ui: Switch to MODE_SCROLLABLE when tab width is about to overflow

...to prevent tabs from inserting line breaks.

app-common/src/main/java/im/angry/openeuicc/ui/widget/DynamicModeTabLayout.kt

@@ -0,0 +1,51 @@
+package im.angry.openeuicc.ui.widget
+
+import android.content.Context
+import android.util.AttributeSet
+import android.view.ViewGroup
+import com.google.android.material.R
+import com.google.android.material.tabs.TabLayout
+
+/**
+ * A TabLayout that automatically switches to MODE_SCROLLABLE when
+ * child tabs overflow the full width of the layout.
+ */
+class DynamicModeTabLayout @JvmOverloads constructor(
+    context: Context,
+    attrs: AttributeSet? = null,
+    defStyleAttr: Int = R.attr.tabStyle
+) : TabLayout(context, attrs, defStyleAttr) {
+    init {
+        addOnLayoutChangeListener { _, _, _, _, _, _, _, _, _ ->
+            updateModeIfNecessary()
+        }
+    }
+
+    private fun updateModeIfNecessary() {
+        if (width <= 0 || tabCount == 0) return
+
+        val tabStrip = getChildAt(0) as? ViewGroup ?: return
+        val totalTabWidth = (0 until tabStrip.childCount).sumOf { index ->
+            val tabView = tabStrip.getChildAt(index)
+            val layoutParams = tabView.layoutParams as? MarginLayoutParams
+            tabView.measure(
+                MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED),
+                MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED)
+            )
+            tabView.measuredWidth + (layoutParams?.leftMargin ?: 0) + (layoutParams?.rightMargin ?: 0)
+        }
+
+        val availableWidth = width - paddingLeft - paddingRight
+        val shouldScroll = totalTabWidth > availableWidth
+        val targetMode = if (shouldScroll) MODE_SCROLLABLE else MODE_FIXED
+        val targetGravity = if (shouldScroll) GRAVITY_START else GRAVITY_FILL
+
+        if (tabMode != targetMode) {
+            tabMode = targetMode
+        }
+
+        if (tabGravity != targetGravity) {
+            tabGravity = targetGravity
+        }
+    }
+}

app-common/src/main/res/layout/activity_main.xml

@@ -6,7 +6,7 @@
 
     <include layout="@layout/toolbar_activity" />
 
-    <com.google.android.material.tabs.TabLayout
+    <im.angry.openeuicc.ui.widget.DynamicModeTabLayout
         android:id="@+id/main_tabs"
         android:layout_width="match_parent"
         android:layout_height="wrap_content"