From 19ade7d76d43ef991a11079c1c7bf9c29565dcef Mon Sep 17 00:00:00 2001
From: Ian Gilman <ian@iangilman.com>
Date: Wed, 11 Mar 2015 15:41:36 -0700
Subject: [PATCH] Improved zoom and pan constraints

---
 src/viewport.js         |  4 +-
 test/demo/m2/js/main.js | 84 ++++++++++++++++++++++++++++++-----------
 test/demo/m2/js/page.js | 25 ++++++++++++
 3 files changed, 89 insertions(+), 24 deletions(-)

diff --git a/src/viewport.js b/src/viewport.js
index b6b57e27..ff91ad29 100644
--- a/src/viewport.js
+++ b/src/viewport.js
@@ -596,8 +596,8 @@ $.Viewport.prototype = /** @lends OpenSeadragon.Viewport.prototype */{
             return this.zoomTo(newZoom, null, true);
         }
 
-        if (Math.abs(newZoom - oldZoom) < 0.00000000001 ||
-                Math.abs(newBounds.width - oldBounds.width) < 0.00000000001) {
+        if (Math.abs(newZoom - oldZoom) < 0.00000001 ||
+                Math.abs(newBounds.width - oldBounds.width) < 0.00000001) {
             return this.panTo( center, immediately );
         }
 
diff --git a/test/demo/m2/js/main.js b/test/demo/m2/js/main.js
index 20c0cbf1..75337fdb 100644
--- a/test/demo/m2/js/main.js
+++ b/test/demo/m2/js/main.js
@@ -57,7 +57,11 @@
                 }
             });
 
-            this.viewer.addHandler('viewport-change', function(event) {
+            this.viewer.addHandler('zoom', function(event) {
+                self.applyConstraints();
+            });
+
+            this.viewer.addHandler('pan', function(event) {
                 self.applyConstraints();
             });
 
@@ -291,33 +295,69 @@
                 return;
             }
 
-            if (this.panBounds) {
-                var center = this.viewer.viewport.getCenter(true);
-                var viewBounds = this.viewer.viewport.getBounds(true);
-                var bounds = this.panBounds.clone();
-                var left = bounds.x + (viewBounds.width / 2);
-                var top = bounds.y + (viewBounds.height / 2);
-                var right = (bounds.x + bounds.width) - (viewBounds.width / 2);
-                var bottom = (bounds.y + bounds.height) - (viewBounds.height / 2);
+            if (this.panBounds && !this.inZoomConstraints) {
+                var changed = false;
+                var viewBounds = this.viewer.viewport.getBounds();
+                var panBounds = this.panBounds.clone();
 
-                var x;
-                if (left <= right) {
-                    x = Math.max(left, Math.min(right, center.x));
-                } else {
-                    x = bounds.x + (bounds.width / 2);
+                if (viewBounds.x < panBounds.x - 0.00001) {
+                    viewBounds.x = panBounds.x;
+                    changed = true;
                 }
 
-                var y;
-                if (top <= bottom) {
-                    y = Math.max(top, Math.min(bottom, center.y));
-                } else {
-                    y = bounds.y + (bounds.height / 2);
+                if (viewBounds.y < panBounds.y - 0.00001) {
+                    viewBounds.y = panBounds.y;
+                    changed = true;
                 }
 
-                if (x !== center.x || y !== center.y) {
-                    this.viewer.viewport.centerSpringX.current.value = x;
-                    this.viewer.viewport.centerSpringY.current.value = y;
+                if (viewBounds.width > panBounds.width + 0.00001) {
+                    viewBounds.width = panBounds.width;
+                    changed = true;
                 }
+
+                if (viewBounds.height > panBounds.height + 0.00001) {
+                    viewBounds.height = panBounds.height;
+                    changed = true;
+                }
+
+                if (viewBounds.x + viewBounds.width > panBounds.x + panBounds.width + 0.00001) {
+                    viewBounds.x = (panBounds.x + panBounds.width) - viewBounds.width;
+                    changed = true;
+                }
+
+                if (viewBounds.y + viewBounds.height > panBounds.y + panBounds.height + 0.00001) {
+                    viewBounds.y = (panBounds.y + panBounds.height) - viewBounds.height;
+                    changed = true;
+                }
+
+                if (changed) {
+                    this.inZoomConstraints = true;
+                    this.viewer.viewport.fitBounds(viewBounds);
+                    this.inZoomConstraints = false;
+                }
+            }
+
+            var zoom = this.viewer.viewport.getZoom();
+            var maxZoom = 2;
+
+            var zoomPoint = this.viewer.viewport.zoomPoint || this.viewer.viewport.getCenter();
+            var info = this.hitTest(zoomPoint);
+            if (info) {
+                var page = this.pages[info.index];
+                var tiledImage = page.hitTest(zoomPoint);
+                if (tiledImage) {
+                    maxZoom = this.viewer.maxZoomLevel;
+                    if (!maxZoom) {
+                        var imageWidth = tiledImage.getContentSize().x;
+                        var viewerWidth = this.$el.width();
+                        maxZoom = imageWidth * this.viewer.maxZoomPixelRatio / viewerWidth;
+                        maxZoom /= tiledImage.getBounds().width;
+                    }
+                }
+            }
+
+            if (zoom > maxZoom) {
+                this.viewer.viewport.zoomSpring.target.value = maxZoom;
             }
         },
 
diff --git a/test/demo/m2/js/page.js b/test/demo/m2/js/page.js
index a8654fd0..736cb2f1 100644
--- a/test/demo/m2/js/page.js
+++ b/test/demo/m2/js/page.js
@@ -105,6 +105,31 @@
             });
         },
 
+        // ----------
+        hitTest: function(pos) {
+            if (!this.details) {
+                return this.main.tiledImage;
+            }
+
+            var count = this.details.length;
+            var detail, box;
+
+            for (var i = 0; i < count; i++) {
+                detail = this.details[i];
+                if (!detail.tiledImage) {
+                    continue;
+                }
+
+                box = detail.tiledImage.getBounds();
+                if (pos.x > box.x && pos.y > box.y && pos.x < box.x + box.width &&
+                        pos.y < box.y + box.height) {
+                    return detail.tiledImage;
+                }
+            }
+
+            return this.main.tiledImage;
+        },
+
         // ----------
         getBounds: function() {
             return this.bounds.clone();