ci: build Linux releases on Ubuntu 20.04 for compatibility

Change the Linux build platform from Ubuntu 22.04 to Ubuntu 20.04 so release packages target glibc 2.31 and install on Ubuntu 20.04.

docker/linux-build/Dockerfile

@@ -1,15 +1,16 @@
 # syntax=docker/dockerfile:1.7
 
-ARG BASE_IMAGE=nvidia/cuda:12.6.3-devel-ubuntu22.04
+ARG BASE_IMAGE=nvidia/cuda:12.6.3-devel-ubuntu20.04
 FROM ${BASE_IMAGE}
 
 ARG TARGETARCH
+ARG CMAKE_VERSION=3.31.6
 ARG XMAKE_VERSION=3.0.9
 ARG RUST_VERSION=1.92.0
 ARG RUSTUP_VERSION=1.28.2
 
 LABEL org.opencontainers.image.title="CrossDesk Linux build environment" \
-      org.opencontainers.image.description="Ubuntu 22.04 build environment for CrossDesk" \
+      org.opencontainers.image.description="Ubuntu 20.04 compatibility build environment for CrossDesk" \
       org.opencontainers.image.source="https://github.com/kunkundi/crossdesk" \
       org.opencontainers.image.licenses="GPL-3.0-only"
 
@@ -22,6 +23,8 @@ ENV DEBIAN_FRONTEND=noninteractive \
     XMAKE_GLOBALDIR=/data \
     XMAKE_ROOT=y \
     CUDA_PATH=/usr/local/cuda \
+    CC=/usr/bin/gcc-10 \
+    CXX=/usr/bin/g++-10 \
     PATH=/root/.local/bin:/opt/cargo/bin:/usr/local/bin:${PATH}
 
 SHELL ["/bin/bash", "-o", "pipefail", "-c"]
@@ -35,13 +38,14 @@ RUN apt-get update \
         build-essential \
         ca-certificates \
         ccache \
-        cmake \
         curl \
         dbus \
         dpkg-dev \
         file \
         flex \
         gettext \
+        gcc-10 \
+        g++-10 \
         git \
         libasound2-dev \
         libdbus-1-dev \
@@ -52,11 +56,9 @@ RUN apt-get update \
         libfreetype6-dev \
         libgl1-mesa-dev \
         libmount-dev \
-        libpipewire-0.3-dev \
         libpulse-dev \
         libreadline-dev \
         libsndio-dev \
-        libspa-0.2-dev \
         libssl-dev \
         libtool \
         libx11-dev \
@@ -95,6 +97,22 @@ RUN apt-get update \
         zlib1g-dev \
     && rm -rf /var/lib/apt/lists/*
 
+# Slint 1.17 requires CMake 3.21 or newer, while Ubuntu 20.04 provides 3.16.
+# PyPI publishes pinned manylinux2014 wheels for both amd64 and arm64.
+RUN python3 -m pip install --no-cache-dir "cmake==${CMAKE_VERSION}" \
+    && cmake --version | grep -F "cmake version ${CMAKE_VERSION}"
+
+# Ubuntu 20.04 only ships PipeWire 0.2. Install the Ubuntu 22.04-era 0.3.48
+# headers as a build-only SDK. CrossDesk loads the host's PipeWire 0.3 runtime
+# with dlopen(), so no PipeWire shared library is copied into release packages.
+COPY docker/linux-build/install-pipewire-sdk.sh \
+    /usr/local/bin/install-crossdesk-pipewire-sdk
+
+RUN chmod 0755 /usr/local/bin/install-crossdesk-pipewire-sdk \
+    && install-crossdesk-pipewire-sdk \
+    && grep -F "#define PW_MICRO 48" \
+        /opt/crossdesk-pipewire-sdk/include/pipewire-0.3/pipewire/version.h
+
 RUN export GITHUB_ACTIONS=true \
     && curl -fsSL https://xmake.io/shget.text \
         | bash -s -- "v${XMAKE_VERSION}" \
@@ -136,7 +154,8 @@ COPY submodules/minirtc/thirdparty ./submodules/minirtc/thirdparty
 # CrossDesk's exact dependency graph. Source files are intentionally excluded
 # from the Docker context; source-only changes therefore reuse this layer.
 RUN xmake repo -u --root \
-    && xmake f -m release --USE_CUDA=true --USE_WAYLAND=true --root -y \
+    && xmake f -m release --USE_CUDA=true --USE_WAYLAND=true \
+        --cc=gcc-10 --cxx=g++-10 --root -y \
     && rm -rf /data/.xmake/cache /tmp/crossdesk-dependencies \
     && mkdir -p /workspace
 

docker/linux-build/README.md

@@ -1,7 +1,8 @@
 # CrossDesk Linux 构建镜像
 
-这个目录维护 CrossDesk 专用的 Ubuntu 22.04 构建环境。镜像包含 xmake、
-Rust、Linux 开发库（包括 D-Bus、DRM、PipeWire 和 SPA）以及根据项目
+这个目录维护 CrossDesk 专用的 Ubuntu 20.04 兼容构建环境。镜像包含 GCC 10、
+CMake 3.31、xmake、Rust、Linux 开发库（包括 D-Bus、DRM，以及仅用于编译的
+PipeWire 0.3/SPA 头文件 SDK）以及根据项目
 `xmake.lua` 提前编译好的依赖。
 
 ## 发布方式
@@ -11,14 +12,19 @@ Rust、Linux 开发库（包括 D-Bus、DRM、PipeWire 和 SPA）以及根据项
 全部通过后再合并为同一个 multi-arch 镜像：
 
 ```text
-crossdesk/ubuntu22.04:buildenv-cuda12.6.3-xmake3.0.9-rust1.92.0
+crossdesk/ubuntu20.04:buildenv-cuda12.6.3-gcc10-cmake3.31.6-pipewire0.3.48-xmake3.0.9-rust1.92.0
 ```
 
 Docker 会根据运行机器自动选择正确架构。amd64 变体以
-`nvidia/cuda:12.6.3-devel-ubuntu22.04` 为基础；arm64 变体不包含当前构建
-用不到的 CUDA SDK。两个变体都使用 Ubuntu 22.04/glibc 2.35。
-因此该镜像生成的 Linux 安装包最低支持 Ubuntu 22.04，不再保证兼容
-Ubuntu 20.04。
+`nvidia/cuda:12.6.3-devel-ubuntu20.04` 为基础；arm64 变体不包含当前构建
+用不到的 CUDA SDK。两个变体都使用 Ubuntu 20.04/glibc 2.31，因此生成的
+单一 Linux 安装包可运行在 Ubuntu 20.04 及更高版本。
+
+Ubuntu 20.04 仓库只提供 PipeWire 0.2。镜像通过
+`install-pipewire-sdk.sh` 安装固定版本的 PipeWire 0.3.48/SPA 头文件，但不
+安装或打包 PipeWire 动态库。CrossDesk 在运行时通过 `dlopen()` 使用宿主系统
+提供的 PipeWire 0.3：Ubuntu 20.04 没有该运行库时仍可使用 X11（以及构建时
+启用的 DRM），Ubuntu 22.04 及更高版本则可使用 Wayland 捕获。
 
 每次成功发布还会生成 `sha-<完整提交 SHA>`，用于精确回滚；`latest` 和上面的
 工具链版本 tag 只会在两个架构都验证成功后更新。
@@ -27,7 +33,7 @@ Ubuntu 20.04。
 
 在仓库的 Actions secrets 中配置：
 
-- `DOCKERHUB_USERNAME`：有权推送 `crossdesk/ubuntu22.04` 的 Docker Hub 用户名
+- `DOCKERHUB_USERNAME`：有权推送 `crossdesk/ubuntu20.04` 的 Docker Hub 用户名
 - `DOCKERHUB_TOKEN`：该用户的 Docker Hub access token
 
 工作流文件进入默认分支后，也可以从 Actions 页面手动运行。为了避免首次发布

docker/linux-build/install-pipewire-sdk.sh

@@ -0,0 +1,55 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+PIPEWIRE_VERSION="0.3.48"
+PIPEWIRE_ARCHIVE_SHA256="0d218be86b3d2b548c06259c47ad8d110ee1c09f071e17c4393eeef5c880fa6f"
+INSTALL_PREFIX="${1:-/opt/crossdesk-pipewire-sdk}"
+IFS='.' read -r PIPEWIRE_VERSION_MAJOR PIPEWIRE_VERSION_MINOR \
+    PIPEWIRE_VERSION_MICRO <<< "${PIPEWIRE_VERSION}"
+
+if [[ "${INSTALL_PREFIX}" != /* ]]; then
+    echo "Install prefix must be an absolute path: ${INSTALL_PREFIX}" >&2
+    exit 2
+fi
+
+WORK_DIR="$(mktemp -d "${TMPDIR:-/tmp}/crossdesk-pipewire-sdk.XXXXXX")"
+trap 'rm -rf "${WORK_DIR}"' EXIT
+
+ARCHIVE_PATH="${WORK_DIR}/pipewire-${PIPEWIRE_VERSION}.tar.gz"
+SOURCE_DIR="${WORK_DIR}/pipewire-${PIPEWIRE_VERSION}"
+ARCHIVE_URL="https://gitlab.freedesktop.org/pipewire/pipewire/-/archive/${PIPEWIRE_VERSION}/pipewire-${PIPEWIRE_VERSION}.tar.gz"
+
+curl --proto '=https' --tlsv1.2 --fail --silent --show-error --location \
+    --retry 3 "${ARCHIVE_URL}" -o "${ARCHIVE_PATH}"
+echo "${PIPEWIRE_ARCHIVE_SHA256}  ${ARCHIVE_PATH}" | sha256sum --check -
+tar -xzf "${ARCHIVE_PATH}" -C "${WORK_DIR}"
+
+PIPEWIRE_INCLUDE_DIR="${INSTALL_PREFIX}/include/pipewire-0.3/pipewire"
+SPA_INCLUDE_DIR="${INSTALL_PREFIX}/include/spa-0.2/spa"
+
+while IFS= read -r -d '' header_path; do
+    relative_path="${header_path#${SOURCE_DIR}/src/pipewire/}"
+    install -D -m 0644 "${header_path}" \
+        "${PIPEWIRE_INCLUDE_DIR}/${relative_path}"
+done < <(find "${SOURCE_DIR}/src/pipewire" -type f -name '*.h' -print0)
+
+while IFS= read -r -d '' header_path; do
+    relative_path="${header_path#${SOURCE_DIR}/spa/include/spa/}"
+    install -D -m 0644 "${header_path}" \
+        "${SPA_INCLUDE_DIR}/${relative_path}"
+done < <(find "${SOURCE_DIR}/spa/include/spa" -type f -name '*.h' -print0)
+
+sed \
+    -e "s/@PIPEWIRE_VERSION_MAJOR@/${PIPEWIRE_VERSION_MAJOR}/g" \
+    -e "s/@PIPEWIRE_VERSION_MINOR@/${PIPEWIRE_VERSION_MINOR}/g" \
+    -e "s/@PIPEWIRE_VERSION_MICRO@/${PIPEWIRE_VERSION_MICRO}/g" \
+    -e 's/@PIPEWIRE_API_VERSION@/"0.3"/g' \
+    "${SOURCE_DIR}/src/pipewire/version.h.in" \
+    > "${PIPEWIRE_INCLUDE_DIR}/version.h"
+chmod 0644 "${PIPEWIRE_INCLUDE_DIR}/version.h"
+
+test -f "${PIPEWIRE_INCLUDE_DIR}/pipewire.h"
+test -f "${PIPEWIRE_INCLUDE_DIR}/version.h"
+test -f "${SPA_INCLUDE_DIR}/param/video/format-utils.h"
+
+echo "Installed PipeWire ${PIPEWIRE_VERSION} header SDK under ${INSTALL_PREFIX}"

docker/linux-build/verify-build-image.sh

@@ -2,19 +2,22 @@
 set -euo pipefail
 
 EXPECTED_ARCH="${EXPECTED_ARCH:-}"
+EXPECTED_CMAKE_VERSION="${EXPECTED_CMAKE_VERSION:-3.31.6}"
 EXPECTED_XMAKE_VERSION="${EXPECTED_XMAKE_VERSION:-3.0.9}"
 EXPECTED_RUST_VERSION="${EXPECTED_RUST_VERSION:-1.92.0}"
+BUILD_CC="${CC:-/usr/bin/gcc-10}"
+BUILD_CXX="${CXX:-/usr/bin/g++-10}"
 
 # shellcheck disable=SC1091
 source /etc/os-release
-if [[ "${ID}" != "ubuntu" || "${VERSION_ID}" != "22.04" ]]; then
-    echo "Expected Ubuntu 22.04, found ${ID:-unknown} ${VERSION_ID:-unknown}" >&2
+if [[ "${ID}" != "ubuntu" || "${VERSION_ID}" != "20.04" ]]; then
+    echo "Expected Ubuntu 20.04, found ${ID:-unknown} ${VERSION_ID:-unknown}" >&2
     exit 1
 fi
 
 GLIBC_VERSION="$(getconf GNU_LIBC_VERSION | awk '{print $2}')"
-if [[ "${GLIBC_VERSION}" != "2.35" ]]; then
-    echo "Expected glibc 2.35, found ${GLIBC_VERSION}" >&2
+if [[ "${GLIBC_VERSION}" != "2.31" ]]; then
+    echo "Expected glibc 2.31, found ${GLIBC_VERSION}" >&2
     exit 1
 fi
 
@@ -28,13 +31,23 @@ XMAKE_VERSION_OUTPUT="$(xmake --version 2>&1)"
 grep -F "v${EXPECTED_XMAKE_VERSION}" <<<"${XMAKE_VERSION_OUTPUT}" >/dev/null
 rustc --version | grep -F "rustc ${EXPECTED_RUST_VERSION}" >/dev/null
 cargo --version >/dev/null
-cmake --version >/dev/null
-g++ --version >/dev/null
+cmake --version | grep -F "cmake version ${EXPECTED_CMAKE_VERSION}" >/dev/null
+"${BUILD_CC}" --version | grep -F 'gcc-10' >/dev/null
+"${BUILD_CXX}" --version | grep -F 'g++-10' >/dev/null
+printf '%s\n' \
+    '#include <concepts>' \
+    '#include <span>' \
+    'template <typename T> concept TestConcept = true;' \
+    'int main() {' \
+    '    int value = 0;' \
+    '    std::span<int> values(&value, 1);' \
+    '    static_assert(TestConcept<int>);' \
+    '    return values.empty();' \
+    '}' \
+    | "${BUILD_CXX}" -std=c++20 -fsyntax-only -x c++ -
 for pkg_config_package in \
     dbus-1 \
     libdrm \
-    libpipewire-0.3 \
-    libspa-0.2 \
     xft; do
     if ! pkg-config --exists "${pkg_config_package}"; then
         echo "Required pkg-config package is missing: ${pkg_config_package}" >&2
@@ -42,6 +55,25 @@ for pkg_config_package in \
     fi
 done
 
+for sdk_header in \
+    /opt/crossdesk-pipewire-sdk/include/pipewire-0.3/pipewire/pipewire.h \
+    /opt/crossdesk-pipewire-sdk/include/pipewire-0.3/pipewire/version.h \
+    /opt/crossdesk-pipewire-sdk/include/spa-0.2/spa/param/video/format-utils.h; do
+    if [[ ! -f "${sdk_header}" ]]; then
+        echo "Required PipeWire build SDK header is missing: ${sdk_header}" >&2
+        exit 1
+    fi
+done
+
+printf '%s\n' \
+    '#include <pipewire/pipewire.h>' \
+    '#include <spa/param/video/format-utils.h>' \
+    'static_assert(PW_CHECK_VERSION(0, 3, 48));' \
+    'int main() { return 0; }' \
+    | "${BUILD_CXX}" -std=c++17 -fsyntax-only -x c++ \
+        -I/opt/crossdesk-pipewire-sdk/include/pipewire-0.3 \
+        -I/opt/crossdesk-pipewire-sdk/include/spa-0.2 -
+
 for package_path in \
     "s/slint" \
     "l/libdatachannel" \

docker/linux-build/verify-glibc-baseline.sh

@@ -7,7 +7,7 @@ if [[ $# -lt 1 || $# -gt 2 ]]; then
 fi
 
 INPUT_PATH="$1"
-MAXIMUM_VERSION="${2:-2.35}"
+MAXIMUM_VERSION="${2:-2.31}"
 
 verify_elf() {
     local elf_file="$1"