dolphin/docs/autoupdate_overview.md

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# AutoUpdate Overview
Dolphin's autoupdate procedure is spread through a number of files; this overview describes the
update flow.
## General notes:
* The updater is only supported on Windows and MacOS.
* There are four update frequency tracks: Dev (updated every commit), Beta (a few times a year),
Stable (very rarely), and Disabled.
* Applications can't overwrite themselves so a separate application is responsible for actually
updating the Dolphin executable and other files.
* The updater application needs to be able to also update itself, so it creates a copy which
updates both Dolphin and the original updater. Every time Dolphin launches it deletes the
updater copy (if it exists).
## Class and file responsibilities:
* AutoUpdateChecker (UICommon/AutoUpdate.h): Checks if an update is available.
* Verifies the updater is supported on the user's platform and hasn't been disabled.
* Retrieves new version information from the update server.
* Copies the updater application and launches the copy.
* Updater (DolphinQt/Updater.h): Serves as the interface between AutoUpdateChecker and Qt.
* Spawns a background thread when Dolphin launches that calls AutoUpdateChecker.
* Creates the update prompt window when an update is available.
* If the user wants to update now, closes Dolphin.
* MacUpdater/main.m and MacUpdater/AppDelegate.mm: Entry point to MacOS updater.
* Converts command line arguments to vector\<string\> and passes them to
UpdaterCommon::RunUpdate().
* WinUpdater/main.cpp: Entry point to Windows updater.
* Converts command line arguments to vector\<string\>.
* Checks if updater has write access to the Dolphin executable directory. If not, attempts
to relaunch itself with admin privileges (creating a User Account Control prompt).
* Passes argument vector to UpdaterCommon::RunUpdate().
* UpdaterCommon/UpdaterCommon.cpp: Performs the actual update process.
* Manages updater UI.
* Fetches file manifests from update server for current and new versions.
* Calculates file diff between versions.
* Downloads and adds/replaces changed files and deletes removed files.
* Verifies file hashes.
* If the user updated immediately (rather than waiting for Dolphin to close before starting
the update), starts Dolphin again when the update is complete.
## Update flow:
* An update check is started in one of two ways:
* When Dolphin is launched (unless in NoGUI or batch mode):
* In main.cpp an instance of Updater is created and invokes start(), which is inherited
from QThread and creates a new thread which performs the check off the main thread.
* QThread::start() calls run() which is overridden in Updater and calls
AutoUpdateChecker::CheckForUpdate().
* When the user selects Help -> "Check for Updates..." in the main menu:
* The menu option runs a callback to MenuBar::InstallUpdateManually().
* The Config value for the update track is backed up to a temporary variable, then
overwritten with "dev" to force a check for the latest version. After the check
completes the original Config value is restored.
* Updater::CheckForUpdate() is called, which calls AutoUpdateChecker::CheckForUpdate().
* AutoUpdateChecker::CheckForUpdate() checks if the selected track has a new version available.
* If not the check ends. If the user started it, returns to Updater::CheckForUpdate() which
tells the user they're up to date.
* Information about the update is passed to OnUpdateAvailable(), which is overridden by Updater.
* OnUpdateAvailable() creates a window displaying the update changelog and asks the user if they
want to update now, update after Dolphin closes, not update, or never auto-update.
* If the user wants to update AutoUpdateChecker::TriggerUpdate() is called.
* TriggerUpdate() builds the command line arguments for the updater process, creates a copy of
the updater executable, then runs the copy in a new process.
* TriggerUpdate() returns to OnUpdateAvailable(). If the user chose to update now, Dolphin's
main window is closed which results in the Dolphin process ending.
* The updater process begins.
* On MacOS (starts main() in MacUpdater/main.m):
* Checks that the process received command line arguments. If not it tells the user the
updater can't be launched directly and quits.
* Calls NSApplicationMain(), which passes control to the AppDelegate defined in
MacUpdater/AppDelegate.mm.
* The command line arguments are converted to a vector\<string\>
and passed to RunUpdater() in UpdaterCommon.h.
* On Windows (starts wWinMain() in WinUpdater/Main.cpp):
* Checks that the process received command line arguments. If not it tells the user the
updater can't be launched directly and quits.
* Attempts to open Updater.log in the same directory as Dolphin.exe. If this fails,
checks to see if the process has admin privileges.
* If not, attempts to relaunch the updater as admin. This will spawn a User Account
Control prompt.
* If the user declines the UAC prompt, or if the updater already has admin status,
the update aborts.
* Converts the command line arguments to a vector\<string\> and passes them to RunUpdater()
in UpdaterCommon.h.
* RunUpdater() parses and validates the command line arguments, hides the updater UI, then waits
for the Dolphin process to quit.
* RunUpdater() begins the actual update.
* Fetches file manifests from update server for current and new versions.
* Decompresses manifests and verifies their signatures.
* Downloads and adds/replaces changed files and deletes removed files.
* Verifies downloaded files match manifest hashes.
* If the user updated immediately (rather than waiting for Dolphin to close before starting
the update), Dolphin restarts.
* As part of Dolphin's normal startup process, the Updater copy is deleted.