Calculator App in Rust egui — Grid Layout & Operator Logic | Learn egui Ep28

Build a fully functional calculator app in Rust using egui! In this episode, we create a calculator with a dark display panel, color-coded button grid (orange operators, gray numbers), and an operator state machine that handles chained arithmetic, decimals, percentage, negate, and division-by-zero errors. Student code: https://github.com/GoCelesteAI/egui_calculator What You'll Learn: - TopBottomPanel for a fixed calculator display - Button::new().fill() for custom button colors with Color32 - Horizontal layout with add_sized for consistent button grids - Operator state machine pattern (first, operator, reset_next) - String to f64 parsing for arithmetic - Wide zero button spanning two columns - Division by zero error handling - RichText with monospace font for the display - Frame with fill and corner_radius for styled panels - Layout::right_to_left for right-aligned display text - Neo-tree file browsing in a Rust project This is Episode 28 of the "Learn egui in Neovim" series — 36 episodes teaching Rust GUI development with egui, all coded in Neovim with Neo-tree. Chapters: 0:00 Intro 0:12 What We're Building 0:22 Preview: Key Concepts 0:54 Create Project & Dependencies 1:30 main.rs — Window Setup 2:30 app.rs — MyApp Struct 3:30 Default Implementation 4:30 press_digit Helper 5:30 press_operator Helper 6:00 evaluate — Arithmetic Logic 8:00 clear Helper 8:30 Review Helper Methods 9:00 eframe::App — Display Panel 10:00 Central Panel — Button Grid 10:30 Row Definitions 11:00 Button Styling (Orange/Gray) 12:00 Wide Zero Button 12:30 Click Handler — Match Label 14:00 Save & Review Code 15:00 cargo build 15:30 Neo-tree Browse 16:00 App Demo 17:00 Recap 17:40 Next Episode Tags: rust, egui, calculator, gui, tutorial, neovim, neo-tree, eframe, button, grid, state machine, color32, richtext, layout, panel, topbottompanel, add_sized, fill, parse, f64, operator, arithmetic, coding, programming, learn rust, rust gui, desktop app Hashtags: #rust #egui #calculator #gui #neovim #rustlang #coding #tutorial