Handling Different Screen Resolutions in SDL2

Handling different screen resolutions is crucial for creating a game that looks good on various devices. Here's a strategy you can use:

First, decide on a base resolution for your game. This is the resolution you'll use for designing your game's layout and assets. For example, let's say we choose 1280x720 as our base resolution.

When your game starts, calculate a scaling factor based on the actual screen resolution:

1#include <SDL.h>
2#include <iostream>
3
4int main() {
5  SDL_Init(SDL_INIT_VIDEO);
6
7  SDL_DisplayMode dm;
8  if (SDL_GetCurrentDisplayMode(0, &dm) != 0) {
9    std::cout <<
10      "SDL_GetCurrentDisplayMode failed: " <<
11      SDL_GetError() << "\n";
12    return 1;
13  }
14
15  const int BASE_WIDTH = 1280;
16  const int BASE_HEIGHT = 720;
17  float scaleX = dm.w / static_cast<float>(
18    BASE_WIDTH);
19  float scaleY = dm.h / static_cast<float>(
20    BASE_HEIGHT);
21  float scale = std::min(scaleX, scaleY);
22
23  std::cout << "Screen resolution: " << dm.w <<
24    "x" << dm.h << "\n";
25  std::cout << "Scaling factor: " << scale <<
26    "\n";
27
28  SDL_Quit();
29  return 0;
30}

Use this scaling factor when rendering your game elements. You can create a utility function to scale positions and sizes:

1SDL_Rect ScaleRect(const SDL_Rect& rect,
2                   float scale) {
3  return SDL_Rect{
4    static_cast<int>(rect.x * scale),
5    static_cast<int>(rect.y * scale),
6    static_cast<int>(rect.w * scale),
7    static_cast<int>(rect.h * scale)};
8}

Create your SDL window at the native screen resolution, but render your game elements using the scaled positions and sizes:

1SDL_Window* window =
2  SDL_CreateWindow("Game",
3                   SDL_WINDOWPOS_UNDEFINED,
4                   SDL_WINDOWPOS_UNDEFINED,
5                   dm.w, dm.h,
6                   SDL_WINDOW_FULLSCREEN);
7
8// In your render loop:
9SDL_Rect baseRect{100, 100, 200, 200};
10SDL_Rect scaledRect =
11  ScaleRect(baseRect, scale);
12SDL_RenderFillRect(renderer, &scaledRect);

By following this approach, your game will maintain its relative layout across different screen resolutions while taking advantage of the full screen real estate available.