fix: do not crash when getting NaN on Android

CHANGELOG.md

@@ -1,5 +1,6 @@
 ## NEXT
-* Fixed a leak of the barcode scanner on Android.
+* [Android] Fixed a leak of the barcode scanner.
+* [Android] Fixed a crash when encountering invalid numbers for the scan window.
 
 ## 5.1.1
 * This release fixes an issue with automatic starts in the examples.

android/src/main/kotlin/dev/steenbakker/mobile_scanner/MobileScanner.kt

@@ -170,25 +170,35 @@ class MobileScanner(
         return Bitmap.createBitmap(bitmap, 0, 0, bitmap.width, bitmap.height, matrix, true)
     }
 
-    // scales the scanWindow to the provided inputImage and checks if that scaled
-    // scanWindow contains the barcode
-    private fun isBarcodeInScanWindow(
+    // Scales the scanWindow to the provided inputImage and checks if that scaled
+    // scanWindow contains the barcode.
+    @VisibleForTesting
+    fun isBarcodeInScanWindow(
         scanWindow: List<Float>,
         barcode: Barcode,
         inputImage: ImageProxy
     ): Boolean {
+        // TODO: use `cornerPoints` instead, since the bounding box is not bound to the coordinate system of the input image
+        // On iOS we do this correctly, so the calculation should match that.
         val barcodeBoundingBox = barcode.boundingBox ?: return false
 
-        val imageWidth = inputImage.height
-        val imageHeight = inputImage.width
+        try {
+            val imageWidth = inputImage.height
+            val imageHeight = inputImage.width
 
-        val left = (scanWindow[0] * imageWidth).roundToInt()
-        val top = (scanWindow[1] * imageHeight).roundToInt()
-        val right = (scanWindow[2] * imageWidth).roundToInt()
-        val bottom = (scanWindow[3] * imageHeight).roundToInt()
+            val left = (scanWindow[0] * imageWidth).roundToInt()
+            val top = (scanWindow[1] * imageHeight).roundToInt()
+            val right = (scanWindow[2] * imageWidth).roundToInt()
+            val bottom = (scanWindow[3] * imageHeight).roundToInt()
 
-        val scaledScanWindow = Rect(left, top, right, bottom)
-        return scaledScanWindow.contains(barcodeBoundingBox)
+            val scaledScanWindow = Rect(left, top, right, bottom)
+
+            return scaledScanWindow.contains(barcodeBoundingBox)
+        } catch (exception: IllegalArgumentException) {
+            // Rounding of the scan window dimensions can fail, due to encountering NaN.
+            // If we get NaN, rather than give a false positive, just return false.
+            return false
+        }
     }
 
     // Return the best resolution for the actual device orientation.

android/src/test/kotlin/dev/steenbakker/mobile_scanner/MobileScannerTest.kt

@@ -0,0 +1,59 @@
+package dev.steenbakker.mobile_scanner
+
+import android.app.Activity
+import android.graphics.Rect
+import androidx.camera.core.ImageProxy
+import com.google.mlkit.vision.barcode.BarcodeScanner
+import com.google.mlkit.vision.barcode.BarcodeScannerOptions
+import com.google.mlkit.vision.barcode.common.Barcode
+import kotlin.test.Test
+import org.mockito.Mockito
+import io.flutter.view.TextureRegistry
+import kotlin.test.expect
+
+/*
+ * This demonstrates a simple unit test of the Kotlin portion of this plugin's implementation.
+ *
+ * Once you have built the plugin's example app, you can run these tests from the command
+ * line by running `./gradlew testDebugUnitTest` in the `example/android/` directory, or
+ * you can run them directly from IDEs that support JUnit such as Android Studio.
+ */
+
+internal class MobileScannerTest {
+    @Test
+    fun isBarcodeInScanWindow_canHandleNaNValues() {
+        val barcodeScannerMock = Mockito.mock(BarcodeScanner::class.java)
+
+        val mobileScanner = MobileScanner(
+            Mockito.mock(Activity::class.java),
+            Mockito.mock(TextureRegistry::class.java),
+            { _: List<Map<String, Any?>>, _: ByteArray?, _: Int?, _: Int? -> },
+            { _: String  -> },
+            { _: BarcodeScannerOptions? -> barcodeScannerMock }
+        )
+
+        // Intentional suppression for the mock value in the test,
+        // since there is no NaN constant.
+        @Suppress("DIVISION_BY_ZERO")
+        val notANumber = 0.0f / 0.0f
+
+        val barcodeMock: Barcode = Mockito.mock(Barcode::class.java)
+        val imageMock: ImageProxy = Mockito.mock(ImageProxy::class.java)
+
+        // TODO: use corner points instead of bounding box
+
+        // Bounding box that is 100 pixels offset from the left and top,
+        // and is 100 pixels in width and height.
+        Mockito.`when`(barcodeMock.boundingBox).thenReturn(
+            Rect(100, 100, 200, 300))
+        Mockito.`when`(imageMock.height).thenReturn(400)
+        Mockito.`when`(imageMock.width).thenReturn(400)
+
+        // Use a scan window that has an invalid value, but otherwise uses the entire image.
+        val scanWindow: List<Float> = listOf(0f, notANumber, 100f, 100f)
+
+        expect(false) {
+            mobileScanner.isBarcodeInScanWindow(scanWindow, barcodeMock, imageMock)
+        }
+    }
+}