selectionClaim seeks to the start of the data before reading it

backends/x/selectionclaim.go

@@ -153,6 +153,7 @@ func (claim *selectionClaim) handleSelectionRequest (
 		if confidence == confidenceNone { die(); return }
 		reader, ok := claim.data[mime]
 		if !ok { die(); return }
+		reader.Seek(0, io.SeekStart)
 		data, err := io.ReadAll(reader)
 		if err != nil { die() }
 		claim.window.fulfillSelectionRequest(data, 32, event)

data/data.go

@@ -5,7 +5,7 @@ import "bytes"
 
 // Data represents arbitrary polymorphic data that can be used for data transfer
 // between applications.
-type Data map[Mime] io.ReadCloser
+type Data map[Mime] io.ReadSeekCloser
 
 // Mime represents a MIME type.
 type Mime struct {