又係GRAMMAR.......>_<

I'm happy to see... - I look forward to seeing...

I'm happy seeing... - I'm happy when I see...

Example:
1. I am happy to see a nice movie. [One possibility: glad I've bought tickets to it. ]

2. I am happy seeing a nice movie. [More about: excited/happy while seeing the movie.]

Therefore,

I am happy to see the woman knocked down by the lorry.
我會開心見到個女人俾車撞


I am happy to see you are coming - someone really arrived
I am happy to see you coming - wishing someone to come

**********************
Good Luck

I am happy to see the woman knocked down by the lorry
系解我見到個女人俾車撞 好開心

因爲系話I am happy吖


I am happy to see you are coming----系：我見到你黎緊好開心，姐系話你系知道 佢會黎，同埋系you are coming,所以系present continuous tense,姐系話個個人系coming.

I am happy tp see you coming----系：我期待能見到你來。I am looking foward/ hope to see you soon.同埋前面冇are,所以唔系present continuous tense


希望幫到你