Implement fixed aspect ratio surface

Adds a setting to letterbox the surface with black bars to 16:9 or 21:9 aspect ratio to avoid stretching out the rendered image

app/src/main/java/emu/skyline/EmulationActivity.kt

@@ -12,6 +12,7 @@ import android.content.res.AssetManager
 import android.graphics.PointF
 import android.os.*
 import android.util.Log
+import android.util.Rational
 import android.view.*
 import androidx.appcompat.app.AppCompatActivity
 import androidx.core.view.isGone
@@ -221,9 +222,6 @@ class EmulationActivity : AppCompatActivity(), SurfaceHolder.Callback, View.OnTo
         returnFromEmulation()
     }
 
-    /**
-     * This makes the window fullscreen, sets up the performance statistics and finally calls [executeApplication] for executing the application
-     */
     @SuppressLint("SetTextI18n", "ClickableViewAccessibility")
     override fun onCreate(savedInstanceState : Bundle?) {
         super.onCreate(savedInstanceState)
@@ -237,6 +235,14 @@ class EmulationActivity : AppCompatActivity(), SurfaceHolder.Callback, View.OnTo
 
         binding.gameView.holder.addCallback(this)
 
+        binding.gameView.setAspectRatio(
+            when (settings.aspectRatio) {
+                0 -> Rational(16, 9)
+                1 -> Rational(21, 9)
+                else -> null
+            }
+        )
+
         if (settings.perfStats) {
             binding.perfStats.apply {
                 postDelayed(object : Runnable {

app/src/main/java/emu/skyline/utils/Settings.kt

@@ -38,5 +38,7 @@ class Settings @Inject constructor(@ApplicationContext private val context : Con
 
     var maxRefreshRate by sharedPreferences(context, false)
 
+    var aspectRatio by sharedPreferences(context, 0)
+
     var systemLanguage by sharedPreferences(context, 1)
 }

app/src/main/java/emu/skyline/views/FixedRatioSurfaceView.kt

@@ -0,0 +1,39 @@
+package emu.skyline.views
+
+import android.content.Context
+import android.util.AttributeSet
+import android.util.Rational
+import android.view.SurfaceView
+import kotlin.math.roundToInt
+
+class FixedRatioSurfaceView @JvmOverloads constructor(context : Context, attrs : AttributeSet? = null, defStyleAttr : Int = 0) : SurfaceView(context, attrs, defStyleAttr) {
+    private var aspectRatio : Float = 0f // (width / height), 0f is a special value for stretch
+
+    /**
+     * Sets the desired aspect ratio for this view
+     * @param ratio the ratio to force the view to, or null to stretch to fit
+     */
+    fun setAspectRatio(ratio : Rational?) {
+        aspectRatio = ratio?.toFloat() ?: 0f
+    }
+
+    override fun onMeasure(widthMeasureSpec : Int, heightMeasureSpec : Int) {
+        super.onMeasure(widthMeasureSpec, heightMeasureSpec)
+        val width = MeasureSpec.getSize(widthMeasureSpec)
+        val height = MeasureSpec.getSize(heightMeasureSpec)
+        if (aspectRatio != 0f) {
+            val newWidth : Int
+            val newHeight : Int
+            if (height * aspectRatio < width) {
+                newWidth = (height * aspectRatio).roundToInt()
+                newHeight = height
+            } else {
+                newWidth = width
+                newHeight = (width / aspectRatio).roundToInt()
+            }
+            setMeasuredDimension(newWidth, newHeight)
+        } else {
+            setMeasuredDimension(width, height)
+        }
+    }
+}

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

@@ -5,14 +5,14 @@
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     android:keepScreenOn="true"
-        tools:background="@android:color/black"
+    android:background="@android:color/black"
     tools:context=".EmulationActivity">
 
-    <SurfaceView
+    <emu.skyline.views.FixedRatioSurfaceView
         android:id="@+id/game_view"
         android:layout_width="match_parent"
         android:layout_height="match_parent"
-            tools:visibility="invisible" />
+        android:layout_gravity="center" />
 
     <emu.skyline.input.onscreen.OnScreenControllerView
         android:id="@+id/on_screen_controller_view"

app/src/main/res/values/array.xml

@@ -74,4 +74,9 @@
         <item>7</item>
         <item>11</item>
     </integer-array>
+    <string-array name="aspect_ratios">
+        <item>16:9 (Switch, Recommended)</item>
+        <item>21:9 (Ultrawide Mods)</item>
+        <item>Device Aspect Ratio (Stretch to fit)</item>
+    </string-array>
 </resources>

app/src/main/res/values/strings.xml

@@ -61,6 +61,7 @@
     <string name="max_refresh_rate">Use Maximum Display Refresh Rate</string>
     <string name="max_refresh_rate_enabled">Sets the display refresh rate as high as possible (Will break most games)</string>
     <string name="max_refresh_rate_disabled">Sets the display refresh rate to 60Hz</string>
+    <string name="aspect_ratio">Aspect Ratio</string>
     <!-- Input -->
     <string name="input">Input</string>
     <string name="osc">On-Screen Controls</string>

app/src/main/res/xml/preferences.xml

@@ -103,6 +103,12 @@
             android:summaryOn="@string/max_refresh_rate_enabled"
             app:key="max_refresh_rate"
             app:title="@string/max_refresh_rate" />
+        <emu.skyline.preference.IntegerListPreference
+            android:defaultValue="0"
+            android:entries="@array/aspect_ratios"
+            app:key="aspect_ratio"
+            app:title="@string/aspect_ratio"
+            app:useSimpleSummaryProvider="true" />
     </PreferenceCategory>
     <PreferenceCategory
         android:key="category_input"