From 517c0099ce72299ffb350423332a9fccf60a8ab3 Mon Sep 17 00:00:00 2001
From: Robert Kaiser <robert@widebook.box.kairo.at>
Date: Fri, 16 Aug 2013 06:38:30 +0200
Subject: [PATCH] try supporting pinch zoom in a simple way

---
 js/map.js         | 44 +++++++++++++++++++++++++++++++++++++++++++-
 manifest.appcache |  2 +-
 2 files changed, 44 insertions(+), 2 deletions(-)

diff --git a/js/map.js b/js/map.js
index 3cc00c5..2ecd3a4 100644
--- a/js/map.js
+++ b/js/map.js
@@ -61,7 +61,7 @@ var gLoadingTile;
 var gMapPrefsLoaded = false;
 
 var gDragging = false;
-var gDragTouchID;
+var gDragTouchID, gPinchStartWidth;
 
 var gGeoWatchID;
 var gTrack = [];
@@ -482,6 +482,14 @@ var mapEvHandler = {
       case "mousedown":
       case "touchstart":
         if (touchEvent) {
+          if (aEvent.targetTouches.length == 2) {
+            gPinchStartWidth = Math.sqrt(
+                Math.pow(aEvent.targetTouches.item(1).clientX -
+                         aEvent.targetTouches.item(0).clientX, 2) +
+                Math.pow(aEvent.targetTouches.item(1).clientY -
+                         aEvent.targetTouches.item(0).clientY, 2)
+            );
+          }
           gDragTouchID = aEvent.changedTouches.item(0).identifier;
           coordObj = aEvent.changedTouches.identifiedTouch(gDragTouchID);
         }
@@ -497,6 +505,40 @@ var mapEvHandler = {
         break;
       case "mousemove":
       case "touchmove":
+        if (touchEvent && aEvent.targetTouches.length == 2) {
+          curPinchStartWidth = Math.sqrt(
+              Math.pow(aEvent.targetTouches.item(1).clientX -
+                       aEvent.targetTouches.item(0).clientX, 2) +
+              Math.pow(aEvent.targetTouches.item(1).clientY -
+                       aEvent.targetTouches.item(0).clientY, 2)
+          );
+          if (gPinchStartWidth / curPinchStartWidth > 1.7 ||
+              gPinchStartWidth / curPinchStartWidth < 0.6) {
+            var newZoomLevel = gPos.z + (gPinchStartWidth < curPinchStartWidth ? 1 : -1);
+            if ((newZoomLevel >= 0) && (newZoomLevel <= gMaxZoom)) {
+              // Calculate new center of the map - preserve middle of pinch.
+              // This means that pixel distance between old center and middle
+              // must equal pixel distance of new center and middle.
+              var x = (aEvent.targetTouches.item(1).clientX +
+                       aEvent.targetTouches.item(0).clientX) / 2 -
+                      gMapCanvas.offsetLeft;
+              var y = (aEvent.targetTouches.item(1).clientY +
+                       aEvent.targetTouches.item(0).clientY) / 2 -
+                      gMapCanvas.offsetTop;
+
+              // Zoom factor after this action.
+              var newZoomFactor = Math.pow(2, gMaxZoom - newZoomLevel);
+              gPos.x -= (x - gMapCanvas.width / 2) * (newZoomFactor - gZoomFactor);
+              gPos.y -= (y - gMapCanvas.height / 2) * (newZoomFactor - gZoomFactor);
+
+              if (gPinchStartWidth < curPinchStartWidth)
+                zoomIn();
+              else
+                zoomOut();
+            }
+          }
+          break;
+        }
         var x = coordObj.clientX - gMapCanvas.offsetLeft;
         var y = coordObj.clientY - gMapCanvas.offsetTop;
         if (gDragging === true) {
diff --git a/manifest.appcache b/manifest.appcache
index cdbbc5a..ef33d92 100644
--- a/manifest.appcache
+++ b/manifest.appcache
@@ -1,6 +1,6 @@
 CACHE MANIFEST
 
-# 2013-07-07
+# 2013-08-15
 manifest.webapp
 js/map.js
 js/ui.js
-- 
2.35.3