05_game_loop_integration

05 - Game Loop Integration

This example demonstrates a complete game loop integration combining event-driven architecture with input polling.

What This Example Shows

1. Game Loop Structure: Complete game loop with event processing, update, and render phases
2. Event Processing: Processing events at the start of each frame
3. Input Polling: Polling input state during the update phase
4. Combined Approach: Using both events and polling together
5. Frame-Based State: Per-frame input state management with nextFrame()

Building

cd build
cmake .. -DBUILD_EXAMPLES=ON
cmake --build .

Running

./bin/examples/example_05_game_loop_integration

Expected Output

[INFO] [vneevents.examples] VneEvents Example: Game Loop Integration
[INFO] [vneevents.examples] ========================================
[INFO] [vneevents.examples] 
[INFO] [vneevents.examples] === Game Loop Integration Demonstration ===
[INFO] [vneevents.examples] 
[INFO] [vneevents.examples] --- Game Loop Simulation ---
[INFO] [vneevents.examples]   Registered event listeners
[INFO] [vneevents.examples]   Starting game loop (5 frames)...
[INFO] [vneevents.examples] 
[INFO] [vneevents.examples] --- Frame 1 ---
[INFO] [vneevents.examples]   [Event] Window resized to: 1920x1080
[INFO] [vneevents.examples]     [Update] No movement input
[INFO] [vneevents.examples]     [Render] Rendering frame (player at: 0, 0)
[INFO] [vneevents.examples] 
[INFO] [vneevents.examples] --- Frame 2 ---
[INFO] [vneevents.examples]     [Update] No movement input
[INFO] [vneevents.examples]     [Render] Rendering frame (player at: 0, 0)
[INFO] [vneevents.examples] 
[INFO] [vneevents.examples] --- Frame 3 ---
[INFO] [vneevents.examples]   [Event] Key pressed: 32
[INFO] [vneevents.examples]     [Update] Space key just pressed - jump action!
[INFO] [vneevents.examples]     [Update] No movement input
[INFO] [vneevents.examples]     [Render] Rendering frame (player at: 0, 0)
[INFO] [vneevents.examples] 
[INFO] [vneevents.examples] --- Frame 4 ---
[INFO] [vneevents.examples]     [Update] No movement input
[INFO] [vneevents.examples]     [Render] Rendering frame (player at: 0, 0)
[INFO] [vneevents.examples] 
[INFO] [vneevents.examples] --- Frame 5 ---
[INFO] [vneevents.examples]   [Event] Window close requested
[INFO] [vneevents.examples]     [Update] No movement input
[INFO] [vneevents.examples]     [Render] Rendering frame (player at: 0, 0)
[INFO] [vneevents.examples] 
[INFO] [vneevents.examples] === Demonstration Complete ===
[INFO] [vneevents.examples] 
[INFO] [vneevents.examples] === Done ===

Key Concepts

Game Loop Structure

A typical game loop follows this pattern:

while (running) {
    // 1. Process events (from platform callbacks)
    processEvents();
    
    // 2. Update game state (poll input, update entities)
    update(delta_time);
    
    // 3. Render the frame
    render();
    
    // 4. Reset per-frame input state
    Input::nextFrame();
}

Event Processing

• Events are pushed by platform callbacks (GLFW, SDL, etc.)
• Process all events at the start of each frame
• Events handle discrete actions (window close, key press, etc.)

Input Polling

• Poll input state during the update phase
• Use isKeyPressed() for continuous input (movement)
• Use isKeyJustPressed() for single-press actions (jump, shoot)
• Always call nextFrame() at the end of the frame

Combined Approach

• Events: Best for discrete actions (window close, key press events)
• Polling: Best for continuous input (movement, camera control)
• Both: Use events to update input state, poll for game logic

Code Structure

• main.cpp: Minimal setup, uses LoggingGuard_C and calls GameLoopDemo::run()
• game_loop_demo.h / game_loop_demo.cpp: Helper class encapsulating the game loop logic
• common/logging_guard.h: Shared logging configuration for all examples

Real-World Usage

In a real game engine:

1. Platform Layer: Window callbacks push events and update input state
2. Event System: Processes events for UI, window management, etc.
3. Game Logic: Polls input state for player movement, camera control
4. Render System: Renders the scene based on current game state

This example simulates this architecture without requiring a windowing system.