> @Michalis, does view3dscene work with libpng16, or do you first need to > port view3dscene to that API? If so, we better just drop the dependency > for now.
Hi, I'm not sure what is the dependency ldd detects. It seems that something (possibly some unit inside FPC RTL?) uses the PNG unit (which links to libpng in a traditional way and will be detected like this by ldd). In any case, like Paul writes, view3dscene (actually, Castle Game Engine underneath) loads png library by dlopen/dlsym. This way things work smoothly even when libpng is not available. The loading of libpng library is trivially coded inside CGE in src/images/castlepng_dynamic.inc (we just try to open libpng12.so.0, or libpng.so, or libpng14.so.14...). This probably has to be adjusted to look also for libpng16.so.16, so it will be a 2-line patch to make view3dscene (actually, Castle Game Engine) in Debian work with libpng 1.6. We carefully use a small subset on libpng API that is available in at least libpng 1.2, 1.4. I can test around the weekend whether it also works with libpng 1.6, from briefly reading about libpng 1.5 and 1.6 -- we should be fine. So, the things to do here: 1. Make a 2-line change to CGE to src/images/castlepng_dynamic.inc to try loading libpng16.so.16 . 2. Test whether view3dscene (actually, everything using Castle Game Engine) works with this libpng version. Probably yes:) I'll happily do it in a couple of days, around the nearest weekend:) Sidenotes: - The way we use libpng can be reconfigured to use static linking by defining CASTLE_PNG_STATIC at compilation, see castlepng.pas and castleconf.inc. Although I don't think it's necessary at this point. - In the future CGE and view3dscene releases (which can be tested using our GIT or SVN code right now), by default we use the png loader provided by the FPC fcl-image library. Which uses png reading implemented natively in Pascal in FPC fcl-image. This removes the dependency on libpng entirely. It remains configurable anyway (you can recompile engine with proper options to alternatively use libpng, with traditional linking or with dlopen/dlsym). Regards, Michalis
