Share a card's image from the preview

A share button beside the preview's close button sends the face being
shown at Scryfall's large size: on desktop the image is decoded and put on
the clipboard (tauri-plugin-clipboard-manager); on Android it's saved to
the cache and handed to the system share sheet by a small in-repo plugin
(SharePlugin.kt) through the app's FileProvider. The preview's corner
buttons are also a little larger.

src-tauri/gen/android/app/src/main/java/com/garrettmills/mtgc/SharePlugin.kt

@@ -0,0 +1,51 @@
+package com.garrettmills.mtgc
+
+import android.app.Activity
+import android.content.ClipData
+import android.content.Intent
+import androidx.core.content.FileProvider
+import app.tauri.annotation.Command
+import app.tauri.annotation.InvokeArg
+import app.tauri.annotation.TauriPlugin
+import app.tauri.plugin.Invoke
+import app.tauri.plugin.Plugin
+import java.io.File
+
+@InvokeArg
+class ShareImageArgs {
+  /** A JPEG under the app's cache dir, which the FileProvider exposes. */
+  lateinit var path: String
+  var title: String? = null
+}
+
+/**
+ * The Android half of the app's `share` plugin (src-tauri/src/share.rs):
+ * opens the system share sheet for a card image the Rust side has saved.
+ */
+@TauriPlugin
+class SharePlugin(private val activity: Activity) : Plugin(activity) {
+  @Command
+  fun shareImage(invoke: Invoke) {
+    try {
+      val args = invoke.parseArgs(ShareImageArgs::class.java)
+      val uri = FileProvider.getUriForFile(
+        activity,
+        "${activity.packageName}.fileprovider",
+        File(args.path),
+      )
+      val send = Intent(Intent.ACTION_SEND).apply {
+        type = "image/jpeg"
+        putExtra(Intent.EXTRA_STREAM, uri)
+        args.title?.let { putExtra(Intent.EXTRA_TITLE, it) }
+        // ClipData lets the chooser show a preview of the image, and carries
+        // the read grant along with it.
+        clipData = ClipData.newRawUri(args.title, uri)
+        addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION)
+      }
+      activity.startActivity(Intent.createChooser(send, args.title))
+      invoke.resolve()
+    } catch (ex: Exception) {
+      invoke.reject(ex.message)
+    }
+  }
+}