Update base density for external displays to achieve 10.4mm touch target

size

Flag: com.android.server.display.feature.flags.base_density_for_external_displays
Test: atest LocalDisplayAdapterTest
Bug: 392854227
Change-Id: I93615a6f4a53c6b8790acc527b6d2c90e1a4d89f

2 files changed, 13 insertions, 5 deletions

diff --git a/services/core/java/com/android/server/display/LocalDisplayAdapter.java b/services/core/java/com/android/server/display/LocalDisplayAdapter.java
index 83ca563e0534..324f95a5974b 100644
--- a/services/core/java/com/android/server/display/LocalDisplayAdapter.java
+++ b/services/core/java/com/android/server/display/LocalDisplayAdapter.java
@@ -35,6 +35,7 @@ import android.os.Looper;
 import android.os.PowerManager;
 import android.os.SystemProperties;
 import android.os.Trace;
+import android.util.DisplayMetrics;
 import android.util.DisplayUtils;
 import android.util.LongSparseArray;
 import android.util.Slog;
@@ -84,6 +85,10 @@ final class LocalDisplayAdapter extends DisplayAdapter {
     private static final String PROPERTY_EMULATOR_CIRCULAR = "ro.boot.emulator.circular";
 
     private static final double DEFAULT_DISPLAY_SIZE = 24.0;
+    // Touch target size 10.4mm in inches (divided by mm per inch 25.4)
+    private static final double EXTERNAL_DISPLAY_BASE_TOUCH_TARGET_SIZE_IN_INCHES = 10.4 / 25.4;
+
+    private static final double BASE_TOUCH_TARGET_SIZE_DP = 48.0;
 
     private final LongSparseArray<LocalDisplayDevice> mDevices = new LongSparseArray<>();
 
@@ -530,17 +535,20 @@ final class LocalDisplayAdapter extends DisplayAdapter {
             if (densityMapping == null) {
                 if (getFeatureFlags().isBaseDensityForExternalDisplaysEnabled()
                         && !mStaticDisplayInfo.isInternal) {
-                    double dpi;
+                    double ppi;
 
                     if (mActiveSfDisplayMode.xDpi > 0 && mActiveSfDisplayMode.yDpi > 0) {
-                        dpi = Math.sqrt((Math.pow(mActiveSfDisplayMode.xDpi, 2)
+                        ppi = Math.sqrt((Math.pow(mActiveSfDisplayMode.xDpi, 2)
                                 + Math.pow(mActiveSfDisplayMode.yDpi, 2)) / 2);
                     } else {
                         // xDPI and yDPI is missing, calculate DPI from display resolution and
                         // default display size
-                        dpi = Math.sqrt(Math.pow(mInfo.width, 2) + Math.pow(mInfo.height, 2))
+                        ppi = Math.sqrt(Math.pow(mInfo.width, 2) + Math.pow(mInfo.height, 2))
                                 / DEFAULT_DISPLAY_SIZE;
                     }
+                    double pixels = ppi * EXTERNAL_DISPLAY_BASE_TOUCH_TARGET_SIZE_IN_INCHES;
+                    double dpi =
+                            pixels * DisplayMetrics.DENSITY_DEFAULT / BASE_TOUCH_TARGET_SIZE_DP;
                     return (int) (dpi + 0.5);
                 }
                 return (int) (mStaticDisplayInfo.density * 160 + 0.5);
diff --git a/services/tests/displayservicetests/src/com/android/server/display/LocalDisplayAdapterTest.java b/services/tests/displayservicetests/src/com/android/server/display/LocalDisplayAdapterTest.java
index b9cea0c72306..f8b4113a3c04 100644
--- a/services/tests/displayservicetests/src/com/android/server/display/LocalDisplayAdapterTest.java
+++ b/services/tests/displayservicetests/src/com/android/server/display/LocalDisplayAdapterTest.java
@@ -550,10 +550,10 @@ public class LocalDisplayAdapterTest {
 
         assertDisplayDpi(
                 mListener.addedDisplays.get(0).getDisplayDeviceInfoLocked(), PORT_A, 100, 100,
-                100);
+                136);
         assertDisplayDpi(
                 mListener.addedDisplays.get(1).getDisplayDeviceInfoLocked(), PORT_B, 100, 100,
-                100);
+                136);
     }
 
     private static class DisplayModeWrapper {