The function to do the work scanned the full list of drawsegs to find portals, which with a large amount of masked geometry and/or drawsegs could become extremely slow.
Changed it so that R_DrawMasked collects all portal related drawsegs up front so that the actual clipping code can
a) scan a far shorter list and
b) can skip half of the validation.
Also using P_PointOnLinePrecise to shave off a small bit of additional time.
The reason is that in such a case it is very likely that the IWAD defines its own menu and will most likely not provide all assets for the base definitions. See 'Adventures of Square' for an example.
Attempts to output errors with bad characters encountered during text lumps parsing were failed miserably because of UTF-8 conversion
Example: loading of GZ-Models-r16.pk3 with GZDoom caused 'NSConcreteAttributedString initWithString:: nil value' exception
During loading of .pk3 that stores hundred of .wad's significant amount of time were spent on scrolling text to the last line
The same applies to other cases like output of thousands warnings/errors
* Arch-Vile resurrection
* Boom point pushers (due to complete lack of z-handling only for line portals.)
* A_RadiusGive
These also require a more thorough collection of portal groups than simple position checks.
It can easily happen that the lower sector has no lines below the checked area, in which case it would not set the dropoffz correctly. To prevent this, P_LineOpening must, when it checks the opening over a sector portal, actually calculate the dropoff to the lower portal itself by calling sector_t::NextLowestPointAt. It also means that FindRefPoint must calculate a proper reference point when one side of the line to be checked is part of a floor portal.
This fixes Clang complaining about unknown command option '-Wno-unused-but-set-variable' when compiling dumb.
Also I got no new warnings on Clang by excluding '-Wno-unused-result'.
This includes:
* allow one sided portal linedefs to be crossable when part of a polyobject. Due to the limitations, two-sided linedefs won't work here. For general use this is still not allowed because making them passable would require some crippling fudging.
* delay portal finalization until after polyobjects have been spawned.
* the camera interpolation also needs to handle angle differences.
The code is still not 100% complete - the most important thing that is still missing is proper handling of P_CheckPosition through arbitrary portals.
- added portal offsetting to all AproxDistance, AngleTo and Vec*To members of AActor.
- optimized displacement retrieval so that the most common case with no offset retrieves a constant null-vector which can be optimized away fully by the compiler.
- early out in P_GetOffsetPosition if there's no portal lines nearby, so that the common case can skip the traverser completely even on maps with line portals.
