# Design Document

## Overview

This design outlines a simple, cross-platform demo application built with GLFW3 for window management and Nuklear for immediate mode GUI rendering. The application is designed to be minimal and straightforward, serving as a basic example of integrating these technologies.

The core design principle is simplicity - create a working demo that shows basic Nuklear GUI elements in a GLFW window with minimal code complexity.

## Architecture

The application uses a simple, single-file architecture:

```
┌─────────────────────────────────┐
│         Main Application        │  ← Single main.c file
│  ┌─────────────────────────────┐ │
│  │    GLFW3 Window Setup       │ │  ← Window creation & events
│  ├─────────────────────────────┤ │
│  │    Nuklear Integration      │ │  ← GUI context & rendering
│  ├─────────────────────────────┤ │
│  │    Simple UI Demo           │ │  ← Basic UI components
│  └─────────────────────────────┘ │
└─────────────────────────────────┘
```

### Key Design Decisions

1. **Single File**: Everything in one main.c file for simplicity
2. **OpenGL Backend**: Using Nuklear's OpenGL3 backend for cross-platform compatibility
3. **Minimal Dependencies**: Only GLFW3, OpenGL, and Nuklear (header-only)
4. **Basic UI Elements**: Simple buttons, text, and input fields for demonstration

## Components and Interfaces

### Main Application Structure
The application consists of simple functions organized in a single file:

```c
// Core application functions
int main(int argc, char** argv);
void init_glfw(void);
void init_nuklear(void);
void render_ui(struct nk_context* ctx);
void cleanup(void);

// Simple state variables
static GLFWwindow* window;
static struct nk_context* ctx;
static int window_width = 800;
static int window_height = 600;
```

### Basic UI Demo Functions
Simple functions to demonstrate different Nuklear UI elements:

```c
// Demo UI functions
void demo_basic_widgets(struct nk_context* ctx);
void demo_text_input(struct nk_context* ctx);
void demo_buttons(struct nk_context* ctx);
```

## Data Models

### Simple State Variables
The demo uses minimal global state:

```c
// UI state for demo
static char text_buffer[256] = "Hello World!";
static float slider_value = 0.5f;
static int checkbox_value = 1;
static int option_selected = 0;
```

## Error Handling

### Simple Error Handling
Basic error checking with immediate exit on failure:

```c
// Simple error checking pattern
if (!glfwInit()) {
    fprintf(stderr, "Failed to initialize GLFW\n");
    exit(EXIT_FAILURE);
}

if (!window) {
    fprintf(stderr, "Failed to create window\n");
    glfwTerminate();
    exit(EXIT_FAILURE);
}
```

## Testing Strategy

### Manual Testing
- **Build Testing**: Verify compilation on Windows, Linux, and macOS
- **Visual Testing**: Ensure UI elements render correctly
- **Interaction Testing**: Test basic button clicks, text input, and sliders
- **Window Testing**: Test window resize and close functionality

## Implementation Notes

### Build System
- **Simple Makefile or CMake**: Basic build configuration
- **Dependencies**: GLFW3, OpenGL, Nuklear (single header file)
- **Compiler**: C99 standard for maximum compatibility

### File Structure
```
project/
├── main.c              # Single source file
├── nuklear.h           # Nuklear header (downloaded)
├── nuklear_glfw_gl3.h  # Nuklear GLFW+OpenGL3 backend
├── CMakeLists.txt      # Build configuration
└── README.md           # Build instructions
```

### Cross-Platform Notes
- Use GLFW3 for consistent window management across platforms
- OpenGL 3.3 core profile for modern graphics support
- Standard C library functions only for maximum portability