fix: ensure XDG_DATA_DIRS contains system dirs so Vulkan drivers load

[btlqql]

Summary

Fixes #1457 — Mesa3D Snapdragon Turnip (freedreno) Vulkan driver fails to load inside Linglong containers, while OpenGL works.

Root cause

The Vulkan ICD loader discovers driver manifests by scanning each entry of XDG_DATA_DIRS for a vulkan/icd.d subdirectory, and only falls back to /usr/local/share:/usr/share when XDG_DATA_DIRS is unset.

Inside a Linglong container the host XDG_DATA_DIRS — which on a Linyaps session points at Linyaps specific paths such as /var/lib/linglong/entries/share — can be forwarded into the container environment (e.g. via forwardEnv()). That overrides the loader's default search path, so the loader never scans /usr/share/vulkan/icd.d and enumerates no GPU.

This perfectly matches the reported symptoms:

• OpenGL works — Mesa locates DRI drivers through the compiled-in library path, independent of XDG_DATA_DIRS.
• Vulkan fails — the loader relies on XDG_DATA_DIRS-based discovery.
• VK_ICD_FILENAMES=... works around it (as the maintainer confirmed), because that variable bypasses the directory search.

Fix

In ContainerCfgBuilder::buildEnv() (the central place where the container environment is assembled, used by both the ll-cli and UAB paths), ensure the conventional system data directories /usr/share and /usr/local/share are always part of XDG_DATA_DIRS:

• preserve any existing/forwarded value (host specific paths are kept),
• append the standard system directories when missing,
• avoid duplicates and avoid rewriting the value when nothing changes.

This lets the Vulkan loader (and any other XDG-data consumer) keep discovering system-provided data such as the Mesa Turnip driver manifest at /usr/share/vulkan/icd.d, without requiring users to export VK_ICD_FILENAMES.

Files changed

• libs/oci-cfg-generators/src/linglong/oci-cfg-generators/container_cfg_builder.cpp — normalize XDG_DATA_DIRS in buildEnv().
• libs/linglong/tests/ll-tests/src/linglong/oci_cfg_generators/container_cfg_builder_test.cpp — new regression tests.
• libs/linglong/tests/ll-tests/CMakeLists.txt — register the new test source.

Verification

Configured with cmake --preset debug and built linglong::linglong::ll-tests:

cmake --build build --target linglong__linglong__ll-tests

Ran the new tests plus the surrounding runtime/env suites:

./ll-tests --gtest_filter='ContainerCfgBuilderEnvTest.*:RunContextTest.*:RunContainerOptionsTest.*'

Result: 23/23 passed. The three new tests cover:

1. XDG_DATA_DIRS unset → defaults added (/usr/share, /usr/local/share).
2. host value forwarded → preserved, with system dirs appended.
3. system dirs already present → no duplication, value untouched.

Full suite: 460 passed, 12 skipped (FUSE/display), 1 failure (Error.WarpStdErrorCode) which is pre-existing and environmental — it expects a non-root runner, while the CI sandbox runs as root so create_directory("/no_permission_to_create") succeeds.

clang-format --dry-run --Werror passes on both changed source files.

Risk / assumptions

• The change only ever adds the standard system data directories to XDG_DATA_DIRS; it never removes existing entries, so application/desktop-entry data discovery is unaffected.
• This addresses ICD discovery. It assumes the runtime/base layer actually ships the driver manifest (the base runtime's mesa-vulkan-drivers provides the freedreno ICD, as confirmed by the maintainer's test showing driver Mesa 24.3.0-1deepin1).

[deepin-ci-robot]

Welcome @btlqql! It looks like this is your first PR to OpenAtom-Linyaps/linyaps 🎉

[deepin-ci-robot]

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This pull-request has been approved by: btlqql

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[deepin-ci-robot]

Hi @btlqql. Thanks for your PR.

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[gemini-code-assist]

Code Review

This pull request ensures that conventional system data directories (/usr/local/share and /usr/share) remain reachable through XDG_DATA_DIRS in the container environment, which is necessary for the Vulkan ICD loader to discover system-provided driver manifests. It also adds corresponding unit tests to verify this behavior. The reviewer suggested optimizing the environment variable building logic to avoid unnecessary string copying and heap allocations when the system directories are already present.

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[gemini-code-assist]

We can optimize this block to avoid unnecessary string copying and heap allocations:

1. Use std::string_view for currentValue instead of copying xdgIt->second into a new std::string.
2. Check if the system directories are already present in entries before allocating and copying elements into dirs. If they are already present, we can skip the entire update process entirely.

        const std::vector<std::string> systemDataDirs{ "/usr/local/share", "/usr/share" };
        auto xdgIt = environment.find("XDG_DATA_DIRS");
        std::string_view currentValue = (xdgIt != environment.end()) ? std::string_view{xdgIt->second} : std::string_view{};
        auto entries =
          common::strings::split(currentValue, ':', common::strings::splitOption::SkipEmpty);

        bool changed = (xdgIt == environment.end());
        if (!changed) {
            for (const auto &dir : systemDataDirs) {
                if (std::find(entries.begin(), entries.end(), dir) == entries.end()) {
                    changed = true;
                    break;
                }
            }
        }

        if (changed) {
            std::vector<std::string> dirs;
            dirs.reserve(entries.size() + systemDataDirs.size());
            for (auto entry : entries) {
                dirs.emplace_back(entry);
            }
            for (const auto &dir : systemDataDirs) {
                if (std::find(dirs.begin(), dirs.end(), dir) == dirs.end()) {
                    dirs.push_back(dir);
                }
            }
            environment["XDG_DATA_DIRS"] = common::strings::join(dirs, ':');
        }