A funny thing happened while refactoring the function argument parsing
in the `PNGGenConfig` module: the processing of dependencies inside
the CMake function `generate_copy` got fixed, thanks to an inadvertent
typo correction!
Going down the rabbit hole, we uncovered two issues:
1. A typo in `scripts/cmake/PNGGenConfig.cmake` caused a dependency
declaration to disappear, disrupting the graph. Fortunately, this
disruption was being mitigated by an additional set of (redundant)
symbolic target declarations that kept the CMake build going.
2. The exact string matching inside `scripts/cmake/gensrc.cmake.in`
imposed an artificial limitation, disallowing the use of absolute
file paths.
The typo correction in (1), and the use of regex matching instead of
exact string matching in (2), allowed us to use absolute file paths
in the main CMake file, consistently, thus allowing CMake to recognize
them as uniquely-identifiable nodes in the dependency graph. There
should be no further need to have extra symbolic targets for proper
node identification.
In the end, we shaved off the redundant symbolic target declarations,
retaining only `png_genfiles` and `png_genprebuilt`.
From the libpng licensing point of view, the build projects, the build
scripts, the test scripts, the CI verification scripts, et cetera, have
not traditionally been part of libpng proper, although some of these,
including the CMake-based build, have been released under the libpng
license.
Considering how the CMake build grew as a result of many contributions
from many contributing authors over a long time, one may argue that it
almost became an individual piece of software in its own right.
Moving on, everything CMake-related shall be placed in the subdirectory
scripts/cmake/ (except, of course, the main CMakeLists.txt). Moreover,
contributing authors shall be acknowledged in scripts/cmake/AUTHORS.md.
Please see scripts/cmake/README.md for more information.
