Using SDL_PushEvent for Event Reporting

In our Minesweeper game, we use SDL_PushEvent() to report events like bomb placement or cell clearing.

This approach might seem more complicated than directly calling a function, but it offers several benefits that align well with game development practices. Let's explore why we chose this method and how it compares to direct function calls.

Event-Driven Architecture

Using SDL_PushEvent() allows us to implement an event-driven architecture. In this paradigm, different parts of our game can communicate without being tightly coupled. Here's a simple example of how we might use it in our Minesweeper cell:

1#include <SDL.h>
2#include <iostream>
3
4namespace UserEvents {
5  inline Uint32 BOMB_PLACED =
6    SDL_RegisterEvents(1);
7}
8
9class MinesweeperCell {
10public:
11  void PlaceBomb() {
12    // Place the bomb logic here
13    ReportEvent(UserEvents::BOMB_PLACED);
14  }
15
16private:
17  void ReportEvent(Uint32 EventType) {
18    SDL_Event event{EventType};
19    event.user.data1 = this;
20    SDL_PushEvent(&event);
21  }
22};
23
24void HandleSDLEvents() {
25  SDL_Event event;
26  while (SDL_PollEvent(&event)) {
27    if (event.type == UserEvents::BOMB_PLACED) {
28      std::cout << "A bomb was placed!\n";
29    }
30  }
31}
32
33int main() {
34  if (SDL_Init(SDL_INIT_EVENTS) < 0) {
35    std::cerr << "SDL initialization failed\n";
36    return 1;
37  }
38
39  MinesweeperCell cell;
40  cell.PlaceBomb();
41
42  HandleSDLEvents();
43
44  SDL_Quit();
45  return 0;
46}

This code demonstrates how we can push a custom event when a bomb is placed, and then handle it in our main event loop.

Benefits of Using SDL_PushEvent()

1. Decoupling: The cell doesn't need to know who's interested in bomb placement. Any part of the game can listen for and react to these events.
2. Centralized Event Handling: All events, including SDL's built-in events and our custom ones, can be processed in a single loop.
3. Asynchronous Communication: Events are queued and can be processed when the game is ready, not immediately when they occur.
4. Consistency with SDL: By using SDL's event system, we're consistent with how SDL handles other events like keyboard or mouse input.

Comparison with Direct Function Calls

Let's compare this to a direct function call approach:

1#include <iostream>
2
3class MinesweeperGrid {
4public:
5  void OnBombPlaced() {
6    std::cout << "A bomb was placed!\n";
7  }
8};
9
10class MinesweeperCell {
11public:
12  MinesweeperCell(MinesweeperGrid *grid) :
13      grid(grid) {}
14
15  void PlaceBomb() {
16    // Place the bomb logic here
17    grid->OnBombPlaced();
18  }
19
20private:
21  MinesweeperGrid *grid;
22};
23
24int main() {
25  MinesweeperGrid grid;
26  MinesweeperCell cell(&grid);
27  cell.PlaceBomb();
28  return 0;
29}

While this is simpler, it has drawbacks:

• The cell needs to know about the grid, creating tighter coupling.
• We can't easily handle the bomb placement asynchronously or in a central event loop.
• It's harder to add new listeners without modifying the MinesweeperCell class.

By using SDL_PushEvent(), we create a more flexible, scalable architecture for our Minesweeper game, which will be beneficial as we add more features and complexity.