From e254c99b38713303970526514f6ade21a2956faf Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <[EMAIL REDACTED]>
Date: Mon, 14 Oct 2024 23:16:02 -0400
Subject: [PATCH] examples/game/01-snake: Update game logic in AppIterate,
don't use a timer.
Reference Issue #11210.
---
examples/game/01-snake/snake.c | 37 +++++++++++++---------------------
1 file changed, 14 insertions(+), 23 deletions(-)
diff --git a/examples/game/01-snake/snake.c b/examples/game/01-snake/snake.c
index 8257e416d2f0e..f1be83c4a34eb 100644
--- a/examples/game/01-snake/snake.c
+++ b/examples/game/01-snake/snake.c
@@ -57,8 +57,8 @@ typedef struct
{
SDL_Window *window;
SDL_Renderer *renderer;
- SDL_TimerID step_timer;
SnakeContext snake_ctx;
+ Uint64 last_step;
} AppState;
SnakeCell snake_cell_at(const SnakeContext *ctx, char x, char y)
@@ -208,16 +208,6 @@ void snake_step(SnakeContext *ctx)
}
}
-static Uint32 sdl_timer_callback_(void *payload, SDL_TimerID timer_id, Uint32 interval)
-{
- /* NOTE: snake_step is not called here directly for multithreaded concerns. */
- SDL_Event event;
- SDL_zero(event);
- event.type = SDL_EVENT_USER;
- SDL_PushEvent(&event);
- return interval;
-}
-
static int handle_key_event_(SnakeContext *ctx, SDL_Scancode key_code)
{
switch (key_code) {
@@ -250,14 +240,22 @@ static int handle_key_event_(SnakeContext *ctx, SDL_Scancode key_code)
SDL_AppResult SDL_AppIterate(void *appstate)
{
- AppState *as;
- SnakeContext *ctx;
+ AppState *as = (AppState *)appstate;
+ SnakeContext *ctx = &as->snake_ctx;
+ const Uint64 now = SDL_GetTicks();
SDL_FRect r;
unsigned i;
unsigned j;
int ct;
- as = (AppState *)appstate;
- ctx = &as->snake_ctx;
+
+ // run game logic if we're at or past the time to run it.
+ // if we're _really_ behind the time to run it, run it
+ // several times.
+ while ((now - as->last_step) >= STEP_RATE_IN_MILLISECONDS) {
+ snake_step(ctx);
+ as->last_step += STEP_RATE_IN_MILLISECONDS;
+ }
+
r.w = r.h = SNAKE_BLOCK_SIZE_IN_PIXELS;
SDL_SetRenderDrawColor(as->renderer, 0, 0, 0, 255);
SDL_RenderClear(as->renderer);
@@ -321,10 +319,7 @@ SDL_AppResult SDL_AppInit(void **appstate, int argc, char *argv[])
snake_initialize(&as->snake_ctx);
- as->step_timer = SDL_AddTimer(STEP_RATE_IN_MILLISECONDS, sdl_timer_callback_, NULL);
- if (as->step_timer == 0) {
- return SDL_APP_FAILURE;
- }
+ as->last_step = SDL_GetTicks();
return SDL_APP_CONTINUE;
}
@@ -335,9 +330,6 @@ SDL_AppResult SDL_AppEvent(void *appstate, SDL_Event *event)
switch (event->type) {
case SDL_EVENT_QUIT:
return SDL_APP_SUCCESS;
- case SDL_EVENT_USER:
- snake_step(ctx);
- break;
case SDL_EVENT_KEY_DOWN:
return handle_key_event_(ctx, event->key.scancode);
}
@@ -348,7 +340,6 @@ void SDL_AppQuit(void *appstate, SDL_AppResult result)
{
if (appstate != NULL) {
AppState *as = (AppState *)appstate;
- SDL_RemoveTimer(as->step_timer);
SDL_DestroyRenderer(as->renderer);
SDL_DestroyWindow(as->window);
SDL_free(as);