Getting SDL to work on DirectFB

[B_Lizzard]

So, I've gotten SDL compiled using DirectFB as a backend. SDL_ttf has some issue with TTF_OpenFont so I can't run nethack-newt, but fheroes2 only requires SDL and SDL_image, and seems to run well.

My problem is, I can't get anything to display on the screen. The game starts up, but the Kindle display only shows some brief garbled images here and there. I have DirectFB configured with what Amazon uses in /opt/amazon/ebook/config/wrs.ini. I've tried other configuration options but nothing seems to do the trick. I've also tried to run the game with /etc/init.d/framework stopped. No cigar.

Does anyone with more experience have any idea how to make this work? I don't really know how DirectFB works, so any help would be more than welcome.

EDIT: Of course, SDL over the normal Linux framebuffer was my original choice, but it can't be done because the fbcon driver for SDL needs VT support in the kernel.

[hawhill]

I think the VT-related bits only make a really small portion of the code -- most probably just for switching to a new VT upon initialization and switching back when finishing. You should be able to easily strip this dependency from SDL.

Are you sure that using DirectFB will care for driving the eink display? Most probably it doesn't and you need to communicate the dirty regions to the eink driver yourself, just as you would when using the raw framebuffer...

[B_Lizzard]

Ah, I thought such logic would be built in the fbdev driver for DirectFB which included in the Kindle firmware. I'll need to look into how Amazon does it with webkit.

I'll also have to look into running Xfbdev or something, this low-level stuff isn't making my life any easier.

[mark03]

Hey b_lizzard (and others),

Were you able to make any headway on this? I'm not so much interested in SDL, but I would like to understand how the Amazon Framework is using directfb and what communication channel they are using to trigger eink refreshes via the eink hal. In other words, is it user apps triggering those refreshes, working around the rest of the directfb stuff, or does their directfb have some kind of logic to automatically do this?

In my simplistic view of the world it seems like a lot of GTK+ apps could be built for Kindle, on top of directfb.

[h1uke]

Originally Posted by mark03

what communication channel they are using to trigger eink refreshes via the eink hal.

for example:

echo 2 >/proc/eink_fb/update_display

performs full screen update.
Have a look at attached file for more.

HTH

[mark03]

Hi h1uke,

I know you *can* refresh the display using the /proc interface. There are also ioctls that can be called to do the same thing.

My question, though, was not "does anyone know how to make the screen refresh" but rather, how the Amazon Framework is going about it. And in particular, have they modified their version of directfb to accomplish this? Or are they working around directfb, having the app trigger refreshes directly via /proc or ioctls?

Since they already have directfb on the system, and there are a ton of apps that could run under directfb (thanks to directfb-gtk support), this seems like a promising avenue of research...

[B_Lizzard]

The version of SDL I compiled used the DirectFB libs shipping with the Kindle, so no. I am guessing the screen update logic goes into each toolkit, and that directfb-gtk (which, I'm guessing, is what the web-browser is using) has been patched. Or webkit itself.

I did not know of einkfb. I'll look into it and patch SDL. Maybe then we can have nethack.

[mark03]

Diffing Amazon's directfb-1.2.0 against the version from directfb.org is quite interesting. Probably more instructive for someone who's actually used these libraries before They've added a "SetDirtyRectangle" call to the API. I haven't looked at this long enough to see how it works though.

Their GTK+ had more extensive patches. There's a bunch of stuff in "gdk marshaling" that sailed way over my head, but I wonder if it has to do with batching up things between eink display updates?

For my bicycle-computer app I intend to work at the directfb level and trigger updates manually via the ioctls if I can't figure out the dirty-rectangle stuff.

[twobob]

Did this ever get done. I was thinking of pursuing aalib support...

Cheers.

[twobob]

anyone. anything further on this?

[geekmaster]

Originally Posted by twobob

anyone. anything further on this?

I am sure that there are LOTS of people who would be interested in WATCHING you do this. This IS a "spectator sport" isn't it? You know, like the "Kindle Developer's Channel" on cable TV?

Actually, we need more DEVELOPERS in the Developer's Corner.

And yes, I want SDL. Not enough time in a day (or a lifetime) to do all I want...

[twobob]

I'm digging around best I can.

It is probably a few screen to eink calls away from working

[B_Lizzard]

I did manage a few more tests but nothing conclusive. SDL will need to be patched for it to work, and I didn't find any time to do so, sorry.

[twobob]

no worries. I got it working for the 5 in the end. (posted)
http://www.mobileread.com/forums/sho...9&postcount=65
and
http://www.mobileread.com/forums/sho...9&postcount=66

and built for the 3. (needs 4bpp FB tweaks to be useful or aalib support which I have)

Thanks mate!