Refactoring.

map/src/components/double-touch-handler.tsx

@@ -2,11 +2,10 @@ import react, { useCallback, useState } from 'react';
 
 import _ from 'lodash';
 
-import { Point } from './viewport';
+import { Transformation } from './viewport';
 
 interface DoubleTouchHandlerProps {
-  updateZoom: (zoomFactor: number, center: Point) => void;
-  updateShift: (shiftDelta: Point) => void;
+  applyTransformations: (transformations: Transformation[]) => void;
   children: any;
 }
 
@@ -97,11 +96,20 @@ const DoubleTouchHandler: react.FC<DoubleTouchHandlerProps> = (
           x: (event.touches[0].pageX + event.touches[1].pageX) / 2,
           y: (event.touches[0].pageY + event.touches[1].pageY) / 2,
         };
-        props.updateZoom(factor, currentCenter);
-        // props.updateShift({
-        //   x: currentCenter.x - previousCenter.x,
-        //   y: currentCenter.y - previousCenter.y,
-        // });
+        props.applyTransformations([
+          {
+            scale: {
+              factor: factor,
+              center: currentCenter,
+            },
+          },
+          {
+            translate: {
+              x: currentCenter.x - previousCenter.x,
+              y: currentCenter.y - previousCenter.y,
+            },
+          },
+        ]);
       }
     }
   };

map/src/components/layer.tsx

@@ -1,26 +1,21 @@
 import react from 'react';
 
+import { ViewportState } from './viewport';
+
 import '../theme/layer.css';
 
 const Layer: react.FC<{
-  shift: { x: number; y: number };
-  zoom: number;
+  viewportState: ViewportState;
   children?: JSX.Element;
-}> = (props: {
-  shift: { x: number; y: number };
-  zoom: number;
-  children?: JSX.Element;
-}) => {
-  const {children: children, ...argProps} = props; 
+}> = (props: { viewportState: ViewportState; children?: JSX.Element }) => {
+  const { children: children, ...argProps } = props;
   console.log(`--- Rendering layer, props: ${JSON.stringify(argProps)} ---`);
 
   return (
     <div
       className='background'
       style={{
-        transform: `translate(${props.shift.x}px, ${props.shift.y}px) scale(${
-          props.zoom
-        })`,
+        transform: `translate(${props.viewportState.translation.x}px, ${props.viewportState.translation.y}px) scale(${props.viewportState.scale})`,
       }}
     >
       {props.children}

map/src/components/mouse-handler.tsx

@@ -2,11 +2,10 @@ import react, { useCallback, useState } from 'react';
 
 import _ from 'lodash';
 
-import { Point } from './viewport';
+import { Transformation } from './viewport';
 
 interface MouseHandlerProps {
-  updateShift: (shiftDelta: Point) => void;
-  updateZoom: (zoomFactor: number, center: Point) => void;
+  applyTransformations: (transformations: Transformation[]) => void;
   children: any;
 }
 
@@ -56,10 +55,14 @@ const MouseHandler: react.FC<MouseHandlerProps> = (
     event.preventDefault();
     if (mouseState.down) {
       genericHandler(event);
-      props.updateShift({
-        x: event.pageX - mouseState.starting.x,
-        y: event.pageY - mouseState.starting.y,
-      });
+      props.applyTransformations([
+        {
+          translate: {
+            x: event.pageX - mouseState.starting.x,
+            y: event.pageY - mouseState.starting.y,
+          },
+        },
+      ]);
       setMouseState({
         down: true,
         starting: {
@@ -77,7 +80,14 @@ const MouseHandler: react.FC<MouseHandlerProps> = (
 
   const doubleClickHandler = (event: any) => {
     genericHandler(event);
-    props.updateZoom(2, { x: event.pageX, y: event.pageY });
+    props.applyTransformations([
+      {
+        scale: {
+          factor: 2,
+          center: { x: event.pageX, y: event.pageY },
+        },
+      },
+    ]);
   };
 
   return (

map/src/components/single-touch-handler.tsx

@@ -2,10 +2,10 @@ import react, { useCallback, useState } from 'react';
 
 import _ from 'lodash';
 
-import { Point } from './viewport';
+import { Transformation } from './viewport';
 
 interface SingleTouchHandlerProps {
-  updateShift: (shiftDelta: Point) => void;
+  applyTransformations: (transformations: Transformation[]) => void;
   children: any;
 }
 
@@ -63,10 +63,14 @@ const SingleTouchHandler: react.FC<SingleTouchHandlerProps> = (
     if (touchState.state === 'pointer') {
       if (event.touches.length === 1) {
         genericHandler(event);
-        props.updateShift({
-          x:  event.touches[0].pageX - touchState.touch.x,
-          y:  event.touches[0].pageY - touchState.touch.y,
-        });
+        props.applyTransformations([
+          {
+            translate: {
+              x: event.touches[0].pageX - touchState.touch.x,
+              y: event.touches[0].pageY - touchState.touch.y,
+            },
+          },
+        ]);
         setTouchState({
           state: 'pointer',
           touch: {

map/src/components/viewport.tsx

@@ -1,6 +1,6 @@
 import react, { useCallback, useState } from 'react';
 
-import _ from 'lodash';
+import _, { constant } from 'lodash';
 
 import MouseHandler from './mouse-handler';
 import Layer from './layer';
@@ -14,48 +14,82 @@ export interface Point {
   y: number;
 }
 
+export interface Translation {
+  translate: Point;
+}
+
+export interface Scale {
+  scale: {
+    center: Point;
+    factor: number;
+  };
+}
+
+export type Transformation = Translation | Scale;
+
+// const transform1: Transformation = { translate: { x: 0, y: 1 } };
+// const transform2: Transformation = {
+//   scale: { center: { x: 10, y: 20 }, factor: 2 },
+// };
+
 interface ViewportProps {
   children: any;
 }
 
+export interface ViewportState {
+  scale: number;
+  translation: Point;
+}
+
 const Viewport: react.FC<ViewportProps> = (props: ViewportProps) => {
   //console.log(`--- Rendering viewport, props: ${JSON.stringify(props)} ---`);
 
-  const initialShitf: Point = { x: 0, y: 0 };
+  const initialState: ViewportState = { scale: 1, translation: { x: 0, y: 0 } };
 
-  const [shift, setShift] = useState(initialShitf);
-
-  const [zoom, setZoom] = useState(1);
+  const [state, setState] = useState(initialState);
 
   const genericHandler = (event: any) => {
     console.log('Log - Event: ' + event.type);
     return;
   };
 
-  // TODO: implement resize event
-  // TODO: check boundaries
-
-  const updateShift = (shiftDelta: Point) => {
-    setShift({ x: shift.x + shiftDelta.x, y: shift.y + shiftDelta.y });
-  };
-
-  const updateZoom = (zoomFactor: number, center: Point) => {
-    const newZoom = zoom * zoomFactor;
-    updateShift({
-      x: (shift.x - center.x) * (zoomFactor - 1),
-      y: (shift.y - center.y) * (zoomFactor - 1),
-    });
-    setZoom(newZoom);
+  const applyTransformations = (transformations: Transformation[]) => {
+    const newState = transformations.reduce(
+      (previousState: ViewportState, transformation): ViewportState => {
+        if ('scale' in transformation) {
+          return {
+            scale: previousState.scale * transformation.scale.factor,
+            translation: {
+              x:
+                previousState.translation.x +
+                (previousState.translation.x - transformation.scale.center.x) *
+                  (transformation.scale.factor - 1),
+              y:
+                previousState.translation.y +
+                (previousState.translation.y - transformation.scale.center.y) *
+                  (transformation.scale.factor - 1),
+            },
+          };
+        }
+        return {
+          scale: previousState.scale,
+          translation: {
+            x: previousState.translation.x + transformation.translate.x,
+            y: previousState.translation.y + transformation.translate.y,
+          },
+        };
+      },
+      state
+    );
+    setState(newState);
   };
 
   return (
     <div className='viewport'>
-      <MouseHandler updateShift={updateShift} updateZoom={updateZoom}>
-        <SingleTouchHandler updateShift={updateShift}>
-          <DoubleTouchHandler updateZoom={updateZoom} updateShift={updateShift}>
-            <Layer shift={shift} zoom={zoom}>
-              {props.children}
-            </Layer>
+      <MouseHandler applyTransformations={applyTransformations}>
+        <SingleTouchHandler applyTransformations={applyTransformations}>
+          <DoubleTouchHandler applyTransformations={applyTransformations}>
+            <Layer viewportState={state}>{props.children}</Layer>
           </DoubleTouchHandler>
         </SingleTouchHandler>
       </MouseHandler>