method zoom () =
let z =
try Scanf.sscanf wcombo#entry#text "%d%%" (fun a -> Some a)
with _ -> None
in
match z with
None -> ()
| Some 100 ->
current_zoom <- 100.0;
image#set_file png_file
| Some z ->
let f = self#zoom_file_of_zoom z in
if Sys.file_exists f then
image#set_file f
else
show image png_file f z;
current_zoom <- float z