i know that but if a character is not cannon as `straight` or `gay` is there something wrong with fans who draw them being gay or not?
Not at all. They should acknowledge, though, that the character has more of a chance of being straight.
my quistion is how can you see/view a character being gay or not? does a character have to be partnerd up with the same sex be a crossdresser act like a typcail steoryo type homosexual like you see on tv have female intress? does the character must mention his own sexualty in a movie/series/comic to be `Gay cannon`?
In order to be canon? Yes, he must show it, or the writer/director must say it. But the same applies to heterosexual characters. The difference being that a heterosexual will usually be portrayed as such somewhere, even if it's something minor, whereas characters who are possibly gay have a reduced chance of being portrayed as such, unless it's a plot point.