feat(doc-scan): Query for FairScan, if built-in scanning not available by PhilLab · Pull Request #16427 · nextcloud/android

PhilLab · 2026-02-01T14:04:09Z

Tests written, or not not needed

Built-in scanning is not available for all build variants - e.g. not for "generic", which is the flavor for the F-Droid release. It doesn't allow the non-reproducible TinyOpenCV build.

If this is the case, we are checking whether the open source scanning app FairScan is available (https://github.com/pynicolas/FairScan) and open that one for scanning.

This approach was selected based on the discussion here: #12624 (comment)

Result

Screen_recording_20260201_143916.webm

I thought about giving this menu entry a dedicated title, e.g. "Scan document from FairScan", but I decided against it - it's just more code to maintain and at the same time doesn't provide value to the user. Also it is not scalable: what if we add fallbacks to other scanner apps as well? So let's stick to the standard menu entry text.
I also had in mind to make this menu entry an "Install FairScan" button, in case there is no appscan and FairScan also is not installed. But that felt too intrusive.

Behind the scenes

To simplify the detection of the appscan project, a reflection-based approach was implemented. See the messages of the first two commits for why I am proposing this. If you don't agree with this approach, I can remove the commits from the PR, they don't impact the feature itself
FairScan delivers a short-lived URI which we then use to upload the file. Originally, the filename is an "ugly" unix timestamp - you can also see this in above recording, from a prior attempt: 1769952395766.pdf.
- To make this a little prettier, the filename is transformed to our standard timestamped name, just like we do for images and videos captured via the camera intent.
- Technically, this is done with the same approach of a fileDisplayNameTransformer as in my other current PR When uploading a single file, offer input field to change file name #16298.
Notably, FairScan's Intent feature is still experimental (see their README) but I'd still propose to include it, because:
- For Non-F-Droid users, all stays the same and uses the built-in scanner
- For F-Droid users, the menu entry will only appear if FairScan is installed, so the area of impact is quite small.
- The intent integration is very basic so it is not very likely that FairScan's next iteration will change it in a way which is incompatible with this.
- If it breaks by changing the intent URI - the button will simply not show anymore so we are not worse off than the status-quo.
- If it breaks otherwise, then we are still not worse off than having no scanner in the F-Droid variant at all.

alperozturk96 · 2026-02-12T10:47:22Z

@tobiasKaminsky What do you think, could you share your opinion?

github-actions · 2026-02-16T02:12:56Z

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PhilLab · 2026-03-01T18:33:57Z

@tobiasKaminsky @alperozturk96 can you let me know your thoughts about the implementation?
As I said, I can easily drop the reflection-based appscan check, if you think this is entirely the wrong direction. It has its pros and cons, as explained in the respective commit message.

tobiasKaminsky · 2026-03-02T07:05:50Z

I checked again with Fdroid, if we could use tiny cv:
https://gitlab.com/fdroid/fdroiddata/-/issues/3822

But since this will not work / is too complicated, I am fine with this approach ✔

alperozturk96 · 2026-03-02T09:07:22Z

app/src/androidTestGeneric/java/com/nextcloud/client/di/VariantModuleTest.kt

+        }
+    }
+
+    /**


Please remove unnecessary comment since interface and what it does already clear.

alperozturk96 · 2026-03-02T09:07:40Z

app/src/androidTestGeneric/java/com/nextcloud/client/di/VariantModuleTest.kt

+        assertFalse(feature.isAvailable)
+        assertEquals(AppScanOptionalFeature.Stub, feature)
+
+        // Verify that calling getScanContract on stub throws UnsupportedOperationException


Please remove comment logic already explains itself.

alperozturk96 · 2026-03-02T09:08:02Z

app/src/androidTestGplay/java/com/nextcloud/client/di/VariantModuleTest.kt

+    }
+
+    /**
+     * Dagger component for testing VariantModule in isolation


Please remove unnecessary comment since interface and what it does already clear.

alperozturk96 · 2026-03-02T09:10:37Z

app/src/androidTestGeneric/java/com/nextcloud/client/di/VariantModuleTest.kt

+     * In this variant, app scan should not be available
+     */
+    @Test
+    fun testAppScanOptionalFeatureAvailability() {


Please rename function name to testAppScanWhenNotAvailableShouldReturnError and remove function comment.

alperozturk96 · 2026-03-02T09:11:06Z

app/src/androidTestGplay/java/com/nextcloud/client/di/VariantModuleTest.kt

+     * In this variant, app scan should be available
+     */
+    @Test
+    fun testAppScanOptionalFeatureAvailability() {


Please rename function name to testAppScanWhenAvailableShouldReturnContract and remove function comment.

alperozturk96 · 2026-03-02T09:11:26Z

app/src/androidTestGplay/java/com/nextcloud/client/di/VariantModuleTest.kt

+        assertTrue(feature.isAvailable)
+        assertNotEquals(AppScanOptionalFeature.Stub, feature)
+
+        // Verify that calling getScanContract returns without raising an exception


Please remove the comment. Since function name will be changed and what it is doing clear.

alperozturk96 · 2026-03-02T09:12:59Z

app/src/main/java/com/owncloud/android/ui/activity/FileDisplayActivity.kt


        val currentDir = getCurrentDir()
        val remotePath = if (currentDir != null) currentDir.remotePath else OCFile.ROOT_PATH
+        var fileDisplayNameTransformer: androidx.core.util.Function<Uri, String?>? = null


Please remove or simplify androidx.core.util.Function<Uri, String?>? variable type if possible.

alperozturk96 · 2026-03-02T09:16:15Z

app/src/main/java/com/owncloud/android/ui/fragment/OCFileListFragment.java

    private FloatingActionButton mFabMain;
    public static boolean isMultipleFileSelectedForCopyOrMove = false;

+    private static final Intent mFairScanIntent = new Intent("org.fairscan.app.action.SCAN_TO_PDF");


mFairScanIntent please replace this variable name to scanIntent.

I suggest to avoid using m prefix for new variable names to match with rest of the code. Also no need to indicate specific package name in the variable since it's is just a scan intent.

@alperozturk96 renamed, though made it explicit in the new name that it is an external app. This way you cannot confuse it with any internal intent.

alperozturk96 · 2026-03-02T09:19:02Z

app/src/main/AndroidManifest.xml

+        <intent>
+            <!-- Since Android 11 (API level 30), this is required to detect the availability of FairScan to use
+             for external document scanning. See https://developer.android.com/training/package-visibility -->
+            <action android:name="org.fairscan.app.action.SCAN_TO_PDF" />


Please remove the comment.

<action android:name="org.fairscan.app.action.SCAN_TO_PDF" /> this already explains to developer what it is doing.

@alperozturk96 I moved it up and adjusted a little to fit the other declarations

PhilLab · 2026-03-02T18:01:01Z

@alperozturk96 thanks for the helpful review, I force-pushed an update just now.

To enable the document scanning feature for a specific build variant, previously two places had to be adjusted: - The build.gradle.kts, in the "region AppScan" - A variant-specific implementation for VariantModule.kt Now, only the first one is required and the VariantModule.kt handles it automatically. Benefits: Only a single place to change. And no code duplication Drawback: Reflection is a bit more brittle - it all depends on the package and class name to not change Signed-off-by: Philipp Hasper <vcs@hasper.info>

Testing two main variants, one without appscan, and one with it. However, as of now the automated test for the gplay flavor does not run automatically in the CI, as we only test the generic flavor. So the test's purpose was just to verify the reflection approach locally. Signed-off-by: Philipp Hasper <vcs@hasper.info>

Built-in scanning is not available for all build variants - e.g. not for "generic", which is the flavor for the F-Droid release. It doesn't allow the non-reproducible TinyOpenCV build. If this is the case, we are checking whether the open source scanning app FairScan is available (https://github.com/pynicolas/FairScan) and open that one for scanning. The declaration in the AndroidManifest is required since Android 11 (API level 30), otherwise the Intent would always be null. See https://developer.android.com/training/package-visibility Signed-off-by: Philipp Hasper <vcs@hasper.info>

Before, the filename from FairScan just was <unixTimestamp>.pdf. Now, we are giving it our own timestamped name, just like we do for images and videos captured via the camera intent. This uses the same fileDisplayNameTransformer as PR #16298 Signed-off-by: Philipp Hasper <vcs@hasper.info>

github-actions · 2026-03-03T09:03:28Z

blue-Light-Screenshot test failed, but no output was generated. Maybe a preliminary stage failed.

github-actions · 2026-03-03T09:03:29Z

Codacy

SpotBugs

Category	Base	New
Bad practice	42	42
Correctness	75	75
Dodgy code	253	253
Experimental	1	1
Internationalization	7	7
Malicious code vulnerability	2	2
Multithreaded correctness	34	34
Performance	43	43
Security	18	18
Total	475	475

github-actions · 2026-03-03T09:03:42Z

APK file: https://www.kaminsky.me/nc-dev/android-artifacts/16427.apk

To test this change/fix you can simply download above APK file and install and test it in parallel to your existing Nextcloud app.

PhilLab requested review from alperozturk96 and tobiasKaminsky February 1, 2026 14:04

PhilLab added enhancement 3. to review feature: files labels Feb 1, 2026

PhilLab changed the title ~~If built-in scanning is not available, check for FairScan~~ Use FairScan, if built-in document scanning is not available Feb 1, 2026

PhilLab mentioned this pull request Feb 1, 2026

Offer FairScan as a library to be included in other apps pynicolas/FairScan#87

Closed

PhilLab changed the title ~~Use FairScan, if built-in document scanning is not available~~ feat(doc-scan): Query for FairScan, if built-in scanning not available Feb 2, 2026

github-actions bot added the feedback-requested label Feb 16, 2026

PhilLab force-pushed the ph/document_scanning_external branch from e169423 to 25b3249 Compare March 1, 2026 18:31

alperozturk96 force-pushed the ph/document_scanning_external branch from 25b3249 to 825f386 Compare March 2, 2026 08:58

alperozturk96 requested changes Mar 2, 2026

View reviewed changes

PhilLab force-pushed the ph/document_scanning_external branch from 825f386 to 6bfe459 Compare March 2, 2026 17:58

PhilLab requested a review from alperozturk96 March 2, 2026 18:00

PhilLab added 4 commits March 3, 2026 09:52

alperozturk96 force-pushed the ph/document_scanning_external branch from 6bfe459 to 94d5e7a Compare March 3, 2026 08:52

alperozturk96 approved these changes Mar 3, 2026

View reviewed changes

alperozturk96 merged commit 2da4633 into master Mar 3, 2026
17 of 20 checks passed

alperozturk96 deleted the ph/document_scanning_external branch March 3, 2026 09:00

+                      }
+                  }
+                  /**

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