Route mods' Google Play sign-in requests to this launcher

Minecraft 1.26.50+ runs only with the mcpelauncher-updates mod, which asks
for the Google Play sign-in when the game starts. The engine looked for a
binary named mcpelauncher-ui-qt, which this app does not have, so the mod got
no credentials and the game crashed during startup.

- Engine patch: MCPELAUNCHER_UI_EXECUTABLE names the credentials helper; the
  launcher sets it to itself when it starts the game.
- The request window now has explicit Allow and Deny buttons, shows which mod
  is asking and for which account, and explains what to do when signed out
  instead of failing on a missing account.
- Play asks for Google sign-in first when not signed in (trial mode aside),
  including for versions installed by another launcher.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

README.md

@@ -43,6 +43,11 @@ right-click > Open (or System Settings > Privacy & Security > Open Anyway).
 Sign in with the Google account that bought Minecraft on Google Play. The
 sign-in is stored encrypted on disk; its key lives in the macOS Keychain.
 
+Minecraft 1.26.50 and newer also needs the `mcpelauncher-updates` mod, which the
+launcher offers to turn on. Each time the game starts, the mod asks to use your
+Google Play sign-in to confirm you own the game; the launcher shows that request
+and the game only starts once you allow it.
+
 **Windows**: run `AL-Arcade-MC-Launcher-<version>-windows-x64-setup.exe` (per-user
 install, no administrator rights needed) or unpack the portable `.zip`. The
 installer is not code-signed yet, so SmartScreen asks for More info > Run anyway.
@@ -140,6 +145,7 @@ overrides the built-in URL for testing.
 | Patch | Fixes |
 |---|---|
 | `mcpelauncher-core/0001-arm64-step-over-debug-breaks` | Debug break instructions in the game crashed or hung it on Apple Silicon; they are now stepped over |
+| `mcpelauncher-core/0002-ui-executable-from-environment` | Mods that ask for the Google Play sign-in reach this launcher (the engine looked for a binary named `mcpelauncher-ui-qt`) |
 | `mcpelauncher-client/0001-ignore-sigpipe` | The game quit when a network connection dropped (for example with a VPN) |
 | `mcpelauncher-client/0002-macos-fullscreen-shortcut` | Ctrl+Cmd+F toggles fullscreen; F11 is taken by macOS |
 | `game-window/0001-optional-non-retina-rendering` | Setting to render at half resolution on Retina screens for more frames per second |

launcher/gamelauncher.cpp

@@ -2,6 +2,7 @@
 #include "launchersettings.h"
 #include "profilemanager.h"
 #include "EnvPathUtil.h"
+#include <QCoreApplication>
 #include <QFile>
 #include <QDir>
 #include "supportedandroidabis.h"
@@ -32,6 +33,9 @@ void GameLauncher::start(bool disableGameLog, QString arch, bool hasVerifiedLice
     QStringList args;
     QStringList cargs;
     QProcessEnvironment env = QProcessEnvironment::systemEnvironment();
+    // Mods ask for Google Play credentials through the launcher; tell the engine
+    // where it is (patches/engine/mcpelauncher-core/0002).
+    env.insert("MCPELAUNCHER_UI_EXECUTABLE", QCoreApplication::applicationFilePath());
 #ifdef __APPLE__
     if (!LauncherSettings().retinaRendering())
         env.insert("ALARCADE_RETINA", "0");

launcher/qml/android/HomeScreen.qml

@@ -59,6 +59,10 @@ Item {
     }
     readonly property bool statusBlocking: !!statusMsg.title && statusMsg.tone !== "success"
     readonly property bool signedIn: googleLoginHelper.account !== null
+    // Owning the game is checked through Google Play, and the compatibility mod
+    // for new game versions asks for the sign-in at start, so playing the full
+    // game needs it even when the version was installed earlier.
+    readonly property bool needsSignInToPlay: !signedIn && !launcherSettings.trialMode
     // "1.26.52.3 (arm64-v8a, beta)" -> title "1.26.52.3", details "arm64-v8a, beta"
     readonly property string versionTitle: activeVersionName.split(" (")[0]
     readonly property string versionDetails: {
@@ -179,10 +183,16 @@ Item {
                         text: {
                             if (playScreen.statusChecking || !playScreen.activeVersionName)
                                 return ""
+                            if (playScreen.needsSignInToPlay)
+                                return qsTr("Sign in to play").toUpperCase()
                             return (playScreen.activeVersionNeedsDownload ? qsTr("Download and play") : qsTr("Play")).toUpperCase()
                         }
                         enabled: !(gameLauncher.running || playScreen.statusChecking || progressbarVisible || updateChecker.active || !playScreen.activeVersionSupported || !playScreen.activeVersionName || playScreen.statusBlocking)
                         onClicked: {
+                            if (playScreen.needsSignInToPlay) {
+                                actionSignIn()
+                                return
+                            }
                             if (playScreen.activeVersionNeedsDownload) {
                                 playDownloadTask.versionCode = getDownloadVersionCode()
                                 if (playDownloadTask.versionCode === 0)

launcher/qml/android/RequestGoogleCredentials.qml

 import QtQuick
 import QtQuick.Window
-import QtQuick.Dialogs
+import QtQuick.Layouts
 import QtQuick.Controls
-import Qt.labs.platform
 import io.mrarm.mcpelauncher 1.0
 import "../Components"
-import ".."
 
+// Started by the game engine (--request-google-credentials --mod <path>) when a
+// mod asks for the Google Play sign-in, before the game window opens. Allowing
+// prints CRED=<email>:<token> on stderr and exits 0; anything else exits 1.
 Window {
     id: window
+
     visible: true
-    width: 640
-    height: 480
-    title: qsTr("Request Google Credentials")
+    width: 560
+    height: 500
+    minimumWidth: 460
+    minimumHeight: 440
+    title: qsTr("%1: Google Play sign-in").arg(APP_NAME)
     color: Theme.background
+    flags: Qt.Window | Qt.WindowStaysOnTopHint
+
+    // Read by the upstream screens shown here.
     property bool hasUpdate: false
-    property bool hasAskedForKey: false
     property string updateDownloadUrl: ""
-    property bool isVersionsInitialized: false
     property string currentGameDataDir: ""
 
-    StackView {
-        id: stackView
-        anchors.fill: parent
+    property bool answered: false
+    property bool unlocking: googleLoginHelperInstance.hasEncryptedCredentials && googleLoginHelperInstance.account === null
+    readonly property var account: googleLoginHelperInstance.account
+    readonly property string mode: !googleLoginHelperInstance.isSupported() ? "unsupported" : account === null ? "signedOut" : "ask"
+
+    readonly property string modName: {
+        const parts = SOURCE_MOD.split("/").filter(part => part.length > 0)
+        const mods = parts.lastIndexOf("mods")
+        if (mods >= 0 && mods + 1 < parts.length)
+            return parts[mods + 1]
+        const file = parts.length > 0 ? parts[parts.length - 1] : ""
+        return file.replace(/^lib/, "").replace(/\.so$/, "") || qsTr("A mod")
     }
 
-    GoogleLoginHelper {
-        id: googleLoginHelperInstance
-        includeIncompatible: launcherSettings.showUnsupported
-        singleArch: launcherSettings.singleArch
-        chromeOS: launcherSettings.chromeOSMode || launcherSettings.trialMode
+    readonly property string maskedEmail: {
+        if (account === null)
+            return ""
+        const mail = account.accountIdentifier
+        const at = mail.indexOf("@")
+        if (mail.length < 4)
+            return mail
+        return mail.substring(0, 2) + "*".repeat(Math.max(3, (at > 2 ? at : mail.length) - 2)) + (at > 0 ? mail.substring(at) : "")
     }
 
-    Component {
-        id: panelError
-        ErrorScreen {
-            onFinished: defaultnext()
-        }
+    function allow() {
+        answered = true
+        stdio.error("CRED=" + account.accountIdentifier + ":" + account.accountToken)
+        stdio.error("CREDB64=" + Qt.btoa(JSON.stringify(account)))
+        application.exit(0)
     }
 
-    StdioHelper {
-        id: stdio
+    function deny() {
+        answered = true
+        application.exit(1)
     }
 
-    Component {
-        id: panelDefault
-        ErrorScreen {
-            message: qsTr("A mod at '%1'<br/>is requesting access to your google credentials,<br/>to reject this request close this window").arg(SOURCE_MOD)
-            onFinished: {
-                stdio.error("CRED=" + googleLoginHelperInstance.account.accountIdentifier + ":" + googleLoginHelperInstance.account.accountToken)
-                stdio.error("CREDB64=" + Qt.btoa(JSON.stringify(googleLoginHelperInstance.account)))
-                window.close()
-                application.quit()
-            }
-        }
+    onClosing: {
+        if (!answered)
+            deny()
     }
 
-    Component {
-        id: panelUnlock
-        UnlockScreen {
-            onFinished: {
-                next()
-            }
-        }
+    Component.onCompleted: {
+        raise()
+        requestActivate()
     }
 
     LauncherSettings {
         id: launcherSettings
     }
 
-    Connections {
-        target: window
-        function onClosing() {
-            application.quit()
-        }
-    }
-
-    function needsToLogIn() {
-        return googleLoginHelperInstance.account == null && !googleLoginHelperInstance.hasEncryptedCredentials && versionManagerInstance.versions.size === 0
+    StdioHelper {
+        id: stdio
     }
 
-    Component.onCompleted: {
-        next()
+    GoogleLoginHelper {
+        id: googleLoginHelperInstance
+        includeIncompatible: launcherSettings.showUnsupported
+        singleArch: launcherSettings.singleArch
+        chromeOS: launcherSettings.chromeOSMode || launcherSettings.trialMode
     }
 
-    function next() {
-        if (!googleLoginHelperInstance.isSupported()) {
-            stackView.push(panelError)
-        } else if (googleLoginHelperInstance.hasEncryptedCredentials && !hasAskedForKey) {
-            hasAskedForKey = true
-            stackView.push(panelUnlock)
-        } else {
-            defaultnext()
+    // Credentials protected by a password (older launcher versions) need it first.
+    Loader {
+        anchors.fill: parent
+        active: window.unlocking
+        sourceComponent: UnlockScreen {
+            onFinished: window.unlocking = false
         }
     }
 
-    function defaultnext() {
-        stackView.push(panelDefault)
+    Card {
+        anchors.centerIn: parent
+        width: Math.min(parent.width - 2 * Theme.space6, 480)
+        padding: Theme.space6
+        visible: !window.unlocking
+
+        ColumnLayout {
+            width: parent.width
+            spacing: Theme.space4
+
+            Rectangle {
+                Layout.alignment: Qt.AlignHCenter
+                implicitWidth: 52
+                implicitHeight: 52
+                radius: Theme.radiusLarge
+                color: window.mode === "ask" ? Theme.accentSoft : Theme.warningSoft
+                AppIcon {
+                    anchors.centerIn: parent
+                    iconName: window.mode === "ask" ? "shield-check" : "triangle-alert"
+                    size: 24
+                    color: window.mode === "ask" ? Theme.accentText : Theme.warning
+                }
+            }
+
+            Text {
+                Layout.fillWidth: true
+                horizontalAlignment: Text.AlignHCenter
+                wrapMode: Text.Wrap
+                color: Theme.text
+                font.pixelSize: Theme.fontHeading + 2
+                font.weight: Font.Bold
+                text: window.mode === "ask" ? qsTr("Allow %1 to use your Google Play sign-in?").arg(window.modName)
+                    : window.mode === "signedOut" ? qsTr("Sign in to Google Play first")
+                    : qsTr("Google Play is not available")
+            }
+
+            Text {
+                Layout.fillWidth: true
+                horizontalAlignment: Text.AlignHCenter
+                wrapMode: Text.Wrap
+                lineHeight: 1.15
+                color: Theme.textSecondary
+                font.pixelSize: Theme.fontBody
+                text: window.mode === "ask"
+                    ? qsTr("The mod is asking for the Google account you signed in with (%1), usually to confirm that you own Minecraft on Google Play. It gets access to that Google Play account, so allow only mods you trust.").arg(window.maskedEmail)
+                    : window.mode === "signedOut"
+                    ? qsTr("%1 needs your Google Play sign-in, but you are not signed in to %2. Open the launcher, sign in with the Google account that owns Minecraft and start the game again.").arg(window.modName).arg(APP_NAME)
+                    : qsTr("This build of %1 cannot use Google Play, so %2 cannot get a sign-in.").arg(APP_NAME).arg(window.modName)
+            }
+
+            Text {
+                Layout.fillWidth: true
+                visible: window.mode === "ask"
+                horizontalAlignment: Text.AlignHCenter
+                wrapMode: Text.Wrap
+                color: Theme.textMuted
+                font.pixelSize: Theme.fontSmall + 1
+                text: qsTr("If you deny, game versions that need this mod may not start.")
+            }
+
+            Rectangle {
+                Layout.fillWidth: true
+                visible: SOURCE_MOD.length > 0
+                implicitHeight: modPath.implicitHeight + 2 * Theme.space2
+                radius: Theme.radius
+                color: Theme.surfaceRaised
+                Text {
+                    id: modPath
+                    anchors.fill: parent
+                    anchors.margins: Theme.space2
+                    text: SOURCE_MOD
+                    color: Theme.textMuted
+                    font.family: Theme.fontMono
+                    font.pixelSize: Theme.fontCaption
+                    elide: Text.ElideMiddle
+                    verticalAlignment: Text.AlignVCenter
+                }
+            }
+
+            RowLayout {
+                Layout.fillWidth: true
+                Layout.topMargin: Theme.space2
+                spacing: Theme.space2
+
+                Item { Layout.fillWidth: true }
+                MButton {
+                    visible: window.mode === "ask"
+                    text: qsTr("Deny")
+                    onClicked: window.deny()
+                }
+                MButton {
+                    kind: "primary"
+                    text: window.mode === "ask" ? qsTr("Allow") : qsTr("Close")
+                    iconName: window.mode === "ask" ? "check" : ""
+                    onClicked: window.mode === "ask" ? window.allow() : window.deny()
+                }
+            }
+        }
     }
 }

patches/engine/mcpelauncher-core/0002-ui-executable-from-environment.patch

+Subject: Let the launcher tell the engine where its Google credentials helper is
+
+diff --git a/src/minecraft_utils.cpp b/src/minecraft_utils.cpp
+index d7f2360..f7a601b 100644
+--- a/src/minecraft_utils.cpp
++++ b/src/minecraft_utils.cpp
+@@ -129,6 +129,10 @@ struct GoogleCredentials {
+ };
+ 
+ static std::string getUiExecutablePath() {
++    // The launcher that started the game names itself here, whatever its file name.
++    const char* launcher = getenv("MCPELAUNCHER_UI_EXECUTABLE");
++    if(launcher && *launcher)
++        return launcher;
+     std::string path;
+ #ifndef MCPELAUNCHER_UI_PATH
+ #define MCPELAUNCHER_UI_PATH "."