Fix/dtc module picker scroll

app/src/main/java/org/obd/graphs/preferences/dtc/DiagnosticTroubleCodePreferenceDialogFragment.kt

@@ -243,9 +243,11 @@ internal class DiagnosticTroubleCodePreferenceDialogFragment : CoreDialogFragmen
             }
         )
 
+        // Inflated from XML (rather than constructed in code) so it can carry a custom, always-on
+        // scrollbar thumb on every API level - the theme default is thin and barely visible, and
+        // it's the only hint that more modules sit below the fold.
         val listView =
-            android.widget.ListView(context).apply {
-                choiceMode = android.widget.ListView.CHOICE_MODE_MULTIPLE
+            (LayoutInflater.from(context).inflate(R.layout.dtc_module_list, container, false) as MaxHeightListView).apply {
                 adapter =
                     android.widget.ArrayAdapter(
                         context,
@@ -256,11 +258,15 @@ internal class DiagnosticTroubleCodePreferenceDialogFragment : CoreDialogFragmen
                     setItemChecked(index, true)
                 }
             }
+        // Zero height + weight lets the LinearLayout shrink the list (which scrolls on its own)
+        // when there are more modules than fit on screen - with WRAP_CONTENT it would claim its
+        // full height and push the button bar below out of the dialog.
         container.addView(
             listView,
             android.widget.LinearLayout.LayoutParams(
                 android.widget.LinearLayout.LayoutParams.MATCH_PARENT,
-                android.widget.LinearLayout.LayoutParams.WRAP_CONTENT
+                0,
+                1f
             )
         )
 

app/src/main/java/org/obd/graphs/preferences/dtc/MaxHeightListView.kt

@@ -0,0 +1,50 @@
+/*
+ * Copyright 2019-2026, Tomasz Żebrowski
+ *
+ * <p>Licensed to the Apache Software Foundation (ASF) under one or more contributor license
+ * agreements. See the NOTICE file distributed with this work for additional information regarding
+ * copyright ownership. The ASF licenses this file to You under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the License. You may obtain a
+ * copy of the License at
+ *
+ * <p>http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * <p>Unless required by applicable law or agreed to in writing, software distributed under the
+ * License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
+ * express or implied. See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.obd.graphs.preferences.dtc
+
+import android.content.Context
+import android.util.AttributeSet
+import android.widget.ListView
+
+// A ListView that never grows beyond a fraction of the screen height. Inside the DTC module
+// picker (an AlertDialog custom view) a plain wrap_content/weighted ListView still claimed the
+// whole dialog height when the module list was long, pushing the button bar out of view - an
+// explicit cap keeps room for the buttons regardless of how the dialog window gets measured.
+class MaxHeightListView
+@JvmOverloads
+constructor(
+    context: Context,
+    attrs: AttributeSet? = null,
+    defStyleAttr: Int = android.R.attr.listViewStyle
+) : ListView(context, attrs, defStyleAttr) {
+    var maxHeightRatio: Float = 0.4f
+
+    override fun onMeasure(
+        widthMeasureSpec: Int,
+        heightMeasureSpec: Int
+    ) {
+        val maxHeight = (resources.displayMetrics.heightPixels * maxHeightRatio).toInt()
+        val size = MeasureSpec.getSize(heightMeasureSpec)
+        val cappedSpec =
+            when (MeasureSpec.getMode(heightMeasureSpec)) {
+                MeasureSpec.UNSPECIFIED -> MeasureSpec.makeMeasureSpec(maxHeight, MeasureSpec.AT_MOST)
+                MeasureSpec.EXACTLY -> MeasureSpec.makeMeasureSpec(minOf(size, maxHeight), MeasureSpec.EXACTLY)
+                else -> MeasureSpec.makeMeasureSpec(minOf(size, maxHeight), MeasureSpec.AT_MOST)
+            }
+        super.onMeasure(widthMeasureSpec, cappedSpec)
+    }
+}

app/src/main/res/drawable/dtc_module_list_scrollbar_thumb.xml

@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="utf-8"?>
+<shape xmlns:android="http://schemas.android.com/apk/res/android"
+    android:shape="rectangle">
+    <solid android:color="#9E9E9E" />
+    <corners android:radius="3dp" />
+    <size android:width="6dp" />
+</shape>

app/src/main/res/layout/dialog_dtc.xml

@@ -70,6 +70,7 @@
         <LinearLayout
             android:layout_width="match_parent"
             android:layout_height="wrap_content"
+            android:baselineAligned="false"
             android:orientation="horizontal">
 
             <Button
@@ -98,6 +99,7 @@
             android:layout_width="match_parent"
             android:layout_height="wrap_content"
             android:layout_marginTop="2dp"
+            android:baselineAligned="false"
             android:orientation="horizontal">
 
             <Button

app/src/main/res/layout/dtc_module_list.xml

@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="utf-8"?>
+<org.obd.graphs.preferences.dtc.MaxHeightListView xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:choiceMode="multipleChoice"
+    android:fadeScrollbars="false"
+    android:scrollbarAlwaysDrawVerticalTrack="true"
+    android:scrollbarSize="6dp"
+    android:scrollbarStyle="insideOverlay"
+    android:scrollbarThumbVertical="@drawable/dtc_module_list_scrollbar_thumb"
+    android:scrollbars="vertical" />