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Let's create a minimal PDF package.

We'll build it without any dependencies, from the ground up by creating PDF objects, streams, drawing commands, pages and a complete document.

To keep things easier, we'll use PDF's built-in Courier fonts and support only ASCII. This way, we don't have to deal with measuring proportional text and parsing and embedding TrueType fonts.

PDF is a container format that contains (among other stuff) PDF objects. Those might contain streams of data and those data might be made up by PDF drawing commands. They might also contain dictionaries writting in << >> with keys whose symbolic names start with a /.

%PDF-1.7

%...

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Writing an EditableText from scratch

For a bit of retro fun, I created an AText widget that paints a text using a crisp pixel font without antialiasing, something Text isn't capable of. Here's the API:

class AText(
  final String data, {
  final TextStyle? style,
})

For compatibility, I support a TextStyle but ignore everything but the color property. The font has a width and height of 8 pixels.

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Flutter Native

So you think React Native is better than Flutter because it uses native UI elements instead of rendering everything itself? Well, then let’s build the same thing for Flutter. I'll do it for macOS. Feel free to do it yourself for your platform instead.

Project Setup

Start like this.

flutter create --platforms=macos --empty flutter_native

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Analyzer Plugin Demo

This explains how to write a simple analyzer plugin.

Create a Dart project called demo_plugin and add these dependencies to pubspec.yaml. The versions shown below should work with Dart 3.13. You might need to adapt them to your Dart version.

dependencies:
  analysis_server_plugin: ^0.3.20
  analyzer: ^14.1.0

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Building a FOCAL Interpreter in Dart

The Sumerian Game is one of the oldest computer games, created in 1964 as an education game. Its source code is unfortunately lost, but a simplified version was ported in 1969 to FOCAL for the PDP8 under the name King of Sumeria and then to BASIC around 1971 and eventually published as Hamurabi in David Ahl's 101 BASIC Computer Games book.

What's This All About?

This tutorial shows how to build a FOCAL interpreter from scratch.

Here's the original* Hamurabi program we'll run:

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People always ask for the best way to store data.

Most often they don't disclose their requirements. So let's assume a) we only need to store a few megabytes of data (which easily fit into the main memory of your device), b) we have more reads than writes, c) we need only be faster than 1ms, and d) we don't need complex queries. A simple key/value store will suffice.

Here's a minimal key-value store API:

abstract class KV<T> {
  Future<T?> get(String key);
  Future<void> set(String key, T value);

Future delete(String key);

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A tiny server UI framework

Let's iteratively create the components to create Flutter UIs from textual descriptions. How to create those descriptions or how you get them from some server shall be out of scope.

A simple HTTP REST is probably sufficient, but especially for debugging, a parallel web socket channel or server side events (SSEs) would be useful to trigger a redisplay as if the app was hot-reloaded. For production, consider caching all responses.

Hierarchical nodes

Here's a generic hierarchical Node class which will be our main building block:

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(Mit diem selben Prompt habe ich "Optimus Alpha", ein "Stealth"-Model auf Openrouter ausprobiert, wo unbekannt ist, wer der Hersteller ist. Bei dem Namen würde ich auf X.AI tippen. Der Anhang stammt wieder aus einem eigenen Prompt.)

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ÄTHERSPANNUNG

Abenteuer im elektrifizierten Berlin 1900

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INHALT

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Funken & Schatten

Ein Rollenspiel voller Erfindungen, Intrigen und Abenteuer im elektrifizierten Kaiserreich

Inhaltsverzeichnis:

1. Einleitung: Willkommen bei Funken & Schatten
2. Die Grundpfeiler des Spiels
3. Charaktererschaffung

• Attribute

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Writing a Dice Roller MCP Server in Dart

Let's write a MCP server in Dart. I'd like to make a tool that knows how to roll dice. This way, an LLM can get access to a real source of randomnes.

There's no ready-to-use Dart package, but there's a specification that details how to create such a server.

In its easiest form, the server reads JSON RPC requests from stdin and writes responses to stdout. It is allowed to use stderr for logging. All streams are UTF-8 encoded and adhere to the JSONL format, that is, each request must be a single line.

RPC