Improve doc strings for file dialogs

dialog/file.go

@@ -831,33 +831,40 @@ func (f *FileDialog) SetView(v ViewLayout) {
 }
 
 // NewFileOpen creates a file dialog allowing the user to choose a file to open.
-// The callback function will run when the dialog closes. The URI will be nil
-// when the user cancels or when nothing is selected.
+//
+// The callback function will run when the dialog closes and provide a reader for the chosen file.
+// The reader must be closed by the callback.
+// The reader will be nil, when the user cancels or when nothing is selected.
 //
 // The dialog will appear over the window specified when Show() is called.
-func NewFileOpen(callback func(fyne.URIReadCloser, error), parent fyne.Window) *FileDialog {
+func NewFileOpen(callback func(reader fyne.URIReadCloser, err error), parent fyne.Window) *FileDialog {
 	dialog := &FileDialog{callback: callback, parent: parent}
 	return dialog
 }
 
 // NewFileSave creates a file dialog allowing the user to choose a file to save
 // to (new or overwrite). If the user chooses an existing file they will be
-// asked if they are sure. The callback function will run when the dialog
-// closes. The URI will be nil when the user cancels or when nothing is
-// selected.
+// asked if they are sure.
+//
+// The callback function will run when the dialog closes and provide a writer for the chosen file.
+// The writer must be closed by the callback.
+// The writer will be nil, when the user cancels or when nothing is selected.
 //
 // The dialog will appear over the window specified when Show() is called.
-func NewFileSave(callback func(fyne.URIWriteCloser, error), parent fyne.Window) *FileDialog {
+func NewFileSave(callback func(writer fyne.URIWriteCloser, err error), parent fyne.Window) *FileDialog {
 	dialog := &FileDialog{callback: callback, parent: parent, save: true}
 	return dialog
 }
 
 // ShowFileOpen creates and shows a file dialog allowing the user to choose a
-// file to open. The callback function will run when the dialog closes. The URI
-// will be nil when the user cancels or when nothing is selected.
+// file to open.
+//
+// The callback function will run when the dialog closes and provide a reader for the chosen file.
+// The reader must be closed by the callback.
+// The reader will be nil, when the user cancels or when nothing is selected.
 //
 // The dialog will appear over the window specified.
-func ShowFileOpen(callback func(fyne.URIReadCloser, error), parent fyne.Window) {
+func ShowFileOpen(callback func(reader fyne.URIReadCloser, err error), parent fyne.Window) {
 	dialog := NewFileOpen(callback, parent)
 	if fileOpenOSOverride(dialog) {
 		return
@@ -867,12 +874,14 @@ func ShowFileOpen(callback func(fyne.URIReadCloser, error), parent fyne.Window)
 
 // ShowFileSave creates and shows a file dialog allowing the user to choose a
 // file to save to (new or overwrite). If the user chooses an existing file they
-// will be asked if they are sure. The callback function will run when the
-// dialog closes. The URI will be nil when the user cancels or when nothing is
-// selected.
+// will be asked if they are sure.
+//
+// The callback function will run when the dialog closes and provide a writer for the chosen file.
+// The writer must be closed by the callback.
+// The writer will be nil, when the user cancels or when nothing is selected.
 //
 // The dialog will appear over the window specified.
-func ShowFileSave(callback func(fyne.URIWriteCloser, error), parent fyne.Window) {
+func ShowFileSave(callback func(writer fyne.URIWriteCloser, err error), parent fyne.Window) {
 	dialog := NewFileSave(callback, parent)
 	if fileSaveOSOverride(dialog) {
 		return