Can I create a borderless window that still has a resizable frame?

Question

Ryan McCombe · Accepted Answer

Unfortunately, SDL2 does not natively support creating a borderless window with a resizable frame.

The SDL_WINDOW_BORDERLESS flag removes all decorations, including resize handles. The SDL_WINDOW_RESIZABLE flag, which allows resizing, only applies to windows with decorations.

If you need a resizable borderless window, you must implement the resizing functionality yourself by handling window resizing events (SDL_WINDOWEVENT_RESIZED) and manually adjusting the window size. You can also combine this with custom rendering to simulate resize handles.

Example of handling resize events:

1#include <SDL.h>
2#include <iostream>
3
4int main() {
5  SDL_Init(SDL_INIT_VIDEO);
6
7  SDL_Window* Window{SDL_CreateWindow(
8    "Resizable Borderless",
9    SDL_WINDOWPOS_CENTERED,
10    SDL_WINDOWPOS_CENTERED,
11    800, 600,
12    SDL_WINDOW_BORDERLESS 
13  )};
14
15  SDL_Event Event;
16  bool Running{true};
17  while (Running) {
18    while (SDL_PollEvent(&Event)) {
19      if (Event.type == SDL_QUIT) {
20        Running = false;
21      } else if (
22        Event.type == SDL_WINDOWEVENT &&
23        Event.window.event == SDL_WINDOWEVENT_RESIZED
24      ) {
25        int NewWidth = Event.window.data1;
26        int NewHeight = Event.window.data2;
27        std::cout << "Window resized to: "
28          << NewWidth << "x" << NewHeight << "\n";
29      }
30    }
31  }
32
33  SDL_DestroyWindow(Window);
34  SDL_Quit();
35}

1Window resized to: 1024x768

If resizing is critical, consider using platform-specific APIs to add custom resize handles. Another option is to use higher-level libraries like Dear ImGui that support customizable windowing.

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