Last year, however, Xue finally secured backing from Hong Kong film mogul Bill Kong Chi-keung, and Ocean Heaven was made with a stellar cast and crew she had not thought possible.

Martial arts star Jet Li - who was impressed enough by the story to work free of charge - appears in his first non-action role as the father, an ailing aquarium mechanic. Wen Chang, who shot to fame last year in the mainland television series Dwelling Narrowness, plays his autistic son.

Japanese composer Joe Hisaishi - well-known for his work for master animator Hayao Miyazaki - was recruited to write the musical score, joining a team that also included editor William Chang Suk-ping, production designer Yee Chung-man and cinematographer Christopher Doyle.

Making its debut this month at the Shanghai Film Festival, Ocean Heaven won the Best Film, Best Director and Best Actor (for Wen) titles for Chinese-language entries.

Such accolades, however, don't seem to figure in Xue's main concerns. 'The major challenge is getting experts to acknowledge that we haven't presented audiences with a distorted view of what autism is - this is perhaps the most important part of my job,' she says.

She attributes Ocean Heaven's impact to Wen's preparation for his role. She asked him to spend several months in close contact with autistic people and had him watch documentaries about the condition. Xue has been volunteering at an NGO for autistic children since the mid-1990s. A graduate student at the film academy at the time, she read a magazine article about their work and offered her help.

'Of course, I wasn't thinking of making film about [autistic people] then. It was just very simple - I want to see whether I could do something for them.'

It was only after the death of a young autistic man she had known for years that Xue began to develop Ocean Heaven, encouraged also by the success of screenplays about family, including the one she co-wrote with Chen Kaige, Together, about a man's efforts to nurture the abilities of his musical prodigy son.

'The [autistic] children I knew had all grown up by then, and their parents were all in their 60s. I was thinking how they would cope when their closest relatives were all gone,' Xue says.

The idea inspired her to write a story about a cancer-stricken man's attempts to prepare his autistic son for a future without his care.

Ocean Heaven begins with Wang Xincheng (Li) trying to end his troubles by drowning his son Dafu (Wen) and then himself. When that fails, Wang begins scouring for an institution that can look after Dafu when he dies. Fortunately, he encounters goodness at nearly every turn, instead of indifference or hostility from the state.

Yet Xue admits the authorities could do more on social welfare, having seen how private groups struggle to maintain services for the disabled.

'It's not something I wanted to explore in this film - but you can see the situation from the film's depiction of how these self-financed care centres operate on very limited resources,' she says. 'I believe everyone has a good heart - but not everyone has the ability to follow through on their good intentions.'

Xue hopes the film will alter public perceptions about autism and put such issues as care for the disabled on the national agenda.

'Life remains a challenge for the 83 million disabled people trying to live within the public welfare framework,' she says. 'And it's possible that a lot of people know about them, but don't care that much. This film is for them.'

Nevertheless, she says Ocean Heaven isn't a lecture dressed up as movie. 'Films like this work because of their characters, story and whether they are emotionally engaging,' she says. 'It's not a propaganda tool ... my primary aim is to produce an entertaining movie. I don't want viewers to go in thinking they are to be taught something. Rather, it's about using the story to cultivate sympathy and understanding.'

In the wrong hands, a story like Ocean Heaven could have turned into an overbearing melodrama, and that's why Xue insisted on directing it herself.

'I never thought about becoming a director before - a screenwriter's life is nice enough,' she says. 'But with this particular subject, I was worried that other directors may not properly understand what the story entails. At least I will be more precise in the details here.'

Just as Ocean Heaven has turned into a wildly different film from what it set out to be, her career aspirations have changed somewhat since she wrote the screenplay. She has already started to make her second film. Titled Running Girl, it is the story of a Guangxi village girl who becomes one of China's top distance runners but then gives up her opportunity for medal greatness to fulfil the national coach's strategy at an international race.

The film is being produced by actress-singer Karen Mok Man-wai, who will also play the lead role. Combining a feel-good, patriotic story with star power - and riding on the success of Ocean Heaven - Xue's days of pitching to indifferent investors are probably over.

Ocean Heaven opens today