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viridite · Joined: 08 Nov 2007 Posts: 16

Hi, guys

recently i'm trying to use SDL's ttf support to make a reader. currently i can use it to display the chinese fonts. but i found a serious problem:

1. i use a cache to read the file first to store some fonts .
2. before every draw of the screen i will then read the char from the buffer and transfer to unicode and then cache the metrics for this screen
3. draw a screen of the fonts.

i found it too slow when switching to another screen because every time i need to cache the metrics and load data from the memory stick. it's too slow!!!

so then i tried to cache all the chinese fonts in memory at the starting time but failed because it will run out of the memory. so i just wonder whether there are some good solutions for this kind of problems??

Thanks!

viridite · Joined: 08 Nov 2007 Posts: 16

why nobody answer this?
did anybody use sdl ttf for development?

J.F. · Joined: 22 Feb 2004 Posts: 2906

Never used it.

You need to wait more than a few hours. Remember that most of the people who would answer your question are professional programmers who just frequent this board in their spare time. You could go a couple days before getting a post.

viridite · Joined: 08 Nov 2007 Posts: 16

thanks!

so you never used ttf to display something? OK.... do you have some interesting things to introduce? haha.

anyway, nice to meet you,kind man!

J.F. · Joined: 22 Feb 2004 Posts: 2906

Nope, never used TTF, but I'm thinking about it. My current GUI code all uses the debug printing, and while it does the job, it's not the prettiest thing. So I'm thinking about switching the display part of the gui to TTF. But that doesn't help you right now. :)

tacoSunday · Joined: 31 Aug 2007 Posts: 34

If you are looking for speed, I would think rendering the ttf once to a bitmap font and then indexing into it with uv coords would be the way to go.

Hmm, just realized you are trying to use Chinese fonts wich would make for a huge bitmap font. I suppose you could use some caching scheme for the rendered chars. I don't know much about chinese writing, but I would assume most writing uses a rather limited subset at any one time.

viridite · Joined: 08 Nov 2007 Posts: 16

tacoSunday · Joined: 31 Aug 2007 Posts: 34

I realize that memory may not be enough. That is why I suggested caching recently used characters instead of the entire character set. This was based on the assumption that only a relatively small subset of them would be in use at any given time. You have a cache of a fixed size (which you tweak to fit in available memory) and when the cache is full and you come across a char that is not already cached render it and and shove it in the cache position of the least recently used char that is cached. I am willing to bet that this will provide acceptable performance .

Best of luck

P.S. I do believe I have set a record for the most uses of the word cache in a single run-on sentence!

viridite · Joined: 08 Nov 2007 Posts: 16

Thanks.

but i think that is not realistic because every try of caching data will cost at least one to two seconds. so once we need to cache some data the user needs to wait two seconds or more , it's not good at least at the very first of the caching process.

but maybe i can try to cache several pages first and then if there are more characters in need i will cache again.....

but in fact i found a famous ereader can finish this without any problem. so i guess there shall be some tricks.

tacoSunday · Joined: 31 Aug 2007 Posts: 34

viridite · Joined: 08 Nov 2007 Posts: 16

Thanks very much...
I tried yesterday and it did speed up... i will try to make it faster by imporving the algorithem. somehow it works fine.

currently i used a cache to load hundreds of charactors and once there appears one that isn't hit in the cache i will replace it with the least used one.

so this method do solved my problem. thanks, everybody.