Changelog for #2246

boundary constraint logic fix

changelog.txt

@@ -7,7 +7,7 @@ OPENSEADRAGON CHANGELOG
 * DEPRECATION: Don't access the viewport's degrees property directly anymore; instead use setRotation and getRotation (#2136 @jonasengelmann)
 * New gesture: Double-click and drag to zoom (on by default for touch) (#2225 @HamzaTatheer)
 * You can now provide a pivot point when rotating the viewport (#2233 @ pearcetm)
-* Improved the constraints that keep the image in the viewer, specifically when zoomed out a lot (#2160 @joedf)
+* Improved the constraints that keep the image in the viewer, specifically when zoomed out a lot (#2160 @joedf, #2246 @pearcetm)
 * You can now provide an element for the navigator (as an alternative to an ID) (#1303 @cameronbaney, #2166 #2175 @joedf)
 * Now supporting IIIF "id" and "identifier" in addition to "@id" (#2173 @ahankinson)
 * We now delegate tile fetching and caching to the TileSource, to allow for custom tile formats (#2148 @Aiosa)

src/viewport.js

@@ -530,26 +530,20 @@ $.Viewport.prototype = {
             var horizontalThreshold, leftDx, rightDx;
             if (newBounds.width > this._contentBoundsNoRotate.width) {
                 horizontalThreshold = this.visibilityRatio * this._contentBoundsNoRotate.width;
-                leftDx = this._contentBoundsNoRotate.x - newBounds.x + horizontalThreshold;
-                rightDx = contentRight - boundsRight - horizontalThreshold;
-
-                if (rightDx > 0) {
-                    newBounds.x += rightDx;
-                } else if (leftDx < 0) {
-                    newBounds.x += leftDx;
-                }
             } else {
                 horizontalThreshold = this.visibilityRatio * newBounds.width;
-                leftDx = this._contentBoundsNoRotate.x - boundsRight + horizontalThreshold;
-                rightDx = contentRight - newBounds.x - horizontalThreshold;
-                if (horizontalThreshold > this._contentBoundsNoRotate.width) {
-                    newBounds.x += (leftDx + rightDx) / 2;
-                } else if (rightDx < 0) {
-                    newBounds.x += rightDx;
-                } else if (leftDx > 0) {
-                    newBounds.x += leftDx;
-                }
             }
+
+            leftDx = this._contentBoundsNoRotate.x - boundsRight + horizontalThreshold;
+            rightDx = contentRight - newBounds.x - horizontalThreshold;
+            if (horizontalThreshold > this._contentBoundsNoRotate.width) {
+                newBounds.x += (leftDx + rightDx) / 2;
+            } else if (rightDx < 0) {
+                newBounds.x += rightDx;
+            } else if (leftDx > 0) {
+                newBounds.x += leftDx;
+            }
+
         }
 
         if (this.wrapVertical) {
@@ -561,26 +555,20 @@ $.Viewport.prototype = {
             var verticalThreshold, topDy, bottomDy;
             if (newBounds.height > this._contentBoundsNoRotate.height) {
                 verticalThreshold = this.visibilityRatio * this._contentBoundsNoRotate.height;
-                topDy = this._contentBoundsNoRotate.y - newBounds.y + verticalThreshold;
-                bottomDy = contentBottom - boundsBottom - verticalThreshold;
-
-                if (bottomDy > 0) {
-                    newBounds.y += bottomDy;
-                } else if (topDy < 0) {
-                    newBounds.y += topDy;
-                }
-            } else {
+            } else{
                 verticalThreshold = this.visibilityRatio * newBounds.height;
-                topDy = this._contentBoundsNoRotate.y - boundsBottom + verticalThreshold;
-                bottomDy = contentBottom - newBounds.y - verticalThreshold;
-                if (verticalThreshold > this._contentBoundsNoRotate.height) {
-                    newBounds.y += (topDy + bottomDy) / 2;
-                } else if (bottomDy < 0) {
-                    newBounds.y += bottomDy;
-                } else if (topDy > 0) {
-                    newBounds.y += topDy;
-                }
             }
+
+            topDy = this._contentBoundsNoRotate.y - boundsBottom + verticalThreshold;
+            bottomDy = contentBottom - newBounds.y - verticalThreshold;
+            if (verticalThreshold > this._contentBoundsNoRotate.height) {
+                newBounds.y += (topDy + bottomDy) / 2;
+            } else if (bottomDy < 0) {
+                newBounds.y += bottomDy;
+            } else if (topDy > 0) {
+                newBounds.y += topDy;
+            }
+
         }
 
         return newBounds;