From 11fe11568e27e5fc7d5d58ee64cb83b185240daf Mon Sep 17 00:00:00 2001
From: Paul Duncan <pabs@pablotron.org>
Date: Wed, 16 Jan 2019 08:36:29 -0500
Subject: limit step events to 100ms

---
 src/sdl/solve.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/src/sdl/solve.c b/src/sdl/solve.c
index 0fee274..a3e27e8 100644
--- a/src/sdl/solve.c
+++ b/src/sdl/solve.c
@@ -11,6 +11,7 @@ struct solve_t_ {
   // thread-private copy of context
   sok_ctx_t ctx;
 
+  // event type for custom SDL SOLVE_* events
   Uint32 solve_event_type;
 
   // number of moves at call to solve()
@@ -18,6 +19,9 @@ struct solve_t_ {
 
   // number of times the on_step cb has been invoked
   size_t num_steps;
+
+  // last time the SOLVE_EVENT_STEP event was pushed
+  Uint32 last_step_event_ticks;
   
   // result of solve
   bool result;
@@ -65,7 +69,6 @@ solve_on_step(
   data->num_steps++;
 
   // cache number of steps and cancel state
-  const size_t num_steps = data->num_steps;
   const bool cancel = data->cancel;
 
   // unlock mutex
@@ -73,7 +76,15 @@ solve_on_step(
     die("SDL_UnlockMutex(): %s", SDL_GetError());
   }
 
-  if ((num_steps % 100) == 0) {
+  // get timestamp and next update timestamp
+  const Uint32 ticks = SDL_GetTicks(),
+               next_step_ticks = data->last_step_event_ticks + 100;
+
+  // limit step events to every 100ms
+  if (SDL_TICKS_PASSED(ticks, next_step_ticks)) {
+    // cache timestamp
+    data->last_step_event_ticks = ticks;
+
     // push event
     push_event(data, SOLVE_EVENT_STEP, NULL);
   }
@@ -140,6 +151,7 @@ solve(
   data->solve_event_type = solve_event_type;
   data->old_num_moves = ctx->num_moves;
   data->num_steps = 0;
+  data->last_step_event_ticks = SDL_GetTicks();
   data->result = false;
   data->cancel = false;
 
-- 
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