From 81e326571bb31dc4a92f1dbe32cb3ec50ace71f8 Mon Sep 17 00:00:00 2001
From: flow <flowlnlnln@gmail.com>
Date: Thu, 15 Sep 2022 19:23:58 -0300
Subject: [PATCH] fix: enable demo launch only on supported instances

e.g. >= 1.3.1 instances

Signed-off-by: flow <flowlnlnln@gmail.com>
---
 launcher/minecraft/MinecraftInstance.cpp |  8 ++++++++
 launcher/minecraft/MinecraftInstance.h   |  2 ++
 launcher/ui/InstanceWindow.cpp           |  8 +++++++-
 launcher/ui/MainWindow.cpp               | 14 ++++++++++++++
 4 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/launcher/minecraft/MinecraftInstance.cpp b/launcher/minecraft/MinecraftInstance.cpp
index 9478b1b8..ab904fa2 100644
--- a/launcher/minecraft/MinecraftInstance.cpp
+++ b/launcher/minecraft/MinecraftInstance.cpp
@@ -245,6 +245,14 @@ QString MinecraftInstance::getLocalLibraryPath() const
     return libraries_dir.absolutePath();
 }
 
+bool MinecraftInstance::supportsDemo() const
+{
+    Version instance_ver { getPackProfile()->getComponentVersion("net.minecraft") };
+    // Demo mode was introduced in 1.3.1: https://minecraft.fandom.com/wiki/Demo_mode#History
+    // FIXME: Due to Version constraints atm, this can't handle well non-release versions
+    return instance_ver >= Version("1.3.1");
+}
+
 QString MinecraftInstance::jarModsDir() const
 {
     QDir jarmods_dir(FS::PathCombine(instanceRoot(), "jarmods/"));
diff --git a/launcher/minecraft/MinecraftInstance.h b/launcher/minecraft/MinecraftInstance.h
index d62ac655..fe39674a 100644
--- a/launcher/minecraft/MinecraftInstance.h
+++ b/launcher/minecraft/MinecraftInstance.h
@@ -69,6 +69,8 @@ public:
     // where the instance-local libraries should be
     QString getLocalLibraryPath() const;
 
+    /** Returns whether the instance, with its version, has support for demo mode. */
+    [[nodiscard]] bool supportsDemo() const;
 
     //////  Profile management //////
     std::shared_ptr<PackProfile> getPackProfile() const;
diff --git a/launcher/ui/InstanceWindow.cpp b/launcher/ui/InstanceWindow.cpp
index 5bf42bb5..09ce0d67 100644
--- a/launcher/ui/InstanceWindow.cpp
+++ b/launcher/ui/InstanceWindow.cpp
@@ -166,7 +166,13 @@ void InstanceWindow::updateLaunchButtons()
     else
     {
         m_launchOfflineButton->setEnabled(true);
-        m_launchDemoButton->setEnabled(true);
+
+        // Disable demo-mode if not available.
+        auto instance = dynamic_cast<MinecraftInstance*>(m_instance.get());
+        if (instance) {
+            m_launchDemoButton->setEnabled(instance->supportsDemo());
+        }
+
         m_killButton->setText(tr("Launch"));
         m_killButton->setObjectName("launchButton");
         m_killButton->setToolTip(tr("Launch the instance"));
diff --git a/launcher/ui/MainWindow.cpp b/launcher/ui/MainWindow.cpp
index 9b195d26..58b1ae80 100644
--- a/launcher/ui/MainWindow.cpp
+++ b/launcher/ui/MainWindow.cpp
@@ -1253,6 +1253,13 @@ void MainWindow::updateToolsMenu()
         normalLaunchOffline->setDisabled(true);
         normalLaunchDemo->setDisabled(true);
     }
+
+    // Disable demo-mode if not available.
+    auto instance = dynamic_cast<MinecraftInstance*>(m_selectedInstance.get());
+    if (instance) {
+        normalLaunchDemo->setEnabled(instance->supportsDemo());
+    }
+
     QString profilersTitle = tr("Profilers");
     launchMenu->addSeparator()->setText(profilersTitle);
     launchOfflineMenu->addSeparator()->setText(profilersTitle);
@@ -2164,6 +2171,13 @@ void MainWindow::instanceChanged(const QModelIndex &current, const QModelIndex &
         ui->actionLaunchInstance->setEnabled(m_selectedInstance->canLaunch());
         ui->actionLaunchInstanceOffline->setEnabled(m_selectedInstance->canLaunch());
         ui->actionLaunchInstanceDemo->setEnabled(m_selectedInstance->canLaunch());
+
+        // Disable demo-mode if not available.
+        auto instance = dynamic_cast<MinecraftInstance*>(m_selectedInstance.get());
+        if (instance) {
+             ui->actionLaunchInstanceDemo->setEnabled(instance->supportsDemo());
+        }
+
         ui->actionKillInstance->setEnabled(m_selectedInstance->isRunning());
         ui->actionExportInstance->setEnabled(m_selectedInstance->canExport());
         ui->renameButton->setText(m_selectedInstance->name());