Confusing handling of native scale layer and "zoom to download"

[GerdP]

What steps will reproduce the problem?

1. Load some data from OSM server
2. Zoom out
3. Press 5 to "zoom to download", note that a small part of the dashed area is still visible
4. Add Bing layer (or another one with a "native scale"), make sure that the "scale follows native resolution ..." checkbox is enabled, note that the dashed area disappeared because JOSM zoomed in a little bit.
5. Remove Bing layer, note that this doesn't change the map view
6. Press 5 again to zoom to download area. Note that now a large dashed area is visible, means, this zoom simply doesn't work anymore. Edit: This is also the case when the layer is not removed.

What is the expected result?

• Not sure if the small "zooom in" in step 4 is intended?
• The layer removal should restore the old behaviour befor that layer was added. So, either enable a previous layer that was used for native scaling or none.

What happens instead?

• "zoom to download" no longer works until I add another layer with "native scale" and disable the "scale follows native resolution ..." checkbox

Please provide any additional information below. Attach a screenshot if possible.

Found this while looking for memory leaks. The field NavigatableComponent.nativeScaleLayer is not modified when the Bing layer is removed.

Build-Date:2020-12-17 10:49:38
Revision:17408
Is-Local-Build:true

Identification: JOSM/1.5 (17408 SVN en) Windows 10 64-Bit
OS Build number: Windows 10 Home 2004 (19041)
Memory Usage: 791 MB / 1820 MB (671 MB allocated, but free)
Java version: 1.8.0_272-b10, AdoptOpenJDK, OpenJDK 64-Bit Server VM
Look and Feel: com.sun.java.swing.plaf.windows.WindowsLookAndFeel
Screen: \Display0 1920×1080 (scaling 1.00×1.00)
Maximum Screen Size: 1920×1080
Best cursor sizes: 16×16→32×32, 32×32→32×32
VM arguments: [-agentlib:jdwp=transport=dt_socket,suspend=y,address=localhost:57460, -ea, -javaagent:D:\eclipse-java-2020-09\eclipse\configuration\org.eclipse.osgi\215\0\.cp\lib\javaagent-shaded.jar, -Dfile.encoding=UTF-8]

Plugins:
+ ColumbusCSV (35640)
+ buildings_tools (35669)
+ o5m (35640)
+ pbf (35650)
+ poly (35640)
+ reverter (35640)
+ undelete (35640)
+ utilsplugin2 (35671)

Validator rules:
+ c:\josm\core\resources\data\validator\geometry.mapcss

[GerdP]

The memory leak should be fixed with this small patch:

src/org/openstreetmap/josm/gui/MapView.java

@@ -397 +397 @@
         ProjectionRegistry.removeProjectionChangeListener(layer);
         layer.removePropertyChangeListener(this);
         invalidatedListener.removeFrom(layer);
+        if(layer == getNativeScaleLayer())
+            setNativeScaleLayer(null);
         layer.destroy();
         AudioPlayer.reset();

We changed the behaviour of the zoom keys so often that I am no longer sure what exactly should happen.