[mob][photos] Fix share outside of ente not working at multiple places on iPad

For the ios share sheet to be shown properly on iPad, the position of the button that triggered it needs to be known, which requires BuildContext and GlobalKey of the button, which is difficult to pass from some parts of code. So to make it work, we pass a default point on the screen so that the share sheet at least shows up

mobile/lib/ui/viewer/actions/file_selection_actions_widget.dart

@@ -777,7 +777,12 @@ class _FileSelectionActionsWidgetState
       final String url =
           "${_cachedCollectionForSharedLink!.publicURLs?.first?.url}#$collectionKey";
       unawaited(Clipboard.setData(ClipboardData(text: url)));
-      await shareImageAndUrl(placeholderPath!, url, context, sendLinkButtonKey);
+      await shareImageAndUrl(
+        placeholderPath!,
+        url,
+        context: context,
+        key: sendLinkButtonKey,
+      );
       if (placeholderPath != null) {
         final file = File(placeholderPath!);
         try {

mobile/lib/utils/share_util.dart

@@ -72,8 +72,10 @@ Future<void> share(
   }
 }
 
+/// Returns the rect of button if context and key are not null
+/// If key is null, returned rect will be at the center of the screen
 Rect shareButtonRect(BuildContext context, GlobalKey? shareButtonKey) {
-  Size size = MediaQuery.of(context).size;
+  Size size = MediaQuery.sizeOf(context);
   final RenderObject? renderObject =
       shareButtonKey?.currentContext?.findRenderObject();
   RenderBox? renderBox;
@@ -92,8 +94,21 @@ Rect shareButtonRect(BuildContext context, GlobalKey? shareButtonKey) {
   );
 }
 
-Future<ShareResult> shareText(String text) async {
-  return Share.share(text);
+Future<ShareResult> shareText(
+  String text, {
+  BuildContext? context,
+  GlobalKey? key,
+}) async {
+  try {
+    final sharePosOrigin = _sharePosOrigin(context, key);
+    return Share.share(
+      text,
+      sharePositionOrigin: sharePosOrigin,
+    );
+  } catch (e, s) {
+    _logger.severe("failed to share text", e, s);
+    return ShareResult.unavailable;
+  }
 }
 
 Future<List<EnteFile>> convertIncomingSharedMediaToFile(
@@ -214,13 +229,29 @@ void shareSelected(
 
 Future<void> shareImageAndUrl(
   String imagePath,
-  String url,
-  BuildContext context,
-  GlobalKey key,
-) async {
+  String url, {
+  BuildContext? context,
+  GlobalKey? key,
+}) async {
+  final sharePosOrigin = _sharePosOrigin(context, key);
+
   await Share.shareXFiles(
     [XFile(imagePath)],
     text: url,
-    sharePositionOrigin: shareButtonRect(context, key),
+    sharePositionOrigin: sharePosOrigin,
   );
 }
+
+/// required for ipad https://github.com/flutter/flutter/issues/47220#issuecomment-608453383
+/// This returns the position of the share button if context and key are not null
+/// and if not, it returns a default position so that the share sheet on iPad has
+/// some position to show up.
+Rect _sharePosOrigin(BuildContext? context, GlobalKey? key) {
+  late final Rect rect;
+  if (context != null) {
+    rect = shareButtonRect(context, key);
+  } else {
+    rect = const Offset(20.0, 20.0) & const Size(10, 10);
+  }
+  return rect;
+}