Added ability to change zoom using Ctrl + Scroll in Document Viewer (#…

…10964)

* Add ability to zoom using Ctrl + Scroll in PDF Viewer

* Limit zoom-out to ~1 page

Observed problems with infinite zoom-out:
- Occasional display errors (e.g. no text displayed for certain pages)
- No content can be seen if zoomed out too far, might be unclear to user what happened and that zooming in will fix problem

* Updated CHANGELOG

* Remove catch newline from formatter

* Update CHANGELOG.md

---------

Co-authored-by: Oliver Kopp <kopp.dev@gmail.com>

CHANGELOG.md

@@ -24,6 +24,7 @@ Note that this project **does not** adhere to [Semantic Versioning](https://semv
 - We added the possibility to redownload files that had been present but are no longer in the specified location. [#10848](https://github.com/JabRef/jabref/issues/10848)
 - We added the citation key pattern `[camelN]`. Equivalent to the first N words of the `[camel]` pattern.
 - We added ability to export in CFF (Citation File Format) [#10661](https://github.com/JabRef/jabref/issues/10661).
+- We added the ability to zoom in and out in the document viewer using <kbd>Ctrl</kbd> + <kbd>Scroll</kbd>. [#10964](https://github.com/JabRef/jabref/pull/10964)
 
 ### Changed
 

src/main/java/org/jabref/gui/documentviewer/DocumentViewerControl.java

@@ -14,6 +14,7 @@
 import javafx.scene.control.ProgressIndicator;
 import javafx.scene.image.Image;
 import javafx.scene.image.ImageView;
+import javafx.scene.input.ScrollEvent;
 import javafx.scene.layout.StackPane;
 import javafx.scene.shape.Rectangle;
 import javafx.util.Duration;
@@ -76,6 +77,16 @@ public void show(DocumentViewModel document) {
         flow.estimatedScrollYProperty().addListener((observable, oldValue, newValue) -> scrollY.setValue(newValue));
         scrollY.addListener((observable, oldValue, newValue) -> flow.estimatedScrollYProperty().setValue((double) newValue));
         flow.totalLengthEstimateProperty().addListener((observable, oldValue, newValue) -> scrollYMax.setValue(newValue));
+        flow.addEventFilter(ScrollEvent.SCROLL, (ScrollEvent event) -> {
+            if (event.isControlDown()) {
+                event.consume();
+                if (event.getDeltaY() > 0) {
+                    changePageWidth(100);
+                } else {
+                    changePageWidth(-100);
+                }
+            }
+        });
     }
 
     private void updateCurrentPage(ObservableList<DocumentViewerPage> visiblePages) {
@@ -128,7 +139,16 @@ private void updateSizeOfDisplayedPages() {
 
     public void changePageWidth(int delta) {
         // Assuming the current page is A4 (or has same aspect ratio)
-        setPageWidth(desiredPageDimension.getWidth(Math.sqrt(2)) + delta);
+        int newWidth = desiredPageDimension.getWidth(Math.sqrt(2)) + delta;
+        // Limit zoom out to ~1 page due to occasional display errors when zooming out further
+        int minWidth = (int) (flow.getHeight() / 2 * Math.sqrt(2));
+        if (newWidth < minWidth) {
+            if (newWidth - delta == minWidth) {  // Attempting to zoom out when already at minWidth
+                return;
+            }
+            newWidth = minWidth;
+        }
+        setPageWidth(newWidth);
     }
 
     /**