replace the qr display density toggle with low, medium and high levels that produce the same qr code version for ur and bbqr

### src/main/java/com/sparrowwallet/sparrow/control/QRDensity.java
@@ -1,8 +1,13 @@
 package com.sparrowwallet.sparrow.control;
 
+/**
+ * QR code density levels applying to all encodings. For each level, the UR and BBQr fragment lengths are chosen to produce the same maximum QR code version
+ * (7, 17 and 27 respectively), since scanner capability does not depend on the encoding.
+ */
 public enum QRDensity {
-    NORMAL("Normal", 400, 2000),
-    LOW("Low", 80, 1000);
+    LOW("Low", 80, 216),
+    NORMAL("Medium", 400, 928),
+    HIGH("High", 1000, 2000);
 
     private final String name;
     private final int maxUrFragmentLength;
@@ -25,4 +30,9 @@ public int getMaxUrFragmentLength() {
     public int getMaxBbqrFragmentLength() {
         return maxBbqrFragmentLength;
     }
+
+    @Override
+    public String toString() {
+        return name + " Density";
+    }
 }

### src/main/java/com/sparrowwallet/sparrow/control/QRDisplayDialog.java
@@ -10,7 +10,6 @@
 import com.sparrowwallet.hummingbird.registry.RegistryType;
 import com.sparrowwallet.sparrow.AppServices;
 import com.sparrowwallet.sparrow.glyphfont.FontAwesome5;
-import com.sparrowwallet.sparrow.glyphfont.GlyphUtils;
 import com.sparrowwallet.sparrow.io.Config;
 import com.sparrowwallet.sparrow.io.ImportException;
 import com.sparrowwallet.hummingbird.UR;
@@ -63,6 +62,8 @@ public class QRDisplayDialog extends Dialog<ButtonType> {
 
     private QREncoding encoding = QREncoding.UR;
 
+    private QRDensity defaultDensity;
+
     private final ImageView qrImageView;
 
     private AnimateQRService animateQRService;
@@ -92,13 +93,22 @@ public QRDisplayDialog(UR ur, BBQR bbqr, String raw, boolean addLegacyEncodingOp
         this.bbqr = bbqr;
         this.addLegacyEncodingOption = bbqr == null && addLegacyEncodingOption;
 
-        this.urEncoder = new UREncoder(ur, Config.get().getQrDensity().getMaxUrFragmentLength(), MIN_FRAGMENT_LENGTH, 0);
+        if(bbqr != null && (defaultEncoding == QREncoding.BBQR || Config.get().getQrEncoding() == QREncoding.BBQR)) {
+            encoding = QREncoding.BBQR;
+        }
+
+        //Until a density level is chosen, use the level closest to the previous density setting, which applied to each encoding separately
+        QRDensity legacyDensity = Config.get().getLegacyQrDensity();
+        if(encoding == QREncoding.BBQR) {
+            this.defaultDensity = legacyDensity == QRDensity.LOW ? QRDensity.NORMAL : QRDensity.HIGH;
+        } else {
+            this.defaultDensity = legacyDensity == QRDensity.LOW ? QRDensity.LOW : QRDensity.NORMAL;
+        }
+
+        this.urEncoder = new UREncoder(ur, getQRDensity().getMaxUrFragmentLength(), MIN_FRAGMENT_LENGTH, 0);
 
         if(bbqr != null) {
-            this.bbqrEncoder = new BBQREncoder(bbqr.type(), DEFAULT_BBQR_ENCODING, bbqr.data(), Config.get().getQrDensity().getMaxBbqrFragmentLength(), 0);
-            if(defaultEncoding == QREncoding.BBQR || Config.get().getQrEncoding() == QREncoding.BBQR) {
-                encoding = QREncoding.BBQR;
-            }
+            this.bbqrEncoder = new BBQREncoder(bbqr.type(), DEFAULT_BBQR_ENCODING, bbqr.data(), getQRDensity().getMaxBbqrFragmentLength(), 0);
         }
 
         this.raw = raw;
@@ -302,16 +312,20 @@ private void setEncoding(QREncoding encoding) {
         restartAnimation();
     }
 
+    private QRDensity getQRDensity() {
+        return Config.get().getQrDensity() == null ? defaultDensity : Config.get().getQrDensity();
+    }
+
     private void changeQRDensity() {
         if(animateQRService != null) {
             animateQRService.cancel();
         }
 
         if(bbqr != null) {
-            this.bbqrEncoder = new BBQREncoder(bbqr.type(), DEFAULT_BBQR_ENCODING, bbqr.data(), Config.get().getQrDensity().getMaxBbqrFragmentLength(), 0);
+            this.bbqrEncoder = new BBQREncoder(bbqr.type(), DEFAULT_BBQR_ENCODING, bbqr.data(), getQRDensity().getMaxBbqrFragmentLength(), 0);
         }
 
-        this.urEncoder = new UREncoder(ur, Config.get().getQrDensity().getMaxUrFragmentLength(), MIN_FRAGMENT_LENGTH, 0);
+        this.urEncoder = new UREncoder(ur, getQRDensity().getMaxUrFragmentLength(), MIN_FRAGMENT_LENGTH, 0);
 
         restartAnimation();
     }
@@ -365,29 +379,32 @@ protected Node createButton(ButtonType buttonType) {
 
                     return legacy;
                 } else {
-                    Button density = new Button(buttonType.getText());
-                    density.setPrefWidth(160);
-                    density.setGraphicTextGap(5);
-                    updateDensityButton(density);
+                    ComboBox<QRDensity> densityComboBox = new ComboBox<>();
+                    densityComboBox.getItems().addAll(QRDensity.values());
+                    densityComboBox.setValue(getQRDensity());
 
                     final ButtonBar.ButtonData buttonData = buttonType.getButtonData();
-                    ButtonBar.setButtonData(density, buttonData);
-                    density.setOnAction(event -> {
+                    ButtonBar.setButtonData(densityComboBox, buttonData);
+                    densityComboBox.setOnAction(_ -> {
+                        if(densityComboBox.getValue() == getQRDensity()) {
+                            return;
+                        }
+
                         if(!initialDensityChange && !isSinglePart()) {
                             Optional<ButtonType> optButtonType = AppServices.showWarningDialog("Discard progress?", "Changing the QR code density means any progress on the receiving device must be discarded. Proceed?", ButtonType.NO, ButtonType.YES);
                             if(optButtonType.isPresent() && optButtonType.get() == ButtonType.YES) {
                                 initialDensityChange = true;
                             } else {
+                                densityComboBox.setValue(getQRDensity());
                                 return;
                             }
                         }
 
-                        Config.get().setQrDensity(Config.get().getQrDensity() == QRDensity.NORMAL ? QRDensity.LOW : QRDensity.NORMAL);
-                        updateDensityButton(density);
+                        Config.get().setQrDensity(densityComboBox.getValue());
                         changeQRDensity();
                     });
 
-                    return density;
+                    return densityComboBox;
                 }
             } else if(buttonType.getButtonData() == ButtonBar.ButtonData.OK_DONE) {
                 Button scanButton = (Button)super.createButton(buttonType);
@@ -431,15 +448,6 @@ private void setLegacyGraphic(ToggleButton legacy, boolean useLegacyEncoding) {
                 legacy.setGraphic(getGlyph(FontAwesome5.Glyph.BAN));
             }
         }
-
-        private void updateDensityButton(Button density) {
-            density.setText(Config.get().getQrDensity() == QRDensity.NORMAL ? "Less Dense" : "More Dense");
-            if(Config.get().getQrDensity() == QRDensity.NORMAL) {
-                density.setGraphic(getGlyph(FontAwesome5.Glyph.MAGNIFYING_GLASS_PLUS));
-            } else {
-                density.setGraphic(getGlyph(FontAwesome5.Glyph.MAGNIFYING_GLASS_MINUS));
-            }
-        }
     }
 
     protected static Glyph getGlyph(FontAwesome5.Glyph glyphName) {

### src/main/java/com/sparrowwallet/sparrow/io/Config.java
@@ -68,6 +68,7 @@ public class Config {
     private long dustAttackThresholdSp = DUST_ATTACK_THRESHOLD_SP_SATS;
     private int enumerateHwPeriod = ENUMERATE_HW_PERIOD_SECS;
     private QRDensity qrDensity;
+    private QRDensity qrDensityLevel;
     private QREncoding qrEncoding;
     private WebcamResolution webcamResolution;
     private boolean mirrorCapture = true;
@@ -467,12 +468,16 @@ public int getEnumerateHwPeriod() {
         return enumerateHwPeriod;
     }
 
+    public QRDensity getLegacyQrDensity() {
+        return qrDensity;
+    }
+
     public QRDensity getQrDensity() {
-        return qrDensity == null ? QRDensity.NORMAL : qrDensity;
+        return qrDensityLevel;
     }
 
     public void setQrDensity(QRDensity qrDensity) {
-        this.qrDensity = qrDensity;
+        this.qrDensityLevel = qrDensity;
         flush();
     }
 

### src/test/java/com/sparrowwallet/sparrow/control/QRDensityTest.java
@@ -0,0 +1,45 @@
+package com.sparrowwallet.sparrow.control;
+
+import com.google.zxing.qrcode.decoder.ErrorCorrectionLevel;
+import com.google.zxing.qrcode.encoder.Encoder;
+import com.sparrowwallet.hummingbird.UR;
+import com.sparrowwallet.hummingbird.UREncoder;
+import com.sparrowwallet.sparrow.io.bbqr.BBQREncoder;
+import com.sparrowwallet.sparrow.io.bbqr.BBQREncoding;
+import com.sparrowwallet.sparrow.io.bbqr.BBQRType;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+import java.util.Locale;
+import java.util.Map;
+import java.util.Random;
+
+public class QRDensityTest {
+    private static final Map<QRDensity, Integer> QR_VERSIONS = Map.of(QRDensity.LOW, 7, QRDensity.NORMAL, 17, QRDensity.HIGH, 27);
+
+    @Test
+    public void testEncodingsShareQrVersion() throws Exception {
+        Random random = new Random(1);
+        for(QRDensity density : QRDensity.values()) {
+            int maxUrVersion = 0;
+            int maxBbqrVersion = 0;
+            for(int size = 50; size < 12000; size += 37) {
+                byte[] data = new byte[size];
+                random.nextBytes(data);
+
+                UREncoder urEncoder = new UREncoder(UR.fromBytes("crypto-psbt", data), density.getMaxUrFragmentLength(), 10, 0);
+                maxUrVersion = Math.max(maxUrVersion, getQrVersion(urEncoder.nextPart().toUpperCase(Locale.ROOT)));
+
+                BBQREncoder bbqrEncoder = new BBQREncoder(BBQRType.PSBT, BBQREncoding.ZLIB, data, density.getMaxBbqrFragmentLength(), 0);
+                maxBbqrVersion = Math.max(maxBbqrVersion, getQrVersion(bbqrEncoder.nextPart().toUpperCase(Locale.ROOT)));
+            }
+
+            Assertions.assertEquals(QR_VERSIONS.get(density), maxUrVersion, density + " UR");
+            Assertions.assertEquals(QR_VERSIONS.get(density), maxBbqrVersion, density + " BBQr");
+        }
+    }
+
+    private static int getQrVersion(String part) throws Exception {
+        return Encoder.encode(part, ErrorCorrectionLevel.L).getVersion().getVersionNumber();
+    }
+}