ci: build Linux releases on Ubuntu 20.04 for compatibility

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"