fix(shared): keep dense transfer QR codes scannable

shared/src/commonMain/kotlin/com/vnidrop/app/feature/send/TransferDetails.kt

@@ -37,8 +37,8 @@ import androidx.compose.runtime.remember
 import androidx.compose.runtime.setValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
-import androidx.compose.ui.draw.clip
 import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.graphics.FilterQuality
 import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.text.style.TextOverflow
 import androidx.compose.ui.unit.dp
@@ -59,7 +59,6 @@ import com.vnidrop.app.ui.state.progressForReceiver
 import com.vnidrop.app.ui.theme.LocalVniDropColors
 import org.jetbrains.compose.resources.decodeToImageBitmap
 import org.jetbrains.compose.resources.stringResource
-import qrcode.QRCode
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.withContext
 import vnidrop.shared.generated.resources.*
@@ -247,7 +246,7 @@ internal fun TransferSharePanel(
 		val renderedBitmap by produceState(qrBitmap, ticket, qrBitmap) {
 			if (value == null) {
 				value = withContext(Dispatchers.Default) {
-					runCatching { QRCode.ofSquares().withSize(8).build(ticket).renderToBytes().decodeToImageBitmap() }.getOrNull()
+					runCatching { buildTransferQrCode(ticket).renderToBytes().decodeToImageBitmap() }.getOrNull()
 				}
 				value?.let { onQrRendered(ticket, it) }
 			}
@@ -259,7 +258,12 @@ internal fun TransferSharePanel(
 			color = Color.White,
 		) {
 			if (renderedQr != null) {
-				Image(renderedQr, null, Modifier.padding(14.dp).fillMaxSize().clip(RoundedCornerShape(8.dp)))
+				Image(
+					bitmap = renderedQr,
+					contentDescription = null,
+					modifier = Modifier.padding(14.dp).fillMaxSize(),
+					filterQuality = FilterQuality.None,
+				)
 			} else {
 				Box(Modifier.fillMaxSize(), contentAlignment = Alignment.Center) { CircularProgressIndicator() }
 			}

shared/src/commonMain/kotlin/com/vnidrop/app/feature/send/TransferQrCode.kt

@@ -0,0 +1,29 @@
+package com.vnidrop.app.feature.send
+
+import qrcode.QRCode
+import qrcode.raw.ErrorCorrectionLevel
+
+private const val QrCellSize = 8
+private const val QrQuietZoneModules = 4
+// qrcode-kotlin 4.5.0 falls back to version 40 above version 20's byte capacity.
+private val QrLowErrorCorrectionByteCapacities = intArrayOf(
+	17, 32, 53, 78, 106, 134, 154, 192, 230, 271,
+	321, 367, 425, 458, 520, 586, 644, 718, 792, 858,
+	929, 1003, 1091, 1171, 1273, 1367, 1465, 1528, 1628, 1732,
+	1840, 1952, 2068, 2188, 2303, 2431, 2563, 2699, 2809, 2953,
+)
+
+internal fun buildTransferQrCode(ticket: String): QRCode =
+	QRCode.ofSquares()
+		.withSize(QrCellSize)
+		.withInnerSpacing(0)
+		.withMargin(QrQuietZoneModules * QrCellSize)
+		.withErrorCorrectionLevel(ErrorCorrectionLevel.LOW)
+		.withInformationDensity(transferQrInformationDensity(ticket))
+		.build(ticket)
+
+internal fun transferQrInformationDensity(ticket: String): Int {
+	val byteCount = ticket.encodeToByteArray().size
+	val index = QrLowErrorCorrectionByteCapacities.indexOfFirst { byteCount <= it }
+	return if (index >= 0) index + 1 else throw IllegalArgumentException("The invitation is too large for a QR code")
+}

shared/src/commonTest/kotlin/com/vnidrop/app/feature/send/TransferQrCodeTest.kt

@@ -0,0 +1,22 @@
+package com.vnidrop.app.feature.send
+
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+class TransferQrCodeTest {
+	@Test
+	fun ticketPastVersionTwentyCapacityUsesNextAvailableVersion() {
+		assertEquals(20, transferQrInformationDensity("a".repeat(858)))
+		assertEquals(21, transferQrInformationDensity("a".repeat(859)))
+		assertEquals(21, transferQrInformationDensity("a".repeat(876)))
+	}
+
+	@Test
+	fun renderedQrUsesExpectedVersionSizeAndQuietZone() {
+		val qrCode = buildTransferQrCode("a".repeat(876))
+
+		assertEquals(21, qrCode.informationDensity)
+		assertEquals(101, qrCode.rawData.size)
+		assertEquals(872, qrCode.canvasSize)
+	}
+}