Rendering Text with SDL_ttf

Text Rendering Performance

What's the performance impact of rendering text every frame vs. caching text surfaces?

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Rendering text every frame versus caching text surfaces can have a significant impact on performance, especially in applications with lots of text or limited processing power. Let's break down the two approaches:

Rendering text every frame:

  • Pros: Flexibility for dynamic text that changes frequently.
  • Cons: High CPU usage, potential frame rate drops.

Caching text surfaces:

  • Pros: Better performance, reduced CPU usage.
  • Cons: Higher memory usage, potential complexity for managing cached surfaces.

In general, caching text surfaces is more performant. Here's a simple example to illustrate the difference:

#include <SDL.h>
#include <SDL_ttf.h>

class Text {
public:
  Text(TTF_Font* font, const char* text,
       SDL_Color color) {
    surface = TTF_RenderText_Blended(
      font, text, color);
  }

  void render(SDL_Surface* dest, int x, int y) {
    SDL_Rect dstRect = {x, y, 0, 0};
    SDL_BlitSurface(surface, nullptr, dest,
                    &dstRect);
  }

  ~Text() { SDL_FreeSurface(surface); }

private:
  SDL_Surface* surface;
};

// Usage
Text cachedText(font, "Hello, World!",
                {255, 255, 255, 255});

// In render loop
cachedText.render(
  screenSurface, 100, 100);

This cached approach is much faster than rendering the text every frame:

// In render loop (slower)
SDL_Surface* textSurface =
  TTF_RenderText_Blended(font, "Hello, World!",
                         {255, 255, 255, 255});
SDL_BlitSurface(textSurface, nullptr,
                screenSurface, &dstRect);
SDL_FreeSurface (textSurface);

For optimal performance, cache static text and only re-render when the text content changes.

Answers to questions are automatically generated and may not have been reviewed.

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