Create "manifest_override" feature

[NathanaelA]

This allows an escape hatch to declare a custom AndroidManifest.xml file to be copied rather than have it be generated.

In my specific case their are several items that the current generator doesn't support , and this now makes this tool (at least in the Android Manifest) easily forward compatible immediately as if the generator doesn't work you can override it with your own.

[mzdk100]

Can you give an example? It's best to use generators to support those use cases, which is consistent with Rust's best practices of using unified manifest files.

[NathanaelA]

Yep, I specifically ran into a few issues that I can remember (and several more that I can't)

1. the android:requestLegacyExternalStorage="true" in the tool manifest generator is creating a child-node inside of <application> like <requestLegacyExternalStorage>true</...> rather than putting that as a key:value pair in the `' -- I don't know if that works for other people but it is NOT working for me on the Meta Quest -- I spent way to many HOURS wasting time trying to figure out why the prior version using cargo-ndk and own manifest was working yet moving to the cargo-apk2 was totally failing.

Manifests

Created by Cargo-APK2

<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.mgcarpet.vr"
          android:versionCode="16777472" android:versionName="0.1.0">
    <uses-sdk android:minSdkVersion="26" android:targetSdkVersion="29"/>
    <uses-feature android:name="android.hardware.vr.headtracking" android:required="true" android:version="1"/>
    <uses-feature android:name="com.oculus.feature.PASSTHROUGH" android:required="false"/>
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
    <application android:debuggable="false" android:label="Magic Carpet VR" android:extractNativeLibs="true">
        <android:allowNativeHeapPointerTagging/>
        <android:requestLegacyExternalStorage>true</android:requestLegacyExternalStorage>
        <meta-data android:name="com.oculus.supportedDevices" android:value="quest2|questpro|quest3|quest3s"/>
        <activity
                android:configChanges="density|keyboard|keyboardHidden|navigation|orientation|screenLayout|screenSize|uiMode"
                android:name="android.app.NativeActivity"
                android:screenOrientation="landscape" android:exported="true" android:resizeableActivity="false">
            <meta-data android:name="android.app.lib_name" android:value="mgc_app"/>
            <meta-data android:name="com.oculus.intent.category.VR" android:value="vr_only"/>
            <meta-data android:name="com.oculus.supportedDevices" android:value="quest2|questpro|quest3|quest3s"/>
            <intent-filter>
                <action android:name="android.intent.action.MAIN"/>
                <category android:name="android.intent.category.LAUNCHER"/>
                <category android:name="com.oculus.intent.category.VR"/>
            </intent-filter>
        </activity>
        <activity
                android:configChanges="density|keyboard|keyboardHidden|navigation|orientation|screenLayout|screenSize|uiMode"
                android:name="rust.jniminhelper.PermActivity"
                android:screenOrientation="landscape" android:resizeableActivity="false"/>
    </application>
</manifest>

Created by me:

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
          package="com.mgcarpet.vr"
          android:versionCode="1"
          android:versionName="0.1.0">

    <uses-sdk android:minSdkVersion="26" android:targetSdkVersion="29"/>

    <!-- VR headtracking required; Quest 3 always provides it -->
    <uses-feature
        android:name="android.hardware.vr.headtracking"
        android:required="true"
        android:version="1"/>

    <!-- Boundaryless application -->
    <uses-feature
            android:name="com.oculus.feature.BOUNDARYLESS_APP"
            android:required="true"/>

    <!-- Passthrough is optional — useful for future mixed-reality overlays -->
    <uses-feature
        android:name="com.oculus.feature.PASSTHROUGH"
        android:required="false"/>

    <!-- /sdcard/mgcarpet/baked/ game data — legacy full access under targetSdkVersion 29 (see above) -->
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

    <application
        android:label="Magic Carpet VR"
        android:requestLegacyExternalStorage="true"
        android:hasCode="true">

        <!--
          NativeActivity: the OS calls into the .so produced by mgc-app.
          lib_name must match the Cargo package name (hyphens → underscores).
        -->
        <activity
            android:name="android.app.NativeActivity"
            android:configChanges="density|keyboard|keyboardHidden|navigation|orientation|screenLayout|screenSize|uiMode"
            android:exported="true"
            android:resizeableActivity="false"
            android:screenOrientation="landscape">

            <meta-data
                android:name="android.app.lib_name"
                android:value="mgc_app"/>

            <!-- Main launcher + VR category: Quest OS launches this as a VR app -->
            <intent-filter>
                <action android:name="android.intent.action.MAIN"/>
                <category android:name="android.intent.category.LAUNCHER"/>
                <category android:name="com.oculus.intent.category.VR"/>
            </intent-filter>

            <!-- Tell the Meta runtime this is a VR-only application -->
            <meta-data
                android:name="com.oculus.intent.category.VR"
                android:value="vr_only"/>

        </activity>

        <activity
                android:configChanges="density|keyboard|keyboardHidden|navigation|orientation|screenLayout|screenSize|uiMode"
                android:name="rust.jniminhelper.PermActivity" android:screenOrientation="landscape"
                android:resizeableActivity="false"/>
    </application>
</manifest>

3. During my tests trying to figure things out, for one test I wanted to do; I needed access to "tools:support" on a uses-permissions which requires not only that extra support on the uses-permission, but also requires a change on the top level to add the tools xmlns. I might still need to do this in the future, if I find some reason I need to move to API 31, but currently keeping it at api 29 & using my own manifest fixes the permissions issue... FYI; tools:xxxx are valid attributes on many different nodes; the generator has zero support for the tools namespace.

4. Theme on "Activity" is missing. (Minor, but ran into it while trying to fix a different issue. 😆 )

5. Top level nodes: Queries, path-permissions, properties, and uses-library are all items I've used in past app's, none of these are supported in the generator.

In addition, if you look at:
https://developer.android.com/guide/topics/manifest/manifest-intro#reference
&
https://developer.android.com/guide/topics/manifest/application-element
&
https://developer.android.com/guide/topics/manifest/activity-element

There are a massive number of both top level nodes and key:values that aren't currently supported...

So having an escape hatch, seems like a reasonable feature request...

[mzdk100]

I can merge this PR to temporarily solve this scenario problem, but I need you to add instructions for adding this feature in the README.