Add WSD protocol support

[Chrisimx]

[rw-django-fan-2020]

For Example: my Printer Canon MX490 does not support AirScan. It supports only WSD. How difficult is it to implement support for WSD?

[Chrisimx]

I've already created a library for interacting with WSD scanners. However, that still needs to be integrated into the app. Currently, I'm working on a refactoring that will make it easier to add further scanning protocols in the future (unfortunately, the app was originally quite dependent on eSCL as I didn't think I'd ever implement another protocol). I would like to take the time to make the architecture scalable for the forseeable future (which is quite cumbersome because all legacy app data has to be migrated) but WSD support is still planned to be part of the next release.

[Chrisimx]

I'm pleased to announce that a first alpha is now available, so you can test if the WSD implementation works with your scanners.

Please notice the following expected limitations:

• This is not considered ready for production use yet
• The scan region setting is not implemented yet
• It takes at minimum 3 seconds to discover a WSD scanner, so wait a bit before giving up. You can circumvent that by saving it as a custom scanner
• Creating Black-White scans using the built-in B&W color mode might not work because some scanners can not output B&W images in a JPEG
• Data from old ScanBridge versions is not properly migrated yet. Clear the data if the app crashes or you have had ScanBridge installed before
• There are currently no default settings chosen, so when you first enter the scan settings nothing maybe selected at all. The scanner will choose settings in that case

I'd be happy to here back from you if it works with your scanners :)

[jkhsjdhjs]

Wow, works well with my Brother MFC-J5320DW, thanks for your work on this! One thing I noticed that you didn't list as a limitation yet: In my case, the pixel density can only be set to 100, 200 or 300. However, the scanner supports up to 1200 DPI (although I'm not sure whether this applies to WSD as well). Again, thanks for your work here, it's incredible that WSD is now working at all!

[rw-django-fan-2020]

At the moment I cant test the WSD implementation. But my Scanner Brother DS‑940DW does work now with eSCL. Thank you, very much.

#112

[Chrisimx]

Wow, works well with my Brother MFC-J5320DW, thanks for your work on this! One thing I noticed that you didn't list as a limitation yet: In my case, the pixel density can only be set to 100, 200 or 300. However, the scanner supports up to 1200 DPI (although I'm not sure whether this applies to WSD as well). Again, thanks for your work here, it's incredible that WSD is now working at all!

@jkhsjdhjs Yeah, that is an interesting problem. My Brother scanner (Brother MFC-L8690CDW) also only reports to support 300dpi over WSD while the hardware actually supports 600dpi, so it seems to be a firmware bug in multiple Brother devices. However, if I tell it to scan with 600dpi over WSD mine does it just fine, so it is just doesn't report it's capabilities correctly. For some reason, manufacturers simply cannot implement these protocols correctly.

So, there would be multiple ways to fix the issue:

• you could make an option which allows you to freely choose parameters, just ignoring the capabilities
• you could create a repository of corrected capabilities
• or you could hardcode the specific cases, but there are most likely wayyyyy to many (if this is really a systematic problem)

@rw-django-fan-2020 Glad to hear that eSCL works now! I think your Brother scanner also supports more than 300dpi. So, if you at some point can try out WSD with it, it would be interesting to know if it has the same issue.

[jkhsjdhjs]

For some reason, manufacturers simply cannot implement these protocols correctly.

Yep, unfortunately that always seems to be the case with standards. For example, the Linux kernel has thousands of lines of code just to handle devices that don't implement USB or PCI correctly...
Maybe it's also intentional in this case, to get people to use the official Brother driver?

So, there would be multiple ways to fix the issue:

• you could make an option which allows you to freely choose parameters, just ignoring the capabilities
• you could create a repository of corrected capabilities
• or you could hardcode the specific cases, but there are most likely wayyyyy to many (if this is really a systematic problem)

How about a combination of the first and third approaches? For scanners with known incorrect capabilities, the available DPI settings could be hardcoded. At the same time, an option to ignore the reported capabilities and choose the DPI freely could be provided. That way, users can still work around issues with scanners that aren't covered by the hardcoded list.

[rw-django-fan-2020]

The flat scanner of printer canon pixma mx495 does work now with WSD. But when I click on settings for the scanner the app ScanBridge crashes. I get the following error:

java.util.NoSuchElementException: Collection contains no element matching the predicate.
at io.github.chrisimx.scanbridge.data.ui.ScanSettingsComposableStateHolder$selectedInputSourceCaps$1.invokeSuspend(ScanSettingsComposableStateHolder.kt:191)
at io.github.chrisimx.scanbridge.data.ui.ScanSettingsComposableStateHolder$selectedInputSourceCaps$1.invoke(ScanSettingsComposableStateHolder.kt:11)
at io.github.chrisimx.scanbridge.data.ui.ScanSettingsComposableStateHolder$selectedInputSourceCaps$1.invoke(ScanSettingsComposableStateHolder.kt:6)
at kotlinx.coroutines.flow.FlowKt__ZipKt$combine$1$1.invokeSuspend(Zip.kt:29)
at kotlinx.coroutines.flow.FlowKt__ZipKt$combine$1$1.invoke(Zip.kt:13)
at kotlinx.coroutines.flow.FlowKt__ZipKt$combine$1$1.invoke(Zip.kt:6)
at kotlinx.coroutines.flow.internal.CombineKt$combineInternal$2.invokeSuspend(Combine.kt:73)
at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:34)
at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:100)
at kotlinx.coroutines.EventLoop.processUnconfinedEvent(EventLoop.common.kt:65)
at kotlinx.coroutines.DispatchedTaskKt.resumeUnconfined(DispatchedTask.kt:243)
at kotlinx.coroutines.DispatchedTaskKt.dispatch(DispatchedTask.kt:147)
at kotlinx.coroutines.CancellableContinuationImpl.dispatchResume(CancellableContinuationImpl.kt:470)
at kotlinx.coroutines.CancellableContinuationImpl.resumeImpl$kotlinx_coroutines_core(CancellableContinuationImpl.kt:504)
at kotlinx.coroutines.CancellableContinuationImpl.resumeImpl$kotlinx_coroutines_core$default(CancellableContinuationImpl.kt:493)
at kotlinx.coroutines.CancellableContinuationImpl.resumeWith(CancellableContinuationImpl.kt:359)
at kotlinx.coroutines.flow.SharedFlowImpl.tryEmit(SharedFlow.kt:414)
at kotlinx.coroutines.flow.internal.SubscriptionCountStateFlow.increment(AbstractSharedFlow.kt:127)
at kotlinx.coroutines.flow.internal.AbstractSharedFlow.allocateSlot(AbstractSharedFlow.kt:65)
at kotlinx.coroutines.flow.StateFlowImpl.collect(StateFlow.kt:387)
at kotlinx.coroutines.flow.ReadonlyStateFlow.collect(Share.kt:2)
at androidx.compose.runtime.SnapshotStateKt__SnapshotFlowKt$collectAsState$1$1.invokeSuspend(SnapshotFlow.kt:72)
at androidx.compose.runtime.SnapshotStateKt__SnapshotFlowKt$collectAsState$1$1.invoke(SnapshotFlow.kt:8)
at androidx.compose.runtime.SnapshotStateKt__SnapshotFlowKt$collectAsState$1$1.invoke(SnapshotFlow.kt:4)
at androidx.compose.runtime.SnapshotStateKt__ProduceStateKt$produceState$3$1.invokeSuspend(ProduceState.kt:141)
at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:34)
at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:100)
at androidx.compose.ui.platform.AndroidUiDispatcher.performTrampolineDispatch(AndroidUiDispatcher.android.kt:79)
at androidx.compose.ui.platform.AndroidUiDispatcher.access$performTrampolineDispatch(AndroidUiDispatcher.android.kt:41)
at androidx.compose.ui.platform.AndroidUiDispatcher$dispatchCallback$1.run(AndroidUiDispatcher.android.kt:57)
at android.os.Handler.handleCallback(Handler.java:1095)
at android.os.Handler.dispatchMessageImpl(Handler.java:135)
at android.os.Handler.dispatchMessage(Handler.java:125)
at android.os.Looper.loopOnce(Looper.java:296)
at android.os.Looper.loop(Looper.java:397)
at android.app.ActivityThread.main(ActivityThread.java:9569)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:575)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:975)
Suppressed: kotlinx.coroutines.internal.DiagnosticCoroutineContextException: [StandaloneCoroutine{Cancelling}@e9f7aea, Dispatchers.Main.immediate]

[rw-django-fan-2020]

There is a second scanner for copies. Does it use WSD too?