# reyaansh72/mclauncher architecture

> Architecture diagram of the GitHub repository reyaansh72/mclauncher, generated by GitDiagram from its file tree, README and a sample of source files (last updated 2026-06-12). It is an AI-made overview: check details against the source.

- Interactive diagram: https://gitdiagram.com/reyaansh72/mclauncher
- Repository: https://github.com/reyaansh72/mclauncher

## Overview

1. **Overall shape**
   - MCLauncher is a **single-process desktop application** built in **Python + PySide6**.
   - The architecture is intentionally compact: most runtime behavior lives in `app.py`, with two small local data files for persistence and Java mapping.

2. **Primary subsystem: GUI launcher**
   - `app.py` owns the main window, controls, animations, and user interactions.
   - The UI is the entry point for selecting a Minecraft version, username, and RAM settings, then starting install/launch actions.

3. **Primary subsystem: version and metadata resolution**
   - The launcher reads the **official Mojang version manifest directly** to populate available Minecraft versions.
   - This is the source of truth for what can be installed, rather than a curated local catalog.

4. **Primary subsystem: installation pipeline**
   - The app handles the full client setup flow: downloading the version metadata, client jar, and required libraries.
   - The install flow is responsible for preparing a runnable local Minecraft version under the launcher’s managed game directory.

5. **Primary subsystem: Java selection**
   - Java runtime selection is driven by `java_rules.txt`.
   - The file maps Minecraft version ranges to a Java version and download URL, letting the launcher choose the correct runtime for older, current, and experimental releases.

6. **Primary subsystem: game execution**
   - After installation, `app.py` assembles the launch command and starts Minecraft via a subprocess.
   - The launcher supports both **offline/legacy launch behavior** and version-specific runtime selection, which is important for compatibility across old and new releases.

7. **State and persistence boundary**
   - `config.json` stores user-specific launcher state such as **username, selected version, and RAM**.
   - This separates ephemeral UI/session logic from persisted user preferences, so the app can restore settings across launches.

8. **Network and external dependencies**
   - The only major external service dependency is **Mojang’s official manifest and download endpoints**.
   - The app also downloads Java distributions referenced by `java_rules.txt`, making runtime selection partly data-driven.

9. **Platform boundary**
   - The project is explicitly **Linux-only**.
   - That constraint affects packaging, runtime assumptions, and the binary release strategy; Windows and macOS are not part of the supported architecture.

10. **Packaging and runtime model**
   - The repo is designed to run either from source or as a **PyInstaller-built single binary**.
   - Because the app is mostly self-contained, the packaged artifact only needs the Python runtime, PySide6, requests, and the bundled `java_rules.txt`.

11. **Data flow at a glance**
   - User input enters through the PySide6 UI in `app.py`.
   - The app reads `config.json` and `java_rules.txt`, fetches Mojang version data over the network, downloads required game/runtime files, then launches Minecraft locally.

12. **Architecture summary for diagramming**
   - Draw this as a **desktop UI core** with three local data inputs/outputs: persistent config, Java rule table, and managed Minecraft install directory.
   - Surround that core with two external dependencies: **Mojang services** for version/download metadata and **Java runtime downloads** for execution compatibility.

Main entry points: [`app.py`](https://github.com/reyaansh72/mclauncher/blob/main/app.py) (app.py), [`config.json`](https://github.com/reyaansh72/mclauncher/blob/main/config.json) (config.json), [`java_rules.txt`](https://github.com/reyaansh72/mclauncher/blob/main/java_rules.txt) (java_rules.txt)

## Diagram (Mermaid)

```mermaid
flowchart TD

subgraph group_core["Launcher core"]
  node_app_py["app.py<br/>desktop app<br/>[app.py]"]
  node_ui(("UI<br/>PySide6 view"))
  node_version_resolver["Version data<br/>manifest client"]
  node_installer["Installer<br/>setup pipeline"]
  node_runtime_selector["Java selector<br/>runtime rules"]
  node_launcher["Launch cmd<br/>subprocess launcher"]
end

subgraph group_state["Local state"]
  node_config_json[("config.json<br/>user config<br/>[config.json]")]
  node_java_rules_txt["java_rules.txt<br/>java map<br/>[java_rules.txt]"]
  node_game_dir[("Game dir<br/>managed files")]
end

subgraph group_external["External services"]
  node_mojang(("Mojang services<br/>manifest/download API"))
  node_java_dist(("Java distros<br/>runtime downloads"))
end

node_app_py -->|"renders"| node_ui
node_ui -->|"loads/saves"| node_config_json
node_ui -->|"requests versions"| node_version_resolver
node_version_resolver -->|"fetches manifest"| node_mojang
node_ui -->|"starts install"| node_installer
node_installer -->|"downloads game"| node_mojang
node_installer -->|"writes files"| node_game_dir
node_ui -->|"chooses runtime"| node_runtime_selector
node_runtime_selector -->|"reads rules"| node_java_rules_txt
node_runtime_selector -->|"resolves download"| node_java_dist
node_launcher -->|"uses install"| node_game_dir
node_launcher -->|"gets Java"| node_runtime_selector
node_launcher -->|"reads prefs"| node_config_json
node_app_py -->|"orchestrates"| node_installer
node_app_py -->|"orchestrates"| node_launcher

click node_app_py "https://github.com/reyaansh72/mclauncher/blob/main/app.py"
click node_config_json "https://github.com/reyaansh72/mclauncher/blob/main/config.json"
click node_java_rules_txt "https://github.com/reyaansh72/mclauncher/blob/main/java_rules.txt"

classDef toneNeutral fill:#f8fafc,stroke:#334155,stroke-width:1.5px,color:#0f172a
classDef toneBlue fill:#dbeafe,stroke:#2563eb,stroke-width:1.5px,color:#172554
classDef toneAmber fill:#fef3c7,stroke:#d97706,stroke-width:1.5px,color:#78350f
classDef toneMint fill:#dcfce7,stroke:#16a34a,stroke-width:1.5px,color:#14532d
classDef toneRose fill:#ffe4e6,stroke:#e11d48,stroke-width:1.5px,color:#881337
classDef toneIndigo fill:#e0e7ff,stroke:#4f46e5,stroke-width:1.5px,color:#312e81
classDef toneTeal fill:#ccfbf1,stroke:#0f766e,stroke-width:1.5px,color:#134e4a
class node_app_py,node_ui,node_version_resolver,node_installer,node_runtime_selector,node_launcher toneBlue
class node_config_json,node_java_rules_txt,node_game_dir toneAmber
class node_mojang,node_java_dist toneMint
```

## Components

### Launcher core

Single-process PySide6 launcher logic centered in app.py.

- [app.py](https://github.com/reyaansh72/mclauncher/blob/main/app.py): desktop app · Main window, controls, install flow, and launch orchestration. · `app.py`
- **UI**: PySide6 view · Version, username, RAM selection, and user actions.
- **Version data**: manifest client · Reads Mojang's official version manifest to populate installable releases.
- **Installer**: setup pipeline · Downloads version metadata, client jar, and libraries into the managed game directory.
- **Java selector**: runtime rules · Chooses a Java version and download URL from version ranges.
- **Launch cmd**: subprocess launcher · Assembles the game command and starts Minecraft locally.

### Local state

Persisted settings, rule data, and managed game files.

- [config.json](https://github.com/reyaansh72/mclauncher/blob/main/config.json): user config · Stores username, selected version, and RAM settings. · `config.json`
- [java_rules.txt](https://github.com/reyaansh72/mclauncher/blob/main/java_rules.txt): java map · Maps Minecraft version ranges to Java versions and download URLs. · `java_rules.txt`
- **Game dir**: managed files · Local Minecraft installation and downloaded libraries.

### External services

Remote dependencies for Minecraft metadata and Java downloads.

- **Mojang services**: manifest/download API · Official version manifest and game file download endpoints.
- **Java distros**: runtime downloads · External Java distributions used for version-specific runtime compatibility.

## Connections

- app.py → UI: renders · Creates the launcher interface and handles user input.
- UI → config.json: loads/saves · Restores and persists launcher preferences.
- UI → Version data: requests versions · Populates the version selector from the official manifest.
- Version data → Mojang services: fetches manifest · Reads available releases from Mojang.
- UI → Installer: starts install · Triggers the Minecraft setup flow for the selected version.
- Installer → Mojang services: downloads game · Fetches version metadata, client jar, and required libraries.
- Installer → Game dir: writes files · Places the installed version under the managed game directory.
- UI → Java selector: chooses runtime · Selects the Java runtime for the target Minecraft version.
- Java selector → java_rules.txt: reads rules · Uses local version-range mapping data.
- Java selector → Java distros: resolves download · Identifies the Java distribution to fetch when needed.
- Launch cmd → Game dir: uses install · Runs the installed client from the managed directory.
- Launch cmd → Java selector: gets Java · Uses the selected runtime for launch compatibility.
- Launch cmd → config.json: reads prefs · Uses persisted username, version, and RAM settings.
- app.py → Installer: orchestrates · Coordinates the install flow inside the main process.
- app.py → Launch cmd: orchestrates · Builds and starts the Minecraft subprocess.