Events vs State for Mouse Input

The choice between using events and state checking for mouse input depends on your specific needs. Let's explore the key differences.

An event-based approach might look something like this:

1#include <SDL.h>
2#include <iostream>
3#include "Window.h"
4
5void HandleMouseEvent(SDL_Event& E) {
6  if (E.type == SDL_MOUSEMOTION) {
7    std::cout << "\nMouse moved to: ("
8      << E.motion.x << ", " << E.motion.y;
9  } else if (E.type == SDL_MOUSEBUTTONDOWN) {
10    std::cout << "\nButton pressed at: ("
11      << E.button.x << ", " << E.button.y;
12  }
13}
14
15int main(int argc, char** argv) {
16  SDL_Init(SDL_INIT_VIDEO);
17  Window GameWindow;
18  SDL_Event E;
19
20  while (true) {
21    while (SDL_PollEvent(&E)) {
22      HandleMouseEvent(E);
23    }
24    GameWindow.Update();
25  }
26
27  SDL_Quit();
28  return 0;
29}

1Mouse moved to: 110, 102
2Mouse moved to: 111, 102
3Button pressed at: 111, 102
4Mouse moved to: 106, 102

Implementing the same functionality using a state-based approach could look like this

1#include <SDL.h>
2#include <iostream>
3#include "Window.h"
4
5void CheckMouseState() {
6  int x, y;
7  Uint32 Buttons = SDL_GetMouseState(&x, &y);  
8
9  std::cout << "Current mouse state - Position:"
10    " (" << x << ", " << y << ") ";
11
12  if (Buttons & SDL_BUTTON_LMASK) {
13    std::cout << "Left button pressed";
14  }
15  std::cout << "\n";
16}
17
18int main(int argc, char** argv) {
19  SDL_Init(SDL_INIT_VIDEO);
20  Window GameWindow;
21  SDL_Event E;
22
23  while (true) {
24    while (SDL_PollEvent(&E)) {
25      // Handle other events...
26    }
27
28    CheckMouseState();  
29    GameWindow.Update();
30  }
31
32  SDL_Quit();
33  return 0;
34}

1Current mouse state - Position (0, 43)
2Current mouse state - Position (1, 43)
3Current mouse state - Position (1, 44) Left Button Pressed
4Current mouse state - Position (1, 44) Left Button Pressed

Timing

• Events tell you WHEN something happened
• State tells you WHAT is happening right now

Data Capture

• Events capture every change (movement, clicks)
• State only gives you the current situation when you check

Use Cases

Events are better for:

• UI interactions (clicks, hover effects)
• Precise movement tracking
• Responding to specific actions

State is better for:

• Continuous tracking (drag operations)
• Regular polling (cursor following)
• Checking conditions during other events

Performance

• Events generate data for every change
• State checking only uses resources when you explicitly check

Choose events when you need to know about every change, and state checking when you just need to know the current situation at specific times.