Using tiles.

src/components/map/map.tsx

@@ -2,6 +2,13 @@ import react, { useMemo, useEffect } from 'react';
 import { useDispatch, useSelector } from 'react-redux';
 import _ from 'lodash';
 import { MapState, mapActions } from '../../store/map';
+import { slippyActions } from '../../store/slippy';
+import { lat2tile, lon2tile } from '../../lib/geo';
+import Tile from './tile';
+
+import '../../theme/map.css';
+
+export const tileSize = 256;
 
 const Map: react.FC<{}> = (props: {}) => {
   const dispatch = useDispatch();
@@ -22,86 +29,43 @@ const Map: react.FC<{}> = (props: {}) => {
     window.addEventListener('resize', debouncedResizeHandler);
   }, []);
 
+  const nbTilesY = _.ceil(mapState.viewport.height / tileSize) + 3;
+  const nbTilesX = _.ceil(mapState.viewport.width / tileSize) + 3;
+  const [tileCenterY, reminderY] = lat2tile(
+    mapState.scope.center.lat,
+    mapState.scope.zoom
+  );
+  const [tileCenterX, reminderX] = lon2tile(
+    mapState.scope.center.lon,
+    mapState.scope.zoom
+  );
+  const firstTileY = tileCenterY - _.round(nbTilesY / 2);
+  const firstTileX = tileCenterX - _.round(nbTilesX / 2);
+  const locationY = (tileCenterY + reminderY - firstTileY) * tileSize;
+  const locationX = (tileCenterX + reminderX - firstTileX) * tileSize;
+  const targetLocationY = mapState.viewport.height / 2;
+  const targetLocationX = mapState.viewport.width / 2;
+  const deltaY = targetLocationY - locationY;
+  const deltaX = targetLocationX - locationX;
+
+  dispatch(slippyActions.set({ scale: 1, translation: { x: deltaX, y: deltaY } }));
+
   return (
-    <div>
+    <div className='tiles'>
-      <div style={{ height: '256px' }}>
+      {_.range(nbTilesY).map((iy) => (
-        <img
+        <div key={'y' + iy} className='tilesRow'>
-          alt=''
+          {_.range(nbTilesX).map((ix) => (
-          role='presentation'
+            <Tile
-          src='https://tile.openstreetmap.org/14/11720/10052.png'
+              key={'x' + ix + 'y' + iy}
-          style={{ width: '256px', height: '256px', opacity: 1 }}
+              iy={iy}
-        />
+              ix={ix}
-        <img
+              x={firstTileX + ix}
-          alt=''
+              y={firstTileY + iy}
-          role='presentation'
+              zoom={mapState.scope.zoom}
-          src='https://tile.openstreetmap.org/14/11721/10052.png'
+            />
-          style={{ width: '256px', height: '256px', opacity: 1 }}
+          ))}
-        />
+        </div>
-        <img
+      ))}
-          alt=''
-          role='presentation'
-          src='https://tile.openstreetmap.org/14/11722/10052.png'
-          style={{ width: '256px', height: '256px', opacity: 1 }}
-        />
-        <img
-          alt=''
-          role='presentation'
-          src='https://tile.openstreetmap.org/14/11723/10052.png'
-          style={{ width: '256px', height: '256px', opacity: 1 }}
-        />
-      </div>
-      <div style={{ height: '256px' }}>
-        <img
-          alt=''
-          role='presentation'
-          src='https://tile.openstreetmap.org/14/11720/10053.png'
-          style={{ width: '256px', height: '256px', opacity: 1 }}
-        />
-        <img
-          alt=''
-          role='presentation'
-          src='https://tile.openstreetmap.org/14/11721/10053.png'
-          style={{ width: '256px', height: '256px', opacity: 1 }}
-        />
-        <img
-          alt=''
-          role='presentation'
-          src='https://tile.openstreetmap.org/14/11722/10053.png'
-          style={{ width: '256px', height: '256px', opacity: 1 }}
-        />
-        <img
-          alt=''
-          role='presentation'
-          src='https://tile.openstreetmap.org/14/11723/10053.png'
-          style={{ width: '256px', height: '256px', opacity: 1 }}
-        />
-      </div>
-      <div style={{ height: '256px' }}>
-        <img
-          alt=''
-          role='presentation'
-          src='https://tile.openstreetmap.org/14/11720/10054.png'
-          style={{ width: '256px', height: '256px', opacity: 1 }}
-        />
-        <img
-          alt=''
-          role='presentation'
-          src='https://tile.openstreetmap.org/14/11721/10054.png'
-          style={{ width: '256px', height: '256px', opacity: 1 }}
-        />
-        <img
-          alt=''
-          role='presentation'
-          src='https://tile.openstreetmap.org/14/11722/10054.png'
-          style={{ width: '256px', height: '256px', opacity: 1 }}
-        />
-        <img
-          alt=''
-          role='presentation'
-          src='https://tile.openstreetmap.org/14/11723/10054.png'
-          style={{ width: '256px', height: '256px', opacity: 1 }}
-        />
-      </div>
     </div>
   );
 };

src/components/map/tile.tsx

@@ -0,0 +1,29 @@
+import React from 'react';
+import { tileSize } from './map';
+
+const tileProvider = (zoom: number, x: number, y: number) =>
+  'https://tile.openstreetmap.org/' + zoom + '/' + x + '/' + y + '.png';
+
+const Tile: React.FC<{
+  ix: number;
+  iy: number;
+  x: number;
+  y: number;
+  zoom: number;
+}> = (props: {
+  ix: number;
+  iy: number;
+  x: number;
+  y: number;
+  zoom: number;
+}) => {
+  return (
+    <img
+      src={tileProvider(props.zoom, props.x, props.y)}
+      className='tile'
+      alt=''
+    />
+  );
+};
+
+export default Tile;

src/components/slippy/slippy.tsx

@@ -9,21 +9,6 @@ import WheelHandler from './wheel-handler';
 import { useSelector } from 'react-redux';
 import { MapState } from '../../store/map';
 
-export interface Point {
-  x: number;
-  y: number;
-}
-
-export interface Translation {
-  translate: Point;
-}
-
-export interface Scale {
-  scale: {
-    center: Point;
-    factor: number;
-  };
-}
 
 const Slippy: react.FC<{}> = () => {
   //console.log(`--- Rendering viewport, props: ${JSON.stringify(props)} ---`);

src/lib/geo.ts

@@ -0,0 +1,38 @@
+
+export interface Point {
+  x: number;
+  y: number;
+}
+
+export interface geoPoint {
+  lon: number;
+  lat: number;
+}
+
+// cf https://wiki.openstreetmap.org/wiki/Slippy_map_tilenames#ECMAScript_(JavaScript/ActionScript,_etc.)
+export const lon2tile = (lon: number, zoom: number) => {
+  const real = ((lon + 180) / 360) * Math.pow(2, zoom);
+  const floor = Math.floor(real);
+  return [floor, real - floor];
+};
+export const lat2tile = (lat: number, zoom: number) => {
+  const real =
+    ((1 -
+      Math.log(
+        Math.tan((lat * Math.PI) / 180) + 1 / Math.cos((lat * Math.PI) / 180)
+      ) /
+        Math.PI) /
+      2) *
+    Math.pow(2, zoom);
+  const floor = Math.floor(real);
+  return [floor, real - floor];
+};
+
+export function tile2long(x: number, z: number) {
+  return (x / Math.pow(2, z)) * 360 - 180;
+}
+
+export function tile2lat(y: number, z: number) {
+  var n = Math.PI - (2 * Math.PI * y) / Math.pow(2, z);
+  return (180 / Math.PI) * Math.atan(0.5 * (Math.exp(n) - Math.exp(-n)));
+}

src/store/map.ts

@@ -1,10 +1,15 @@
 import { createSlice } from '@reduxjs/toolkit';
+import { geoPoint } from '../lib/geo';
 
 export interface MapState {
   viewport: {
     width: number;
     height: number;
   };
+  scope: {
+    center: geoPoint;
+    zoom: number;
+  };
 }
 
 const initialMapState: MapState = {
@@ -12,6 +17,10 @@ const initialMapState: MapState = {
     width: window.innerWidth,
     height: window.innerHeight,
   },
+  scope: {
+    center: { lat: -37.8372, lon: 77.5513 },
+    zoom: 13,
+  },
 };
 
 const mapSlice = createSlice({
@@ -19,8 +28,8 @@ const mapSlice = createSlice({
   initialState: initialMapState,
   reducers: {
     resize: (state) => {
-        state.viewport.height = window.innerHeight;
+      state.viewport.height = window.innerHeight;
-        state.viewport.width = window.innerWidth;
+      state.viewport.width = window.innerWidth;
     },
   },
 });

src/store/slippy.ts

@@ -1,6 +1,7 @@
+import { actionSheetController } from '@ionic/core';
 import { createSlice } from '@reduxjs/toolkit';
 
-import { Point } from '../components/slippy/slippy';
+import { Point } from '../lib/geo';
 
 export interface SlippyState {
   scale: number;
@@ -16,7 +17,7 @@ const slippySlice = createSlice({
   name: 'slippy',
   initialState: initialSlippyState,
   reducers: {
-    scale(state, action) {
+    scale: (state, action) => {
       console.log(`redux scale: ${JSON.stringify(action.payload)}`);
       state.scale = state.scale * action.payload.factor;
       state.translation.x =
@@ -28,11 +29,14 @@ const slippySlice = createSlice({
         (state.translation.y - action.payload.center.y) *
           (action.payload.factor - 1);
     },
-    translate(state, action) {
+    translate: (state, action) => {
       console.log(`redux translate: action=${JSON.stringify(action)}`);
       state.translation.x = state.translation.x + action.payload.x;
       state.translation.y = state.translation.y + action.payload.y;
     },
+    set: (state, action) => {
+      return action.payload;
+    },
   },
 });
 

src/theme/map.css

@@ -0,0 +1,8 @@
+.tilesRow {
+  height: 256px;
+}
+
+.tile {
+  height: 256px;
+  width: 256px;
+}