Add experimental MPV player backend (#161)

Experimental MPV player backend

Related to #14, #22, & #85

You can switch to MPV in advanced settings and toggle using hardware
decoding or not.

This uses code and buildscripts from
https://github.com/mpv-android/mpv-android, plus other third party
libraries to build MPV

scripts/mpv/include/ci.sh

@@ -0,0 +1,91 @@
+#!/bin/bash -e
+
+# go to buildscripts root folder
+cd "$( dirname "${BASH_SOURCE[0]}" )/.."
+
+. ./include/depinfo.sh
+
+msg() {
+	printf '==> %s\n' "$1"
+}
+
+fetch_prefix() {
+	if [[ "$CACHE_MODE" == folder ]]; then
+		local text=
+		if [ -f "$CACHE_FOLDER/id.txt" ]; then
+			text=$(cat "$CACHE_FOLDER/id.txt")
+		else
+			echo "Cache seems to be empty"
+		fi
+		printf 'Expecting "%s",\nfound     "%s".\n' "$ci_tarball" "$text"
+		if [[ "$text" == "$ci_tarball" ]]; then
+			tar -xzf "$CACHE_FOLDER/data.tgz" -C prefix && return 0
+		fi
+	fi
+	return 1
+}
+
+build_prefix() {
+	msg "Building the prefix ($ci_tarball)..."
+
+	msg "Fetching deps"
+	IN_CI=1 ./include/download-deps.sh
+
+	# build everything mpv depends on (but not mpv itself)
+	for x in ${dep_mpv[@]}; do
+		msg "Building $x"
+		./buildall.sh $x
+	done
+
+	if [[ "$CACHE_MODE" == folder && -w "$CACHE_FOLDER" ]]; then
+		msg "Compressing the prefix"
+		tar -cvzf "$CACHE_FOLDER/data.tgz" -C prefix .
+		echo "$ci_tarball" >"$CACHE_FOLDER/id.txt"
+	fi
+}
+
+export WGET="wget --progress=bar:force"
+
+if [ "$1" = "export" ]; then
+	# export variable with unique cache identifier
+	echo "CACHE_IDENTIFIER=$ci_tarball"
+	exit 0
+elif [ "$1" = "install" ]; then
+	# install deps
+	if [[ -n "$ANDROID_HOME" && -d "$ANDROID_HOME" ]]; then
+		msg "Linking existing SDK"
+		mkdir -p sdk
+		ln -sv "$ANDROID_HOME" sdk/android-sdk-linux
+	fi
+
+	msg "Fetching SDK + NDK"
+	IN_CI=1 ./include/download-sdk.sh
+
+	msg "Fetching mpv"
+	mkdir -p deps/mpv
+	$WGET https://github.com/mpv-player/mpv/archive/master.tar.gz -O master.tgz
+	tar -xzf master.tgz -C deps/mpv --strip-components=1
+	rm master.tgz
+
+	msg "Trying to fetch existing prefix"
+	mkdir -p prefix
+	fetch_prefix || build_prefix
+	exit 0
+elif [ "$1" = "build" ]; then
+	# run build
+	:
+else
+	exit 1
+fi
+
+msg "Building mpv"
+./buildall.sh -n mpv || {
+	# show logfile if configure failed
+	[ ! -f deps/mpv/_build/config.h ] && cat deps/mpv/_build/meson-logs/meson-log.txt
+	exit 1
+}
+
+msg "Building mpv-android"
+./buildall.sh -n
+
+exit 0

scripts/mpv/include/depinfo.sh

@@ -0,0 +1,43 @@
+#!/bin/bash -e
+
+## Dependency versions
+# Make sure to keep v_ndk and v_ndk_n in sync, both are listed on the NDK download page
+
+v_sdk=11076708_latest
+v_ndk=r29
+v_ndk_n=29.0.14206865
+v_sdk_platform=35
+v_sdk_build_tools=35.0.0
+
+v_lua=5.2.4
+v_unibreak=6.1
+v_harfbuzz=12.1.0
+v_fribidi=1.0.16
+v_freetype=2.14.1
+v_mbedtls=3.6.4
+
+
+## Dependency tree
+# I would've used a dict but putting arrays in a dict is not a thing
+
+dep_mbedtls=()
+dep_dav1d=()
+dep_ffmpeg=(mbedtls dav1d)
+dep_freetype2=()
+dep_fribidi=()
+dep_harfbuzz=()
+dep_unibreak=()
+dep_libass=(freetype2 fribidi harfbuzz unibreak)
+dep_lua=()
+dep_libplacebo=()
+dep_mpv=(ffmpeg libass lua libplacebo)
+dep_mpv_android=(mpv)
+
+
+## for CI workflow
+
+# pinned ffmpeg revision
+v_ci_ffmpeg=n8.0
+
+# filename used to uniquely identify a build prefix
+ci_tarball="prefix-ndk-${v_ndk}-lua-${v_lua}-unibreak-${v_unibreak}-harfbuzz-${v_harfbuzz}-fribidi-${v_fribidi}-freetype-${v_freetype}-mbedtls-${v_mbedtls}-ffmpeg-${v_ci_ffmpeg}.tgz"

scripts/mpv/include/path.sh

@@ -0,0 +1,32 @@
+#!/bin/bash
+
+DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && cd .. && pwd )"
+
+. "$DIR/include/depinfo.sh"
+
+os=linux
+[[ "$OSTYPE" == "darwin"* ]] && os=mac
+export os
+
+if [ "$os" == "mac" ]; then
+	[ -z "$cores" ] && cores=$(sysctl -n hw.ncpu)
+	# various things rely on GNU behaviour
+	export INSTALL=`which ginstall`
+	export SED=gsed
+else
+	[ -z "$cores" ] && cores=$(grep -c ^processor /proc/cpuinfo)
+fi
+cores=${cores:-4}
+
+# configure pkg-config paths if inside buildscripts
+if [ -n "$ndk_triple" ]; then
+	export PKG_CONFIG_SYSROOT_DIR="$prefix_dir"
+	export PKG_CONFIG_LIBDIR="$PKG_CONFIG_SYSROOT_DIR/lib/pkgconfig"
+	unset PKG_CONFIG_PATH
+fi
+
+toolchain=$(echo "$DIR/sdk/android-ndk-${v_ndk}/toolchains/llvm/prebuilt/"*)
+[ -d "$toolchain" ] && \
+	export PATH="$toolchain/bin:$DIR/sdk/android-ndk-${v_ndk}:$DIR/sdk/bin:$PATH"
+export ANDROID_HOME="$DIR/sdk/android-sdk-$os"
+unset ANDROID_SDK_ROOT ANDROID_NDK_ROOT