added fallback getting displayInfo when displayInfo is null

server/src/main/java/com/genymobile/scrcpy/Command.java

@@ -30,4 +30,14 @@ public static String execReadLine(String... cmd) throws IOException, Interrupted
         }
         return result;
     }
+
+    public static String execReadOutput(String... cmd) throws IOException, InterruptedException {
+        Process process = Runtime.getRuntime().exec(cmd);
+        String output = IO.toString(process.getInputStream());
+        int exitCode = process.waitFor();
+        if (exitCode != 0) {
+            throw new IOException("Command " + Arrays.toString(cmd) + " returned with value " + exitCode);
+        }
+        return output;
+    }
 }

server/src/main/java/com/genymobile/scrcpy/IO.java

@@ -6,7 +6,9 @@
 
 import java.io.FileDescriptor;
 import java.io.IOException;
+import java.io.InputStream;
 import java.nio.ByteBuffer;
+import java.util.Scanner;
 
 public final class IO {
     private IO() {
@@ -37,4 +39,13 @@ public static void writeFully(FileDescriptor fd, ByteBuffer from) throws IOExcep
     public static void writeFully(FileDescriptor fd, byte[] buffer, int offset, int len) throws IOException {
         writeFully(fd, ByteBuffer.wrap(buffer, offset, len));
     }
+
+    public static String toString(InputStream inputStream) {
+        StringBuilder builder = new StringBuilder();
+        Scanner scanner = new Scanner(inputStream);
+        while (scanner.hasNextLine()) {
+            builder.append(scanner.nextLine()).append('\n');
+        }
+        return builder.toString();
+    }
 }

server/src/main/java/com/genymobile/scrcpy/wrappers/DisplayManager.java

@@ -1,20 +1,74 @@
 package com.genymobile.scrcpy.wrappers;
 
+import com.genymobile.scrcpy.Command;
 import com.genymobile.scrcpy.DisplayInfo;
+import com.genymobile.scrcpy.Ln;
 import com.genymobile.scrcpy.Size;
 
+import android.view.Display;
+
+import java.lang.reflect.Field;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
 public final class DisplayManager {
     private final Object manager; // instance of hidden class android.hardware.display.DisplayManagerGlobal
 
     public DisplayManager(Object manager) {
         this.manager = manager;
     }
 
+    // public to call it from unit tests
+    public static DisplayInfo parseDisplayInfo(String dumpsysDisplayOutput, int displayId) {
+        Pattern regex = Pattern.compile(
+                "^    mBaseDisplayInfo=DisplayInfo\\{\".*\", displayId " + displayId + ".*?(, FLAG_.*)?, real ([0-9]+) x ([0-9]+).*, rotation ([0-9]+)"
+                        + ".*, layerStack ([0-9]+)",
+                Pattern.MULTILINE);
+        Matcher m = regex.matcher(dumpsysDisplayOutput);
+        if (!m.find()) {
+            return null;
+        }
+        int flags = parseDisplayFlags(m.group(1));
+        int width = Integer.parseInt(m.group(2));
+        int height = Integer.parseInt(m.group(3));
+        int rotation = Integer.parseInt(m.group(4));
+        int layerStack = Integer.parseInt(m.group(5));
+
+        return new DisplayInfo(displayId, new Size(width, height), rotation, layerStack, flags);
+    }
+
+    private static DisplayInfo getDisplayInfoFromDumpsysDisplay(int displayId) {
+        try {
+            String dumpsysDisplayOutput = Command.execReadOutput("dumpsys", "display");
+            return parseDisplayInfo(dumpsysDisplayOutput, displayId);
+        } catch (Exception e) {
+            Ln.e("Could not get display info from \"dumpsys display\" output", e);
+            return null;
+        }
+    }
+
+    private static int parseDisplayFlags(String text) {
+        Pattern regex = Pattern.compile("FLAG_[A-Z_]+");
+        Matcher m = regex.matcher(text);
+        int flags = 0;
+        while (m.find()) {
+            String flagString = m.group();
+            try {
+                Field filed = Display.class.getDeclaredField(flagString);
+                flags |= filed.getInt(null);
+            } catch (NoSuchFieldException | IllegalAccessException e) {
+                // Silently ignore, some flags reported by "dumpsys display" are @TestApi
+            }
+        }
+        return flags;
+    }
+
     public DisplayInfo getDisplayInfo(int displayId) {
         try {
             Object displayInfo = manager.getClass().getMethod("getDisplayInfo", int.class).invoke(manager, displayId);
-            if (displayInfo == null) {
-                return null;
+            if (displayInfo != null) {
+                // fallback when displayInfo is null
+                return getDisplayInfoFromDumpsysDisplay(displayId);
             }
             Class<?> cls = displayInfo.getClass();
             // width and height already take the rotation into account

server/src/test/java/com/genymobile/scrcpy/CommandParserTest.java

@@ -0,0 +1,98 @@
+package com.genymobile.scrcpy;
+
+import com.genymobile.scrcpy.wrappers.DisplayManager;
+
+import android.view.Display;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class CommandParserTest {
+    @Test
+    public void testParseDisplayInfoFrqomDumpsysDisplay() {
+        /* @formatter:off */
+        String partialOutput = "Logical Displays: size=1\n"
+                + "  Display 0:\n"
+                + "mDisplayId=0\n"
+                + "    mLayerStack=0\n"
+                + "    mHasContent=true\n"
+                + "    mDesiredDisplayModeSpecs={baseModeId=2 primaryRefreshRateRange=[90 90] appRequestRefreshRateRange=[90 90]}\n"
+                + "    mRequestedColorMode=0\n"
+                + "    mDisplayOffset=(0, 0)\n"
+                + "    mDisplayScalingDisabled=false\n"
+                + "    mPrimaryDisplayDevice=Built-in Screen\n"
+                + "    mBaseDisplayInfo=DisplayInfo{\"Built-in Screen\", displayId 0, FLAG_SECURE, FLAG_SUPPORTS_PROTECTED_BUFFERS, FLAG_TRUSTED, "
+                + "real 1440 x 3120, largest app 1440 x 3120, smallest app 1440 x 3120, appVsyncOff 2000000, presDeadline 11111111, mode 2, "
+                + "defaultMode 1, modes [{id=1, width=1440, height=3120, fps=60.0}, {id=2, width=1440, height=3120, fps=90.0}, {id=3, width=1080, "
+                + "height=2340, fps=90.0}, {id=4, width=1080, height=2340, fps=60.0}], hdrCapabilities HdrCapabilities{mSupportedHdrTypes=[2, 3, 4], "
+                + "mMaxLuminance=540.0, mMaxAverageLuminance=270.1, mMinLuminance=0.2}, minimalPostProcessingSupported false, rotation 0, state OFF, "
+                + "type INTERNAL, uniqueId \"local:0\", app 1440 x 3120, density 600 (515.154 x 514.597) dpi, layerStack 0, colorMode 0, "
+                + "supportedColorModes [0, 7, 9], address {port=129, model=0}, deviceProductInfo DeviceProductInfo{name=, manufacturerPnpId=QCM, "
+                + "productId=1, modelYear=null, manufactureDate=ManufactureDate{week=27, year=2006}, relativeAddress=null}, removeMode 0}\n"
+                + "    mOverrideDisplayInfo=DisplayInfo{\"Built-in Screen\", displayId 0, FLAG_SECURE, FLAG_SUPPORTS_PROTECTED_BUFFERS, "
+                + "FLAG_TRUSTED, real 1440 x 3120, largest app 3120 x 2983, smallest app 1440 x 1303, appVsyncOff 2000000, presDeadline 11111111, "
+                + "mode 2, defaultMode 1, modes [{id=1, width=1440, height=3120, fps=60.0}, {id=2, width=1440, height=3120, fps=90.0}, {id=3, "
+                + "width=1080, height=2340, fps=90.0}, {id=4, width=1080, height=2340, fps=60.0}], hdrCapabilities "
+                + "HdrCapabilities{mSupportedHdrTypes=[2, 3, 4], mMaxLuminance=540.0, mMaxAverageLuminance=270.1, mMinLuminance=0.2}, "
+                + "minimalPostProcessingSupported false, rotation 0, state ON, type INTERNAL, uniqueId \"local:0\", app 1440 x 3120, density 600 "
+                + "(515.154 x 514.597) dpi, layerStack 0, colorMode 0, supportedColorModes [0, 7, 9], address {port=129, model=0}, deviceProductInfo "
+                + "DeviceProductInfo{name=, manufacturerPnpId=QCM, productId=1, modelYear=null, manufactureDate=ManufactureDate{week=27, year=2006}, "
+                + "relativeAddress=null}, removeMode 0}\n"
+                + "    mRequestedMinimalPostProcessing=false\n";
+        DisplayInfo displayInfo = DisplayManager.parseDisplayInfo(partialOutput, 0);
+        Assert.assertNotNull(displayInfo);
+        Assert.assertEquals(0, displayInfo.getDisplayId());
+        Assert.assertEquals(0, displayInfo.getRotation());
+        Assert.assertEquals(0, displayInfo.getLayerStack());
+        // FLAG_TRUSTED does not exist in Display (@TestApi), so it won't be reported
+        Assert.assertEquals(Display.FLAG_SECURE | Display.FLAG_SUPPORTS_PROTECTED_BUFFERS, displayInfo.getFlags());
+        Assert.assertEquals(1440, displayInfo.getSize().getWidth());
+        Assert.assertEquals(3120, displayInfo.getSize().getHeight());
+    }
+
+    @Test
+    public void testParseDisplayInfoFrqomDumpsysDisplayAPI31() {
+        /* @formatter:off */
+        String partialOutput = "Logical Displays: size=1\n"
+                + "  Display 0:\n"
+                + "    mDisplayId=0\n"
+                + "    mPhase=1\n"
+                + "    mLayerStack=0\n"
+                + "    mHasContent=true\n"
+                + "    mDesiredDisplayModeSpecs={baseModeId=1 allowGroupSwitching=false primaryRefreshRateRange=[0 60] appRequestRefreshRateRange=[0 Infinity]}\n"
+                + "    mRequestedColorMode=0\n"
+                + "    mDisplayOffset=(0, 0)\n"
+                + "    mDisplayScalingDisabled=false\n"
+                + "    mPrimaryDisplayDevice=Built-in Screen\n"
+                + "    mBaseDisplayInfo=DisplayInfo{\"Built-in Screen\", displayId 0\", displayGroupId 0, FLAG_SECURE, FLAG_SUPPORTS_PROTECTED_BUFFERS"
+                + ", FLAG_TRUSTED, real 1080 x 2280, largest app 1080 x 2280, smallest app 1080 x 2280, appVsyncOff 1000000, presDeadline 16666666, "
+                + "mode 1, defaultMode 1, modes [{id=1, width=1080, height=2280, fps=60.000004, alternativeRefreshRates=[]}], "
+                + "hdrCapabilities HdrCapabilities{mSupportedHdrTypes=[], mMaxLuminance=500.0, mMaxAverageLuminance=500.0, mMinLuminance=0.0}, "
+                + "userDisabledHdrTypes [], minimalPostProcessingSupported false, rotation 0, state ON, type INTERNAL, uniqueId \"local:4619827259835644672\", "
+                + "app 1080 x 2280, density 440 (440.0 x 440.0) dpi, layerStack 0, colorMode 0, supportedColorModes [0], address {port=0, model=0x401cec6a7a2b7b}, "
+                + "deviceProductInfo DeviceProductInfo{name=EMU_display_0, manufacturerPnpId=GGL, productId=1, modelYear=null, "
+                + "manufactureDate=ManufactureDate{week=27, year=2006}, connectionToSinkType=0}, removeMode 0, refreshRateOverride 0.0, "
+                + "brightnessMinimum 0.0, brightnessMaximum 1.0, brightnessDefault 0.39763778}\n"
+                + "    mOverrideDisplayInfo=DisplayInfo{\"Built-in Screen\", displayId 0\", displayGroupId 0, FLAG_SECURE, FLAG_SUPPORTS_PROTECTED_BUFFERS, "
+                + "FLAG_TRUSTED, real 1080 x 2280, largest app 2148 x 2065, smallest app 1080 x 997, appVsyncOff 1000000, presDeadline 16666666, mode 1, "
+                + "defaultMode 1, modes [{id=1, width=1080, height=2280, fps=60.000004, alternativeRefreshRates=[]}], hdrCapabilities HdrCapabilities{"
+                + "mSupportedHdrTypes=[], mMaxLuminance=500.0, mMaxAverageLuminance=500.0, mMinLuminance=0.0}, userDisabledHdrTypes [], "
+                + "minimalPostProcessingSupported false, rotation 0, state ON, type INTERNAL, uniqueId \"local:4619827259835644672\", app 1080 x 2148, "
+                + "density 440 (440.0 x 440.0) dpi, layerStack 0, colorMode 0, supportedColorModes [0], address {port=0, model=0x401cec6a7a2b7b}, "
+                + "deviceProductInfo DeviceProductInfo{name=EMU_display_0, manufacturerPnpId=GGL, productId=1, modelYear=null, "
+                + "manufactureDate=ManufactureDate{week=27, year=2006}, connectionToSinkType=0}, removeMode 0, refreshRateOverride 0.0, "
+                + "brightnessMinimum 0.0, brightnessMaximum 1.0, brightnessDefault 0.39763778}\n"
+                + "    mRequestedMinimalPostProcessing=false\n"
+                + "    mFrameRateOverrides=[]\n"
+                + "    mPendingFrameRateOverrideUids={}\n";
+        DisplayInfo displayInfo = DisplayManager.parseDisplayInfo(partialOutput, 0);
+        Assert.assertNotNull(displayInfo);
+        Assert.assertEquals(0, displayInfo.getDisplayId());
+        Assert.assertEquals(0, displayInfo.getRotation());
+        Assert.assertEquals(0, displayInfo.getLayerStack());
+        // FLAG_TRUSTED does not exist in Display (@TestApi), so it won't be reported
+        Assert.assertEquals(Display.FLAG_SECURE | Display.FLAG_SUPPORTS_PROTECTED_BUFFERS, displayInfo.getFlags());
+        Assert.assertEquals(1080, displayInfo.getSize().getWidth());
+        Assert.assertEquals(2280, displayInfo.getSize().getHeight());
+    }
+}