feat: Add RAM usage overlay and improve thermal display

- Add new RAM usage overlay showing current/max memory usage with color gradient
- Simplify thermal overlay to show temperature in C/F with color indication
- Add SHOW_RAM_OVERLAY boolean setting (disabled by default in UI)
- Set default values for thermal overlay and black backgrounds to true
- Update copyright headers to include Citron Emulator Project

The RAM overlay displays native heap usage with color gradient from green
(low usage) to red (high usage). The thermal display was simplified to show
just temperatures while maintaining the color indication based on system
thermal status.

src/android/app/src/main/java/org/citron/citron_emu/features/settings/model/BooleanSetting.kt

@@ -1,4 +1,5 @@
 // SPDX-FileCopyrightText: 2023 yuzu Emulator Project
+// SPDX-FileCopyrightText: 2025 Citron Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
 package org.citron.citron_emu.features.settings.model
@@ -27,6 +28,7 @@ enum class BooleanSetting(override val key: String) : AbstractBooleanSetting {
     SHOW_INPUT_OVERLAY("show_input_overlay"),
     TOUCHSCREEN("touchscreen"),
     SHOW_THERMAL_OVERLAY("show_thermal_overlay"),
+    SHOW_RAM_OVERLAY("show_ram_overlay"),
     USE_AUTO_STUB("use_auto_stub");
 
     override fun getBoolean(needsGlobal: Boolean): Boolean =

src/android/app/src/main/java/org/citron/citron_emu/fragments/EmulationFragment.kt

@@ -1,4 +1,5 @@
 // SPDX-FileCopyrightText: 2023 yuzu Emulator Project
+// SPDX-FileCopyrightText: 2025 Citron Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
 package org.citron.citron_emu.fragments
@@ -11,9 +12,11 @@ import android.content.Intent
 import android.content.IntentFilter
 import android.content.pm.ActivityInfo
 import android.content.res.Configuration
+import android.graphics.Color
 import android.net.Uri
 import android.os.BatteryManager
 import android.os.Bundle
+import android.os.Debug
 import android.os.Handler
 import android.os.Looper
 import android.os.PowerManager
@@ -68,6 +71,7 @@ class EmulationFragment : Fragment(), SurfaceHolder.Callback {
     private var emulationActivity: EmulationActivity? = null
     private var perfStatsUpdater: (() -> Unit)? = null
     private var thermalStatsUpdater: (() -> Unit)? = null
+    private var ramStatsUpdater: (() -> Unit)? = null
 
     private var _binding: FragmentEmulationBinding? = null
     private val binding get() = _binding!!
@@ -83,6 +87,8 @@ class EmulationFragment : Fragment(), SurfaceHolder.Callback {
 
     private lateinit var powerManager: PowerManager
 
+    private val ramStatsUpdateHandler = Handler(Looper.myLooper()!!)
+
     override fun onAttach(context: Context) {
         super.onAttach(context)
         if (context is EmulationActivity) {
@@ -376,6 +382,7 @@ class EmulationFragment : Fragment(), SurfaceHolder.Callback {
                 // Setup overlays
                 updateShowFpsOverlay()
                 updateThermalOverlay()
+                updateRamOverlay()
             }
         }
         emulationViewModel.isEmulationStopping.collect(viewLifecycleOwner) {
@@ -470,6 +477,9 @@ class EmulationFragment : Fragment(), SurfaceHolder.Callback {
 
     override fun onDestroyView() {
         super.onDestroyView()
+        if (ramStatsUpdater != null) {
+            ramStatsUpdateHandler.removeCallbacks(ramStatsUpdater!!)
+        }
         _binding = null
     }
 
@@ -552,8 +562,9 @@ class EmulationFragment : Fragment(), SurfaceHolder.Callback {
             emulationViewModel.emulationStarted.value &&
             !emulationViewModel.isEmulationStopping.value
         ) {
-            // Get thermal status
+            // Get thermal status for color
             val thermalStatus = when (powerManager.currentThermalStatus) {
+                PowerManager.THERMAL_STATUS_NONE -> 0f
                 PowerManager.THERMAL_STATUS_LIGHT -> 0.25f
                 PowerManager.THERMAL_STATUS_MODERATE -> 0.5f
                 PowerManager.THERMAL_STATUS_SEVERE -> 0.75f
@@ -563,34 +574,57 @@ class EmulationFragment : Fragment(), SurfaceHolder.Callback {
                 else -> 0f
             }
 
-            // Convert to Fahrenheit for additional info
+            // Convert to Fahrenheit
             val fahrenheit = (temperature * 9f / 5f) + 32f
 
-            // Create progress bar using block elements
+            // Color based on thermal status (green to red)
-            val progressBarLength = 12
+            val red = (thermalStatus * 255).toInt()
-            val filledBars = (thermalStatus * progressBarLength).toInt()
+            val green = ((1f - thermalStatus) * 255).toInt()
-            val progressBar = buildString {
-                append("│") // Left border
-                repeat(filledBars) { append("█") }
-                repeat(progressBarLength - filledBars) { append("░") }
-                append("│") // Right border
-                append(" ")
-                append(String.format("%3d%%", (thermalStatus * 100).toInt()))
-            }
-
-            // Color interpolation based on temperature (green at 30°C, red at 45°C)
-            val normalizedTemp = ((temperature - 30f) / 15f).coerceIn(0f, 1f)
-            val red = (normalizedTemp * 255).toInt()
-            val green = ((1f - normalizedTemp) * 255).toInt()
             val color = android.graphics.Color.rgb(red, green, 0)
 
             binding.showThermalsText.setTextColor(color)
-            binding.showThermalsText.text = String.format(
+            binding.showThermalsText.text = String.format("%.1f°C • %.1f°F", temperature, fahrenheit)
-                "%s\n%.1f°C • %.1f°F",
+        }
-                progressBar,
+    }
-                temperature,
+
-                fahrenheit
+    private fun updateRamOverlay() {
+        val showOverlay = BooleanSetting.SHOW_RAM_OVERLAY.getBoolean()
+        binding.showRamText.setVisible(showOverlay)
+        if (showOverlay) {
+            ramStatsUpdater = {
+                if (emulationViewModel.emulationStarted.value &&
+                    !emulationViewModel.isEmulationStopping.value
+                ) {
+                    val runtime = Runtime.getRuntime()
+                    val nativeHeapSize = Debug.getNativeHeapSize()
+                    val nativeHeapFreeSize = Debug.getNativeHeapFreeSize()
+                    val nativeHeapUsed = nativeHeapSize - nativeHeapFreeSize
+
+                    val usedMemInMB = nativeHeapUsed / 1048576L
+                    val maxMemInMB = nativeHeapSize / 1048576L
+                    val percentUsed = (nativeHeapUsed.toFloat() / nativeHeapSize.toFloat() * 100f)
+
+                    // Color interpolation from green to red based on usage percentage
+                    val normalizedUsage = (percentUsed / 100f).coerceIn(0f, 1f)
+                    val red = (normalizedUsage * 255).toInt()
+                    val green = ((1f - normalizedUsage) * 255).toInt()
+                    val color = Color.rgb(red, green, 0)
+
+                    binding.showRamText.setTextColor(color)
+                    binding.showRamText.text = String.format(
+                        "\nRAM: %d/%d MB (%.1f%%)",
+                        usedMemInMB,
+                        maxMemInMB,
+                        percentUsed
                     )
+                    ramStatsUpdateHandler.postDelayed(ramStatsUpdater!!, 1000)
+                }
+            }
+            ramStatsUpdateHandler.post(ramStatsUpdater!!)
+        } else {
+            if (ramStatsUpdater != null) {
+                ramStatsUpdateHandler.removeCallbacks(ramStatsUpdater!!)
+            }
         }
     }
 
@@ -723,6 +757,10 @@ class EmulationFragment : Fragment(), SurfaceHolder.Callback {
                 BooleanSetting.SHOW_PERFORMANCE_OVERLAY.getBoolean()
             findItem(R.id.thermal_indicator).isChecked =
                 BooleanSetting.SHOW_THERMAL_OVERLAY.getBoolean()
+            findItem(R.id.ram_meter).apply {
+                isChecked = BooleanSetting.SHOW_RAM_OVERLAY.getBoolean()
+                isEnabled = false  // This grays out the option
+            }
             findItem(R.id.menu_rel_stick_center).isChecked =
                 BooleanSetting.JOYSTICK_REL_CENTER.getBoolean()
             findItem(R.id.menu_dpad_slide).isChecked = BooleanSetting.DPAD_SLIDE.getBoolean()
@@ -749,6 +787,11 @@ class EmulationFragment : Fragment(), SurfaceHolder.Callback {
                     true
                 }
 
+                R.id.ram_meter -> {
+                    // Do nothing since it's disabled
+                    true
+                }
+
                 R.id.menu_edit_overlay -> {
                     binding.drawerLayout.close()
                     binding.surfaceInputOverlay.requestFocus()

src/android/app/src/main/jni/android_settings.h

@@ -1,4 +1,5 @@
 // SPDX-FileCopyrightText: 2023 yuzu Emulator Project
+// SPDX-FileCopyrightText: 2025 Citron Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
 #pragma once
@@ -51,7 +52,7 @@ struct Values {
 
     Settings::Setting<s32> theme{linkage, 0, "theme", Settings::Category::Android};
     Settings::Setting<s32> theme_mode{linkage, -1, "theme_mode", Settings::Category::Android};
-    Settings::Setting<bool> black_backgrounds{linkage, false, "black_backgrounds",
+    Settings::Setting<bool> black_backgrounds{linkage, true, "black_backgrounds",
                                               Settings::Category::Android};
 
     // Input/performance overlay settings
@@ -67,7 +68,9 @@ struct Values {
                                             Settings::Category::Overlay};
     Settings::Setting<bool> show_performance_overlay{linkage, true, "show_performance_overlay",
                                                      Settings::Category::Overlay};
-    Settings::Setting<bool> show_thermal_overlay{linkage, false, "show_thermal_overlay",
+    Settings::Setting<bool> show_thermal_overlay{linkage, true, "show_thermal_overlay",
+                                                 Settings::Category::Overlay};
+    Settings::Setting<bool> show_ram_overlay{linkage, true, "show_ram_overlay",
                                              Settings::Category::Overlay};
     Settings::Setting<bool> show_input_overlay{linkage, true, "show_input_overlay",
                                                Settings::Category::Overlay};

src/android/app/src/main/res/layout/fragment_emulation.xml

@@ -171,6 +171,21 @@
 
         </FrameLayout>
 
+        <com.google.android.material.textview.MaterialTextView
+            android:id="@+id/show_ram_text"
+            style="@style/TextAppearance.Material3.BodySmall"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:layout_gravity="left"
+            android:layout_marginTop="24dp"
+            android:clickable="false"
+            android:focusable="false"
+            android:textColor="@android:color/white"
+            android:shadowColor="@android:color/black"
+            android:shadowRadius="3"
+            android:layout_below="@id/show_fps_text"
+            tools:ignore="RtlHardcoded" />
+
     </androidx.coordinatorlayout.widget.CoordinatorLayout>
 
     <com.google.android.material.navigation.NavigationView

src/android/app/src/main/res/menu/menu_overlay_options.xml

@@ -11,6 +11,11 @@
         android:title="@string/emulation_thermal_indicator"
         android:checkable="true" />
 
+    <item
+        android:id="@+id/ram_meter"
+        android:title="@string/emulation_ram_meter"
+        android:checkable="true" />
+
     <item
         android:id="@+id/menu_edit_overlay"
         android:title="@string/emulation_touch_overlay_edit" />

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

@@ -480,6 +480,7 @@
     <string name="emulation_done">Done</string>
     <string name="emulation_fps_counter">FPS counter</string>
     <string name="emulation_thermal_indicator">Thermal indicator</string>
+    <string name="emulation_ram_meter">RAM meter</string>
     <string name="emulation_toggle_controls">Toggle controls</string>
     <string name="emulation_rel_stick_center">Relative stick center</string>
     <string name="emulation_dpad_slide">D-pad slide</string>