointerMove),
+      { once: true }
+    );
+  }
 }
diff --git a/src/modules/zoom.js b/src/modules/zoom.js
index fc0540b..834602b 100644
--- a/src/modules/zoom.js
+++ b/src/modules/zoom.js
@@ -5,14 +5,17 @@ function zoomIn(deltaY) {
 }
 
 function getScale(e, factor) {
-  return zoomIn(e.deltaY) ? 1 + factor : 1 - factor;
+  const outMult = 1 - factor;
+  const inMult = 1 + factor / outMult
+
+  return zoomIn(e.deltaY) ? inMult : outMult;
 }
 
 function getFocalPointBeforeTransform(el, e, inverseScreenCTM) {
-  const { x, y, width, height } = el.getBoundingClientRect(),
-    pointer = (new DOMPoint(e.clientX, e.clientY)).matrixTransform(inverseScreenCTM),
-    origin = (new DOMPoint(x, y)).matrixTransform(inverseScreenCTM),
-    terminus = (new DOMPoint(x + width, y + height)).matrixTransform(inverseScreenCTM);
+  const { x, y, width, height } = el.getBoundingClientRect();
+  const pointer = (new DOMPoint(e.clientX, e.clientY)).matrixTransform(inverseScreenCTM);
+  const origin = (new DOMPoint(x, y)).matrixTransform(inverseScreenCTM);
+  const terminus = (new DOMPoint(x + width, y + height)).matrixTransform(inverseScreenCTM);
 
   return {
     x: pointer.x,
@@ -25,10 +28,10 @@ function getFocalPointBeforeTransform(el, e, inverseScreenCTM) {
 }
 
 function getFocalPointAfterTransform(el, fpBeforeTrans, inverseScreenCTM) {
-  const { x, y, width, height } = el.getBoundingClientRect(),
-    origin = (new DOMPoint(x, y)).matrixTransform(inverseScreenCTM),
-    terminus = (new DOMPoint(x + width, y + height)).matrixTransform(inverseScreenCTM),
-    relativeFocalPoint = fpBeforeTrans.relativeToImageSize;
+  const { x, y, width, height } = el.getBoundingClientRect();
+  const origin = (new DOMPoint(x, y)).matrixTransform(inverseScreenCTM);
+  const terminus = (new DOMPoint(x + width, y + height)).matrixTransform(inverseScreenCTM);
+  const relativeFocalPoint = fpBeforeTrans.relativeToImageSize;
 
   return {
     x: origin.x + (terminus.x - origin.x) * relativeFocalPoint.x,
@@ -37,13 +40,13 @@ function getFocalPointAfterTransform(el, fpBeforeTrans, inverseScreenCTM) {
 }
 
 function getTranslateMatrix(el, e, scaleMatrix) {
-  const inverseScreenCTM = el.getScreenCTM().inverse(),
-    fpBeforeTrans = getFocalPointBeforeTransform(el, e, inverseScreenCTM);
+  const inverseScreenCTM = el.getScreenCTM().inverse();
+  const fpBeforeTrans = getFocalPointBeforeTransform(el, e, inverseScreenCTM);
 
   el.style.transform = scaleMatrix;
 
-  const fpAfterTrans = getFocalPointAfterTransform(el, fpBeforeTrans, inverseScreenCTM),
-    translateMatrix = new DOMMatrix();
+  const fpAfterTrans = getFocalPointAfterTransform(el, fpBeforeTrans, inverseScreenCTM);
+  const translateMatrix = new DOMMatrix();
 
   return translateMatrix.translate(
     fpBeforeTrans.x - fpAfterTrans.x,
@@ -51,12 +54,14 @@ function getTranslateMatrix(el, e, scaleMatrix) {
   );
 }
 
-export default function (el, e, factor = 0.1) {
-  e.preventDefault();
+export default function (el, factor = 0.1) {
+  return e => {
+    e.preventDefault();
 
-  const mtx = getComputedTransformMatrix(el),
-    scale = getScale(e, factor),
-    transMtx = getTranslateMatrix(el, e, mtx.scale(scale));
+    const mtx = getComputedTransformMatrix(el);
+    const scale = getScale(e, factor);
+    const transMtx = getTranslateMatrix(el, e, mtx.scale(scale));
 
-  el.style.transform = mtx.multiply(transMtx).scale(scale);
+    el.style.transform = mtx.multiply(transMtx).scale(scale);
+  }
 }