jrshikoku/plugins/with-display-metrics-sync.js

const { withMainActivity } = require("@expo/config-plugins");

const MARKER = "syncDisplayMetricsForCurrentDisplay";

/**
 * Keep React Native's process-wide display metrics aligned with the Activity's
 * current display. Samsung DeX/freeform windows can use a different density
 * from the phone display that initialized React Native.
 *
 * On a single-display device the Activity and process densities are the same,
 * so this is a no-op for normal Android devices.
 */
const withDisplayMetricsSync = (config) =>
  withMainActivity(config, (config) => {
    const { language } = config.modResults;

    if (config.modResults.contents.includes(MARKER)) {
      return config;
    }

    if (language === "kt") {
      config.modResults.contents = patchKotlinActivity(
        config.modResults.contents,
      );
      return config;
    }

    if (language === "java") {
      config.modResults.contents = patchJavaActivity(
        config.modResults.contents,
      );
      return config;
    }

    throw new Error(
      "[withDisplayMetricsSync] Unsupported MainActivity language: " + language,
    );
  });

function patchKotlinActivity(contents) {
  let patched = addImport(contents, "import android.os.Build");
  patched = addImport(patched, "import android.view.Display");
  patched = addImport(
    patched,
    "import android.content.res.Configuration",
  );
  patched = addImport(
    patched,
    "import com.facebook.react.uimanager.DisplayMetricsHolder",
  );

  const onCreateCall = "super.onCreate(null)";
  if (!patched.includes(onCreateCall)) {
    throw new Error(
      "[withDisplayMetricsSync] MainActivity.kt does not contain the expected onCreate call",
    );
  }

  patched = patched.replace(
    onCreateCall,
    [
      MARKER + "()",
      onCreateCall,
      MARKER + "()",
      "    scheduleDisplayMetricsSync()",
    ].join("\n    "),
  );

  const method = [
    "",
    "  /**",
    "   * Re-read density from the display currently hosting this Activity.",
    "   * DeX can use a different density from the phone's main display.",
    "   */",
    "  private fun " + MARKER + "() {",
    "    try {",
    "      val currentDisplay = getCurrentDisplay()",
    "      val displayContext = currentDisplay?.let { createDisplayContext(it) } ?: this",
    "      DisplayMetricsHolder.initDisplayMetrics(displayContext)",
    "    } catch (_: Throwable) {",
    "      // The display can be temporarily unavailable during Activity startup.",
    "    }",
    "  }",
    "",
    "  private fun getCurrentDisplay(): Display? {",
    "    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) {",
    "      display?.let { return it }",
    "    }",
    "    return window.decorView.display",
    "  }",
    "",
    "  private fun scheduleDisplayMetricsSync() {",
    "    window.decorView.post {",
    "      " + MARKER + "()",
    "      window.decorView.requestLayout()",
    "    }",
    "  }",
    "",
    "  override fun onStart() {",
    "    " + MARKER + "()",
    "    super.onStart()",
    "  }",
    "",
    "  override fun onResume() {",
    "    " + MARKER + "()",
    "    super.onResume()",
    "  }",
    "",
    "  override fun onConfigurationChanged(newConfig: Configuration) {",
    "    " + MARKER + "()",
    "    super.onConfigurationChanged(newConfig)",
    "    scheduleDisplayMetricsSync()",
    "  }",
    "",
    "  override fun onWindowFocusChanged(hasFocus: Boolean) {",
    "    if (hasFocus) {",
    "      " + MARKER + "()",
    "    }",
    "    super.onWindowFocusChanged(hasFocus)",
    "    if (hasFocus) {",
    "      scheduleDisplayMetricsSync()",
    "    }",
    "  }",
    "",
  ].join("\n");

  return insertBeforeClassClosingBrace(patched, method);
}

function patchJavaActivity(contents) {
  let patched = addImport(contents, "import android.os.Build;");
  patched = addImport(patched, "import android.view.Display;");
  patched = addImport(
    patched,
    "import android.content.res.Configuration;",
  );
  patched = addImport(patched, "import android.content.Context;");
  patched = addImport(
    patched,
    "import com.facebook.react.uimanager.DisplayMetricsHolder;",
  );

  const onCreateCall = "super.onCreate(null);";
  if (!patched.includes(onCreateCall)) {
    throw new Error(
      "[withDisplayMetricsSync] MainActivity.java does not contain the expected onCreate call",
    );
  }

  patched = patched.replace(
    onCreateCall,
    [
      MARKER + "();",
      onCreateCall,
      MARKER + "();",
      "    scheduleDisplayMetricsSync();",
    ].join("\n    "),
  );

  const method = [
    "",
    "  /**",
    "   * Re-read density from the display currently hosting this Activity.",
    "   * DeX can use a different density from the phone's main display.",
    "   */",
    "  private void " + MARKER + "() {",
    "    try {",
    "      Display currentDisplay = getCurrentDisplay();",
    "      Context displayContext = currentDisplay != null",
    "          ? createDisplayContext(currentDisplay)",
    "          : this;",
    "      DisplayMetricsHolder.initDisplayMetrics(displayContext);",
    "    } catch (Throwable ignored) {",
    "      // The display can be temporarily unavailable during Activity startup.",
    "    }",
    "  }",
    "",
    "  private Display getCurrentDisplay() {",
    "    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) {",
    "      Display activityDisplay = getDisplay();",
    "      if (activityDisplay != null) {",
    "        return activityDisplay;",
    "      }",
    "    }",
    "    return getWindow().getDecorView().getDisplay();",
    "  }",
    "",
    "  private void scheduleDisplayMetricsSync() {",
    "    getWindow().getDecorView().post(() -> {",
    "      " + MARKER + "();",
    "      getWindow().getDecorView().requestLayout();",
    "    });",
    "  }",
    "",
    "  @Override",
    "  protected void onStart() {",
    "    " + MARKER + "();",
    "    super.onStart();",
    "  }",
    "",
    "  @Override",
    "  protected void onResume() {",
    "    " + MARKER + "();",
    "    super.onResume();",
    "  }",
    "",
    "  @Override",
    "  public void onConfigurationChanged(Configuration newConfig) {",
    "    " + MARKER + "();",
    "    super.onConfigurationChanged(newConfig);",
    "    scheduleDisplayMetricsSync();",
    "  }",
    "",
    "  @Override",
    "  public void onWindowFocusChanged(boolean hasFocus) {",
    "    if (hasFocus) {",
    "      " + MARKER + "();",
    "    }",
    "    super.onWindowFocusChanged(hasFocus);",
    "    if (hasFocus) {",
    "      scheduleDisplayMetricsSync();",
    "    }",
    "  }",
    "",
  ].join("\n");

  return insertBeforeClassClosingBrace(patched, method);
}

function addImport(contents, importLine) {
  if (contents.includes(importLine)) {
    return contents;
  }

  const packageStart = contents.indexOf("package ");
  const packageEnd = contents.indexOf("\n", packageStart);
  if (packageStart < 0 || packageEnd < 0) {
    throw new Error(
      "[withDisplayMetricsSync] Could not find package declaration while adding " +
        importLine,
    );
  }

  return (
    contents.slice(0, packageEnd + 1) +
    "\n" +
    importLine +
    "\n" +
    contents.slice(packageEnd + 1)
  );
}

function insertBeforeClassClosingBrace(contents, block) {
  const closingBrace = contents.lastIndexOf("\n}");
  if (closingBrace < 0) {
    throw new Error(
      "[withDisplayMetricsSync] Could not find MainActivity class closing brace",
    );
  }

  return contents.slice(0, closingBrace) + block + contents.slice(closingBrace);
}

module.exports = withDisplayMetricsSync;