Detect Double Clicks in SDL

Detecting double clicks in SDL involves checking the clicks member of the SDL_MouseButtonEvent structure.

This member indicates the number of times the mouse button was clicked in quick succession. A value of 2 in the clicks member signifies a double click.

Here’s a basic example of detecting double clicks:

1#include <SDL.h>
2
3#include <iostream>
4
5void HandleMouseButton(
6  const SDL_MouseButtonEvent& buttonEvent) {
7  if (buttonEvent.clicks == 2) {
8    std::cout << "Double Click Detected\n";  
9  }
10}
11
12int main(int argc, char* argv[]) {
13  if (SDL_Init(SDL_INIT_VIDEO) != 0) {
14    std::cerr << "SDL_Init Error: "
15      << SDL_GetError() << '\n';
16    return 1;
17  }
18
19  SDL_Window* window = SDL_CreateWindow(
20    "Double Click Detection",
21    100, 100, 640, 480,
22    SDL_WINDOW_SHOWN
23  );
24
25  if (window == nullptr) {
26    std::cerr << "SDL_CreateWindow Error: "
27      << SDL_GetError() << '\n';
28    SDL_Quit();
29    return 1;
30  }
31
32  SDL_Event event;
33  bool running = true;
34  while (running) {
35    while (SDL_PollEvent(&event)) {
36      if (event.type == SDL_QUIT) {
37        running = false;
38      } else if (event.type == SDL_MOUSEBUTTONDOWN) {
39        HandleMouseButton(event.button);
40      }
41    }
42  }
43
44  SDL_DestroyWindow(window);
45  SDL_Quit();
46  return 0;
47}

1Double Click Detected

How It Works

1. Event Loop: The main event loop calls SDL_PollEvent() to retrieve events.
2. Mouse Button Down: When a SDL_MOUSEBUTTONDOWN event is detected, it calls the HandleMouseButton() function.
3. Double Click Detection: Inside HandleMouseButton(), the clicks member of the SDL_MouseButtonEvent structure is checked. If clicks == 2, a double click is detected.

Points to Note

• Timing: The detection of double clicks relies on the system’s double-click time setting. SDL respects the user’s operating system settings for double-click speed, making it more reliable than implementing custom timing logic.
• State: The clicks member is present in both SDL_MOUSEBUTTONDOWN and SDL_MOUSEBUTTONUP events. Ensure you handle the event you care about.

Example Enhancement

You might also want to distinguish between single and double clicks or handle specific mouse buttons:

1void HandleMouseButton(
2  const SDL_MouseButtonEvent& buttonEvent) {
3  if (buttonEvent.clicks == 2) {
4    if (buttonEvent.button == SDL_BUTTON_LEFT) {
5      std::cout << "Left Button Double Click\n";  
6    }
7  } else {
8    if (buttonEvent.button == SDL_BUTTON_LEFT) {
9      std::cout << "Left Button Single Click\n";  
10    }
11  }
12}

1Left Button Double Click
2Left Button Single Click

This code checks which button was clicked and whether it was a single or double click. Using SDL’s built-in double-click detection is preferred over custom logic because it respects user settings and provides accurate results.