diff --git a/generator/build.gradle b/generator/build.gradle
index aa7403f..190d42b 100644
--- a/generator/build.gradle
+++ b/generator/build.gradle
@@ -5,7 +5,7 @@ buildscript {
 }
     
 plugins {
-    id 'org.sonarqube' version '3.3'
+    id 'org.sonarqube' version '4.2.1.3168'
     id 'java-library'
     id 'maven-publish'
     id 'signing'
@@ -41,10 +41,8 @@ jar {
 test {
     useJUnitPlatform()
     finalizedBy jacocoTestReport
-    reports {
-        junitXml.required = false
-        html.required = true
-    }               
+    reports.junitXml.required = false
+    reports.html.required = true
 }
 
 javadoc {
@@ -111,7 +109,7 @@ signing {
     sign publishing.publications.mavenJava
 }
 
-sonarqube {
+sonar {
     properties {
         property 'sonar.projectName', 'Swiss QR Bill Generator (Java)'
     }
@@ -119,11 +117,9 @@ sonarqube {
 
 jacocoTestReport {
     dependsOn test
-    reports {
-        xml.required = true
-        csv.required = false
-        html.required = false
-    }
+    reports.xml.required = true
+    reports.csv.required = false
+    reports.html.required = false
 }
 
 project.tasks["sonarqube"].dependsOn "jacocoTestReport"
@@ -133,9 +129,9 @@ tasks.withType(JavaCompile) {
 }
 
 dependencies {
-    api 'org.apache.pdfbox:pdfbox:2.0.26'
+    api 'org.apache.pdfbox:pdfbox:2.0.29'
     implementation 'io.nayuki:qrcodegen:1.8.0'
-    testImplementation 'org.junit.jupiter:junit-jupiter-api:5.9.1'
-    testImplementation 'org.junit.jupiter:junit-jupiter-params:5.9.1'
-    testRuntimeOnly 'org.junit.jupiter:junit-jupiter-engine:5.9.1'
+    testImplementation 'org.junit.jupiter:junit-jupiter-api:5.9.3'
+    testImplementation 'org.junit.jupiter:junit-jupiter-params:5.9.3'
+    testRuntimeOnly 'org.junit.jupiter:junit-jupiter-engine:5.9.3'
 }
diff --git a/generator/src/main/java/net/codecrete/qrbill/canvas/AbstractCanvas.java b/generator/src/main/java/net/codecrete/qrbill/canvas/AbstractCanvas.java
index eef43b1..21c6c4c 100644
--- a/generator/src/main/java/net/codecrete/qrbill/canvas/AbstractCanvas.java
+++ b/generator/src/main/java/net/codecrete/qrbill/canvas/AbstractCanvas.java
@@ -21,6 +21,12 @@ public abstract class AbstractCanvas implements Canvas {
      */
     protected static final double MM_TO_PT = 72 / 25.4;
 
+    /**
+     * Font metrics information.
+     * <p>
+     * Available once {@link #setupFontMetrics(String)} has been called.
+     * </p>
+     */
     protected FontMetrics fontMetrics;
 
     /**