From 92ae7de2892bb9d7eadfe6c860ab03351b2f13ed Mon Sep 17 00:00:00 2001
From: Romain Vimont <rom@rom1v.com>
Date: Wed, 15 Apr 2026 19:40:17 +0200
Subject: [PATCH] Extract display properties tracker

`DisplayMonitor` listens for system display events. Move the
event-handling logic into a separate class (`DisplayPropertiesTracker`),
as it will become more complex in the following commit.
---
 .../scrcpy/display/DisplayMonitor.java        | 54 ++++++-------------
 .../display/DisplayPropertiesTracker.java     | 43 +++++++++++++++
 2 files changed, 59 insertions(+), 38 deletions(-)
 create mode 100644 server/src/main/java/com/genymobile/scrcpy/display/DisplayPropertiesTracker.java

diff --git a/server/src/main/java/com/genymobile/scrcpy/display/DisplayMonitor.java b/server/src/main/java/com/genymobile/scrcpy/display/DisplayMonitor.java
index 5a31fff5..31ff97d9 100644
--- a/server/src/main/java/com/genymobile/scrcpy/display/DisplayMonitor.java
+++ b/server/src/main/java/com/genymobile/scrcpy/display/DisplayMonitor.java
@@ -25,6 +25,8 @@ public class DisplayMonitor {
     // So use the default method only before Android 14.
     private static final boolean USE_DEFAULT_METHOD = Build.VERSION.SDK_INT < AndroidVersions.API_34_ANDROID_14;
 
+    private final DisplayPropertiesTracker tracker = new DisplayPropertiesTracker();
+
     private DisplayManager.DisplayListenerHandle displayListenerHandle;
     private HandlerThread handlerThread;
 
@@ -32,8 +34,6 @@ public class DisplayMonitor {
 
     private int displayId = Device.DISPLAY_ID_NONE;
 
-    private DisplayProperties props;
-
     private Listener listener;
 
     public void start(int displayId, Listener listener) {
@@ -48,15 +48,16 @@ public class DisplayMonitor {
             handlerThread = new HandlerThread("DisplayListener");
             handlerThread.start();
             Handler handler = new Handler(handlerThread.getLooper());
-            displayListenerHandle = ServiceManager.getDisplayManager().registerDisplayListener(eventDisplayId -> {
-                if (Ln.isEnabled(Ln.Level.VERBOSE)) {
-                    Ln.v("DisplayMonitor: onDisplayChanged(" + eventDisplayId + ")");
-                }
+            displayListenerHandle = ServiceManager.getDisplayManager().registerDisplayListener(
+                    eventDisplayId -> {
+                        if (Ln.isEnabled(Ln.Level.VERBOSE)) {
+                            Ln.v("DisplayMonitor: onDisplayChanged(" + eventDisplayId + ")");
+                        }
 
-                if (eventDisplayId == displayId) {
-                    checkDisplayPropertiesChanged();
-                }
-            }, handler);
+                        if (eventDisplayId == displayId) {
+                            checkDisplayPropertiesChanged();
+                        }
+                    }, handler);
         } else {
             displayWindowListener = new DisplayWindowListener() {
                 @Override
@@ -96,39 +97,16 @@ public class DisplayMonitor {
         }
     }
 
-    private synchronized DisplayProperties getAndSetDisplayProperties(DisplayProperties props) {
-        DisplayProperties oldProps = this.props;
-        this.props = props;
-        return oldProps;
-    }
-
-    public synchronized void setSessionDisplayProperties(DisplayProperties props) {
-        this.props = props;
+    public void setSessionDisplayProperties(DisplayProperties props) {
+        tracker.setCurrent(props);
     }
 
     private void checkDisplayPropertiesChanged() {
         DisplayInfo di = ServiceManager.getDisplayManager().getDisplayInfo(displayId);
-        if (di == null) {
-            Ln.w("DisplayInfo for " + displayId + " cannot be retrieved");
-            // We can't compare with the current properties, so reset unconditionally
-            DisplayProperties oldProps = getAndSetDisplayProperties(null); // exchange with synchronization
-            if (Ln.isEnabled(Ln.Level.VERBOSE)) {
-                Ln.v("DisplayMonitor: requestReset(): " + oldProps + " -> (unknown)");
-            }
+        DisplayProperties props = di != null ? new DisplayProperties(di.getSize(), di.getRotation()) : null;
+        boolean trigger = tracker.onDisplayPropertiesChanged(props);
+        if (trigger) {
             listener.onDisplayPropertiesChanged();
-        } else {
-            DisplayProperties newProps = new DisplayProperties(di.getSize(), di.getRotation());
-
-            DisplayProperties oldProps = getAndSetDisplayProperties(newProps); // exchange with synchronization
-            if (!newProps.equals(oldProps)) {
-                // Reset only if the properties are different
-                if (Ln.isEnabled(Ln.Level.VERBOSE)) {
-                    Ln.v("DisplayMonitor: requestReset(): " + oldProps + " -> " + newProps);
-                }
-                listener.onDisplayPropertiesChanged();
-            } else if (Ln.isEnabled(Ln.Level.VERBOSE)) {
-                Ln.v("DisplayMonitor: DisplayProperties not changed (" + newProps + "): do not requestReset()");
-            }
         }
     }
 }
diff --git a/server/src/main/java/com/genymobile/scrcpy/display/DisplayPropertiesTracker.java b/server/src/main/java/com/genymobile/scrcpy/display/DisplayPropertiesTracker.java
new file mode 100644
index 00000000..c7d782a2
--- /dev/null
+++ b/server/src/main/java/com/genymobile/scrcpy/display/DisplayPropertiesTracker.java
@@ -0,0 +1,43 @@
+package com.genymobile.scrcpy.display;
+
+import com.genymobile.scrcpy.util.Ln;
+
+public final class DisplayPropertiesTracker {
+    private DisplayProperties props;
+
+    public synchronized void setCurrent(DisplayProperties props) {
+        this.props = props;
+    }
+
+    /**
+     * Set the current display properties, and indicate whether the capture must be reset.
+     *
+     * @param props the current display properties
+     * @return {@code true} if the capture must be reset
+     */
+    public synchronized boolean onDisplayPropertiesChanged(DisplayProperties props) {
+        DisplayProperties prev = this.props;
+        this.props = props;
+
+        if (props == null) {
+            // The display properties have changed, but are unknown, a resize event must be triggered
+            if (Ln.isEnabled(Ln.Level.VERBOSE)) {
+                Ln.v(getClass().getSimpleName() + ": " + prev + " -> (unknown)");
+            }
+            return true;
+        }
+
+        if (props.equals(prev)) {
+            if (Ln.isEnabled(Ln.Level.VERBOSE)) {
+                Ln.v(getClass().getSimpleName() + ": " + props + "(unchanged)");
+            }
+            return false;
+        }
+
+        if (Ln.isEnabled(Ln.Level.VERBOSE)) {
+            Ln.v(getClass().getSimpleName() + ": "  + prev + " -> " + props);
+        }
+
+        return true;
+    }
+}