replace libpng with libspng

[shuffle2]

This only replaces the png library dolphin itself uses (mgba and Qt use their own).
It also allows getting rid of the gross C support code needed for libpng and make the External a submodule.

oof, i had a bug that made me think the speedup was a lot more than it really is. There is about 10% speedup for smaller png writes, for larger ones it's actually a bit slower (but still faster overall than current master, thanks to zlib-ng).

On the read path, I tested by comparing time taken for prefetching the hypatia wind waker hires texture set to load:
this PR: 66 seconds
zlib-ng branch: 95 seconds
master (zlib and libpng): 130 seconds

Not sure how to make it work with cmake.

[AdmiralCurtiss]

The reason you can't get CMake to work is because spng's CMakeLists.txt does not set any include directory on the spng/spng_static target. So they don't get set when linking to it. It also unconditionally installs the spng headers, which we probably don't want.

Since its compilation steps are very simple I think we can just make a custom replacement for it instead of trying to make it behave. Replace the entirety of our spng CMakeLists.txt (the one outside the submodule) with:

cmake_minimum_required(VERSION 3.0)

project(spng C)

add_library(spng STATIC ${CMAKE_CURRENT_LIST_DIR}/libspng/spng/spng.c)
target_compile_definitions(spng PUBLIC SPNG_STATIC)
target_link_libraries(spng PUBLIC ZLIB::ZLIB)
target_include_directories(spng PUBLIC ${CMAKE_CURRENT_LIST_DIR}/libspng/spng/)
dolphin_disable_warnings_msvc(spng)

[shuffle2]

Thanks!

[iwubcode]

Code wise this LGTM (just looked at the png changes). I tested Dynamic Input Textures, loading a texture pack, and dumping some textures. All seemed to work fine

[dolphin-emu-bot]

FifoCI detected that this change impacts graphical rendering. Here are the behavior differences detected by the system:

• aeon-charge-attack on ogl-lin-radeon: diff
• chibi-robo-fastdepth on ogl-lin-radeon: diff
• chibi-robo-zfighting on ogl-lin-radeon: diff
• dbz-depth on ogl-lin-radeon: diff
• djfny-menu on ogl-lin-radeon: diff
• DKCR-Char on ogl-lin-radeon: diff
• ea-vp6 on ogl-lin-radeon: diff
• find-mii on ogl-lin-radeon: diff
• fog-adj on ogl-lin-radeon: diff
• fortune-street on ogl-lin-radeon: diff
• fortune-street-fog on ogl-lin-radeon: diff
• fortune-street-white-box on ogl-lin-radeon: diff
• fsa-layers on ogl-lin-radeon: diff
• inverted-depth-range on ogl-lin-radeon: diff
• kirby-shadows on ogl-lin-radeon: diff
• line-width-test on ogl-lin-radeon: diff
• luigi-shadows on ogl-lin-radeon: diff
• mario-sluggers-bar on ogl-lin-radeon: diff
• mario-tennis-menu on ogl-lin-radeon: diff
• megaman-heat on ogl-lin-radeon: diff
• melee-lighting on ogl-lin-radeon: diff
• mii-channel on ogl-lin-radeon: diff
• milotic-texture on ogl-lin-radeon: diff
• mini-ninjas on ogl-lin-radeon: diff
• mkdd-efb on ogl-lin-radeon: diff
• mkwii-bluebox on ogl-lin-radeon: diff
• monkeyball-fuse on ogl-lin-radeon: diff
• mp7-text on ogl-lin-radeon: diff
• mtennis-zfreeze on ogl-lin-radeon: diff
• my-word-coach on ogl-lin-radeon: diff
• nddemo-bumpmapping on ogl-lin-radeon: diff
• nfsu-purplerect on ogl-lin-radeon: diff
• nfsu-reflections on ogl-lin-radeon: diff
• nsmbw-coins on ogl-lin-radeon: diff
• nsmbw-intro on ogl-lin-radeon: diff
• pm-hc-jp on ogl-lin-radeon: diff
• puzzle-collection on ogl-lin-radeon: diff
• pw-black-bars on ogl-lin-radeon: diff
• rs2-glass on ogl-lin-radeon: diff
• rs2-skybox on ogl-lin-radeon: diff
• rs2-zfreeze on ogl-lin-radeon: diff
• sadx-ui on ogl-lin-radeon: diff
• sf-assault-flashing on ogl-lin-radeon: diff
• smg2-fog on ogl-lin-radeon: diff
• smg-marioeyes on ogl-lin-radeon: diff
• sms-bubbles on ogl-lin-radeon: diff
• sms-gc on ogl-lin-radeon: diff
• soa-black on ogl-lin-radeon: diff
• soniccolors-mm on ogl-lin-radeon: diff
• sonicriderszg-gb on ogl-lin-radeon: diff
• spyro-bloom on ogl-lin-radeon: diff
• ssbm-pointsize on ogl-lin-radeon: diff
• ss-map on ogl-lin-radeon: diff
• super-sluggers-white-out on ogl-lin-radeon: diff
• thps4-shadow on ogl-lin-radeon: diff
• tos-invis-char on ogl-lin-radeon: diff
• tsp3-pinkgrass on ogl-lin-radeon: diff
• xenoblade-menu on ogl-lin-radeon: diff
• zelda1-vc on ogl-lin-radeon: diff
• ztp-grass on ogl-lin-radeon: diff
• zww-armos on ogl-lin-radeon: diff
• zww-water on ogl-lin-radeon: diff
• zww-waves on ogl-lin-radeon: diff

_{^{automated-fifoci-reporter}}

[shuffle2]

i don't think this PR should have made fifoci complain, nor the zlib-ng change, so idk what's up with that :(

[dvessel]

Texture dumps can’t be read by anything using libpng. This looks like a bug with libspng.

❯ pngquant --verbose tex1_128x128_m_114e37a06b3ef23b_14_arb-bad.png
tex1_128x128_m_114e37a06b3ef23b_14_arb-bad.png:
  error: Read error (libpng failed)
  error: cannot decode image tex1_128x128_m_114e37a06b3ef23b_14_arb-bad.png
There were errors quantizing 1 file out of a total of 1 file.

❯ identify -verbose tex1_128x128_m_114e37a06b3ef23b_14_arb-bad.png
identify: Expected 8 bytes; found 0 bytes `tex1_128x128_m_114e37a06b3ef23b_14_arb-bad.png' @ warning/png.c/MagickPNGWarningHandler/1750.
identify: Read Exception `tex1_128x128_m_114e37a06b3ef23b_14_arb-bad.png' @ error/png.c/MagickPNGErrorHandler/1716.

example files:

[shuffle2]

a bug with libspng or with libpng 🤔 they seem like valid pngs to software on my system (and also github/browser, which displays them fine...)

[dvessel]

Not sure but I filed a bug with libspng. All my gui apps reads them just fine but if some command line tool uses libpng, it will fail.

randy408/libspng#226

[shuffle2]

@dvessel actually i took a look using the pngcheck tool of libpng and think this will fix it, can you check: #10907

[Rumi-Larry]

Since this PR was made the file at "dolphin/Source/PCH/nopch/pch.h" is no longer necessary.