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GameEngine

Code: include/core/GameEngine.hpp, src/core/GameEngine.cpp

Overview

GameEngine coordinates the main loop, display/window state, manager initialization, GameState execution, and the render/present split.

Rendering and timing details:

  • display refresh is propagated into TimestepManager
  • VSync is controlled through swapchain present mode

Main Loop Shape

ts.startFrame();
engine.handleEvents();

while (ts.shouldUpdate()) {
    engine.update(ts.getUpdateDeltaTime());
}

engine.render();
engine.present();
ts.endFrame();

render() performs scene/UI rendering. present() completes the frame. GameStates must not call SDL_RenderPresent() or SDL_RenderClear() directly.

Display Refresh Propagation

GameEngine::updateDisplayRefreshRate() reads the active display mode and calls:

m_timestepManager->setDisplayRefreshHz(refreshHz);

This does not change the fixed simulation rate. It allows TimestepManager to quantize render deltas against the real display cadence and reduce drift on VSync-paced systems.

Rendering

  • getWidthInPixels() / getHeightInPixels() are the authoritative dimensions for swapchain, viewport, scene texture, and UI layout work
  • present pacing happens when the swapchain texture is acquired and the frame command buffer is submitted
  • GPURenderer owns swapchain present mode and pass sequencing
  • if the swapchain texture cannot be acquired for a frame, rendering can be skipped cleanly

Platform Notes

GPU backend preference

The engine requests the platform-native backend that matches the compiled shader binaries:

  • Windows: Direct3D 12
  • macOS: Metal
  • Linux and other non-Apple Unix platforms: Vulkan

On macOS this keeps the GPU path aligned with current display refresh handling, including ProMotion-style refresh reporting when available.

Resizing / display changes

Window/display changes feed back into:

  • display refresh propagation to TimestepManager
  • cached logical window size plus pixel-space viewport/UI updates
  • swapchain-authoritative GPU viewport sizing
  • font DPI refresh on platforms where logical and pixel sizes differ

setVSyncEnabled(...) only switches the runtime swapchain present mode. It does not save settings; callers that expose a user setting must persist the requested value through SettingsManager.

Related Docs