How do I create a resizable window in SDL?

Question

Ryan McCombe · Accepted Answer

To create a resizable window in SDL, you need to use the SDL_WINDOW_RESIZABLE flag when you call the SDL_CreateWindow() function. This flag allows the window to be resized by the user after it has been created.

Here's a simple example to demonstrate how to create a resizable window in SDL:

1#include <SDL.h>
2
3class Window {
4public:
5  Window() {
6    SDL_Init(SDL_INIT_VIDEO);
7
8    SDLWindow = SDL_CreateWindow(
9      "Resizable Window",
10      100, 100, 800, 600,
11      SDL_WINDOW_RESIZABLE 
12    );
13  }
14
15  ~Window() {
16    SDL_DestroyWindow(SDLWindow);
17    SDL_Quit();
18  }
19
20  SDL_Window* SDLWindow{nullptr};
21};
22
23int main(int argc, char** argv) {
24  Window GameWindow;
25  SDL_Event Event;
26
27  while (true) {
28    while (SDL_PollEvent(&Event)) {
29      if (Event.type == SDL_QUIT) {
30        return 0;
31      }
32    }
33  }
34  
35  return 0;
36}

In this example, we create a window titled "Resizable Window" with a size of 800x600 pixels. The SDL_WINDOW_RESIZABLE flag makes the window resizable.

Combining Flags

You can combine the SDL_WINDOW_RESIZABLE flag with other window flags using the bitwise OR operator (|). For example, to create a window that is both resizable and has input focus, you can do the following:

1SDLWindow = SDL_CreateWindow(
2  "Resizable and Focused Window",
3  100, 100, 800, 600,
4  SDL_WINDOW_RESIZABLE | SDL_WINDOW_INPUT_FOCUS 
5);

Handling Resize Events

To handle the window resize events, you can check for SDL_WINDOWEVENT_RESIZED in your event loop. Here's an example:

1#include <SDL.h>
2#include <iostream>
3#include "Window.h"
4
5void HandleWindowEvent(SDL_WindowEvent& E) {
6  if (E.event == SDL_WINDOWEVENT_RESIZED) {
7    std::cout << "Window resized to "
8      << E.data1 << "x" << E.data2 << "\n";  
9  }
10}
11
12int main(int argc, char** argv) {
13  Window GameWindow;
14  SDL_Event Event;
15
16  while (true) {
17    while (SDL_PollEvent(&Event)) {
18      if (Event.type == SDL_QUIT) {
19        return 0;
20      }
21      if (Event.type == SDL_WINDOWEVENT) {
22        HandleWindowEvent(Event.window);
23      }
24    }
25  }
26  
27  return 0;
28}

This code will output the new dimensions of the window whenever it is resized. Handling resize events is important for updating your game's rendering logic to fit the new window size.

1Window resized to 1024x768

Creating resizable windows in SDL is straightforward and allows for more dynamic and user-friendly applications. Don't forget to handle resize events appropriately to ensure your application behaves as expected when the window size changes.

Managing Window Input Focus

Creating a Resizable Window in SDL

Combining Flags

Handling Resize Events

Managing Window Input Focus

Game Development with SDL2

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