mirror of https://github.com/cutefishos/launcher
feat(dm): keep each user's desktop background for the login screen
reionwong
1 week ago
parent
578d0f9ff1
commit
876d8cf1b1
@ -0,0 +1,147 @@
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// SPDX-FileCopyrightText: 2026 Reion Wong <reionwong@gmail.com>
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// SPDX-License-Identifier: GPL-3.0-or-later
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#include "backgrounds.h"
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#include <cerrno>
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#include <filesystem>
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#include <optional>
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#include <string_view>
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#include <pwd.h>
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#include <sys/stat.h>
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#include <unistd.h>
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#include "base/file.h"
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#include "base/settings.h"
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using namespace cutefish;
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namespace dm {
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static constexpr std::string_view kSettingsSuffix = ".conf";
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static constexpr std::string_view kPictureSuffix = ".picture";
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static bool userExists(const std::string &user)
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{
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return getpwnam(user.c_str()) != nullptr;
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}
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static bool isColor(const std::string &color)
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{
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if (color.size() != 4 && color.size() != 7 && color.size() != 9)
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return false;
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if (color.front() != '#')
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return false;
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return color.find_first_not_of("0123456789abcdefABCDEF", 1) == std::string::npos;
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}
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// The whole file from its start, or nothing for anything but a regular file
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// within the limit. The descriptor is the caller's, so its offset is left alone.
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static std::optional<std::string> readPicture(int fd)
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{
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struct stat info = {};
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if (fstat(fd, &info) != 0 || !S_ISREG(info.st_mode) || info.st_size > Backgrounds::kMaximumPictureSize)
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return std::nullopt;
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std::string bytes;
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bytes.resize(size_t(info.st_size));
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size_t done = 0;
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while (done < bytes.size()) {
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const ssize_t count = pread(fd, bytes.data() + done, bytes.size() - done, off_t(done));
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if (count < 0 && errno == EINTR)
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continue;
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if (count <= 0)
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return std::nullopt;
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done += size_t(count);
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}
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return bytes.empty() ? std::nullopt : std::optional<std::string>(std::move(bytes));
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}
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Backgrounds::Backgrounds(std::string directory)
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: m_directory(std::move(directory))
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{
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}
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std::string Backgrounds::settingsPath(const std::string &user) const
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{
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return m_directory + '/' + user + std::string(kSettingsSuffix);
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}
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std::string Backgrounds::picturePath(const std::string &user) const
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{
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return m_directory + '/' + user + std::string(kPictureSuffix);
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}
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void Backgrounds::removeStale()
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{
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std::error_code error;
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for (const auto &entry : std::filesystem::directory_iterator(m_directory, error)) {
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const std::string name = entry.path().filename().string();
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std::string user;
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if (name.ends_with(kSettingsSuffix))
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user = name.substr(0, name.size() - kSettingsSuffix.size());
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else if (name.ends_with(kPictureSuffix))
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user = name.substr(0, name.size() - kPictureSuffix.size());
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if (user.empty() || !userExists(user))
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std::filesystem::remove(entry.path(), error);
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}
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}
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void Backgrounds::setPicture(const std::string &user, base::dbus::UnixFd file, std::function<void(bool)> done)
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{
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const uint64_t request = ++m_lastRequest;
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m_latest[user] = request;
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const std::string pending = picturePath(user) + '.' + std::to_string(request);
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m_copies[request] = base::ThreadPool::global().run(
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[file, pending] {
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const std::optional<std::string> bytes = readPicture(file.fd());
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return bytes && base::file::writeAtomically(pending, *bytes);
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},
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[this, user, request, pending, done = std::move(done)](bool copied) {
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m_copies.erase(request);
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if (!copied) {
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unlink(pending.c_str());
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done(false);
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return;
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}
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// A later request took over; it has its own answer.
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if (m_latest[user] != request) {
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unlink(pending.c_str());
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done(true);
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return;
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}
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const std::string picture = picturePath(user);
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if (rename(pending.c_str(), picture.c_str()) != 0) {
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unlink(pending.c_str());
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done(false);
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return;
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}
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base::Settings settings(settingsPath(user));
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settings.setValue("Appearance/BackgroundType", 0);
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settings.setValue("Appearance/Wallpaper", picture);
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done(settings.sync());
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});
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}
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bool Backgrounds::setColor(const std::string &user, const std::string &color)
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{
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if (!isColor(color))
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return false;
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m_latest[user] = ++m_lastRequest;
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base::Settings settings(settingsPath(user));
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settings.setValue("Appearance/BackgroundType", 1);
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settings.setValue("Appearance/BackgroundColor", color);
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return settings.sync();
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}
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} // namespace dm
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@ -0,0 +1,49 @@
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// SPDX-FileCopyrightText: 2026 Reion Wong <reionwong@gmail.com>
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// SPDX-License-Identifier: GPL-3.0-or-later
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#pragma once
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#include <cstdint>
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#include <functional>
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#include <map>
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#include <string>
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#include "base/dbus_types.h"
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#include "base/thread_pool.h"
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namespace dm {
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// Each user's desktop background as the login screen shows it, kept where the
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// greeter can read it: the user's home may be closed to it or not mounted yet.
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// <user>.conf has services.conf's [Appearance] keys, and <user>.picture is a
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// copy of the picture it names.
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class Backgrounds
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{
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public:
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// The largest picture copied, in bytes.
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static constexpr int64_t kMaximumPictureSize = 64 * 1024 * 1024;
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explicit Backgrounds(std::string directory);
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// Removes what belongs to no existing user, and copies left unfinished.
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void removeStale();
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// Copies the picture `file` reads, on a pool thread. done(false) for
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// anything but a readable regular file within kMaximumPictureSize. Of two
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// requests for one user, the later one wins whichever finishes first.
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void setPicture(const std::string &user, cutefish::base::dbus::UnixFd file, std::function<void(bool)> done);
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// #RGB, #RRGGBB or #AARRGGBB.
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bool setColor(const std::string &user, const std::string &color);
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std::string settingsPath(const std::string &user) const;
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std::string picturePath(const std::string &user) const;
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private:
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std::string m_directory;
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uint64_t m_lastRequest = 0;
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// The latest request for each user.
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std::map<std::string, uint64_t> m_latest;
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std::map<uint64_t, cutefish::base::Job> m_copies;
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};
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} // namespace dm
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