Refactor zooming logic out to action

This also enables a more straight-forward implementation of the functionality that the zoom buttons offer.

1 files changed, 50 insertions, 0 deletions

diff --git a/src/actions/map.js b/src/actions/map.js
index ef691873..47d4714d 100644
--- a/src/actions/map.js
+++ b/src/actions/map.js
@@ -1,3 +1,10 @@
+import {
+    MAP_MAX_SCALE,
+    MAP_MIN_SCALE,
+    MAP_SCALE_PER_EVENT,
+    MAP_SIZE_IN_PIXELS
+} from "../components/app/map/MapConstants";
+
 export const SET_MAP_POSITION = "SET_MAP_POSITION";
 export const SET_MAP_DIMENSIONS = "SET_MAP_DIMENSIONS";
 export const SET_MAP_SCALE = "SET_MAP_SCALE";
@@ -24,3 +31,46 @@ export function setMapScale(scale) {
         scale
     };
 }
+
+export function zoomInOnCenter(zoomIn) {
+    return (dispatch, getState) => {
+        const state = getState();
+
+        dispatch(zoomInOnPosition(zoomIn, state.map.dimensions.width / 2, state.map.dimensions.height / 2));
+    }
+}
+
+export function zoomInOnPosition(zoomIn, x, y) {
+    return (dispatch, getState) => {
+        const state = getState();
+
+        const centerPoint = {
+            x: x / state.map.scale - state.map.position.x / state.map.scale,
+            y: y / state.map.scale - state.map.position.y / state.map.scale,
+        };
+        const newScale = zoomIn ? state.map.scale * MAP_SCALE_PER_EVENT : state.map.scale / MAP_SCALE_PER_EVENT;
+        const boundedScale = Math.min(Math.max(MAP_MIN_SCALE, newScale), MAP_MAX_SCALE);
+
+        const newX = -(centerPoint.x - x / boundedScale) * boundedScale;
+        const newY = -(centerPoint.y - y / boundedScale) * boundedScale;
+
+        dispatch(setMapPositionWithBoundsCheck(newX, newY));
+        dispatch(setMapScale(boundedScale));
+    }
+}
+
+export function setMapPositionWithBoundsCheck(x, y) {
+    return (dispatch, getState) => {
+        const state = getState();
+
+        const scaledMapSize = MAP_SIZE_IN_PIXELS * state.map.scale;
+        const updatedX = x > 0 ? 0 :
+            (x < -scaledMapSize + state.map.dimensions.width
+                ? -scaledMapSize + state.map.dimensions.width : x);
+        const updatedY = y > 0 ? 0 :
+            (y < -scaledMapSize + state.map.dimensions.height
+                ? -scaledMapSize + state.map.dimensions.height : y);
+
+        dispatch(setMapPosition(updatedX, updatedY));
+    }
+}