Gui (SDL2 Graphics)

Low-level 2D graphics, games, and creative coding. Uses SDL2 for cross-platform rendering with pixel-level control.

For desktop applications with system fonts and HTML/CSS, use the App module instead.

Prerequisites

# macOS
brew install sdl2

# Linux
apt install libsdl2-dev

Quick Start

fn main() {
    Gui.create("My Game", 800, 600)
    while Gui.running() > 0 {
        var ev = Gui.poll()
        if ev.split_at("|", 0) == "key" {
            if ev.split_at("|", 1).to_int() == 27 { break }
        }
        Gui.clear(30, 30, 40)
        Gui.color(255, 100, 100)
        Gui.rect(100, 100, 200, 150)
        Gui.color(255, 255, 255)
        Gui.text(100, 80, "Hello!", 2)
        Gui.present()
        Gui.delay(16)
    }
    Gui.destroy()
}

API

Window

Method	Description
Gui.create(title, w, h) -> int	Create window (-1 on failure)
Gui.destroy()	Close window
Gui.running() -> int	1 if window is open
Gui.width() -> int	Window width
Gui.height() -> int	Window height
Gui.present()	Flip buffer to screen
Gui.delay(ms)	Wait (use 16 for ~60fps)

Drawing

Method	Description
Gui.clear(r, g, b)	Clear screen with color
Gui.color(r, g, b)	Set draw color (0-255)
Gui.rect(x, y, w, h)	Filled rectangle
Gui.rect_outline(x, y, w, h)	Rectangle outline
Gui.line(x1, y1, x2, y2)	Line
Gui.point(x, y)	Single pixel
Gui.circle(cx, cy, r)	Filled circle

Text

Method	Description
Gui.text(x, y, text, scale)	Draw text (built-in 5x7 pixel font, scale 1-4)

Widgets

Method	Description
Gui.panel(x, y, w, h)	Dark panel background
Gui.button(x, y, w, h, label)	Draw button
Gui.button_clicked(x, y, w, h, mx, my) -> int	Check if mouse is in button area
Gui.label(x, y, text, scale)	Alias for text
Gui.progress(x, y, w, h, pct)	Progress bar (0-100)

Input

Method	Description
Gui.poll() -> string	Get event: "key|code|mod", "mouse|x|y|btn", "quit|0|0|0"
Gui.key_pressed(keycode) -> int	1 if key is currently held
Gui.mouse_x() -> int	Current mouse X
Gui.mouse_y() -> int	Current mouse Y
Gui.mouse_down() -> int	1 if left button held
Gui.ticks() -> int	Milliseconds since start

When to Use Gui vs App

	Gui (SDL2)	App (WebView)
Use for	Games, graphics, pixel art	Desktop apps, forms, dashboards
Fonts	Built-in pixel font	System fonts (CSS)
Layout	Manual coordinates	HTML/CSS
Styling	Color + rect	Full CSS
Binary size	~50KB + SDL2	~50KB (no deps on macOS)