From dbbeddecb55c7bd5ca5239f0c040886cde7e29d7 Mon Sep 17 00:00:00 2001
From: Jaakko Keränen <jaakko.keranen@iki.fi>
Date: Fri, 7 Jan 2022 17:07:31 +0200
Subject: App: Optimizing periodic events

IssueID #416
---
 src/app.c      | 12 ++++--------
 src/app.h      |  1 +
 src/periodic.c | 25 +++++++++++++++++++++++++
 src/periodic.h |  1 +
 4 files changed, 31 insertions(+), 8 deletions(-)

diff --git a/src/app.c b/src/app.c
index 1a24e86c..0a17a665 100644
--- a/src/app.c
+++ b/src/app.c
@@ -1237,9 +1237,6 @@ iBool findCachedContent_App(const iString *url, iString *mime_out, iBlock *data_
 #endif
 
 iLocalDef iBool isWaitingAllowed_App_(iApp *d) {
-    if (!isEmpty_Periodic(&d->periodic)) {
-        return iFalse;
-    }
     if (d->warmupFrames > 0) {
         return iFalse;
     }
@@ -1253,10 +1250,6 @@ iLocalDef iBool isWaitingAllowed_App_(iApp *d) {
 
 static iBool nextEvent_App_(iApp *d, enum iAppEventMode eventMode, SDL_Event *event) {
     if (eventMode == waitForNewEvents_AppEventMode && isWaitingAllowed_App_(d)) {
-        /* If there are periodic commands pending, wait only for a short while. */
-        if (!isEmpty_Periodic(&d->periodic)) {
-            return SDL_WaitEventTimeout(event, 500);
-        }
         /* We may be allowed to block here until an event comes in. */
         if (isWaitingAllowed_App_(d)) {
             return SDL_WaitEvent(event);
@@ -1348,6 +1341,10 @@ void processEvents_App(enum iAppEventMode eventMode) {
                 break;
             }
             default: {
+                if (ev.type == SDL_USEREVENT && ev.user.code == periodic_UserEventCode) {
+                    dispatchCommands_Periodic(&d->periodic);
+                    continue;
+                }
 #if defined (LAGRANGE_ENABLE_IDLE_SLEEP)
                 if (ev.type == SDL_USEREVENT && ev.user.code == asleep_UserEventCode) {
                     if (SDL_GetTicks() - d->lastEventTime > idleThreshold_App_ &&
@@ -1580,7 +1577,6 @@ static int run_App_(iApp *d) {
     SDL_AddEventWatch(resizeWatcher_, d); /* redraw window during resizing */
 #endif
     while (d->isRunning) {
-        dispatchCommands_Periodic(&d->periodic);
         processEvents_App(waitForNewEvents_AppEventMode);
         runTickers_App_(d);
         refresh_App();
diff --git a/src/app.h b/src/app.h
index d15e1f21..5968de0d 100644
--- a/src/app.h
+++ b/src/app.h
@@ -61,6 +61,7 @@ enum iUserEventCode {
     command_UserEventCode = 1,
     refresh_UserEventCode,
     asleep_UserEventCode,
+    periodic_UserEventCode,
     /* The start of a potential touch tap event is notified via a custom event because
        sending SDL_MOUSEBUTTONDOWN would be premature: we don't know how long the tap will
        take, it could turn into a tap-and-hold for example. */
diff --git a/src/periodic.c b/src/periodic.c
index c65c8b07..b4f51ed3 100644
--- a/src/periodic.c
+++ b/src/periodic.c
@@ -57,6 +57,25 @@ iDefineTypeConstructionArgs(PeriodicCommand, (iAny *ctx, const char *cmd), ctx,
 
 static const uint32_t postingInterval_Periodic_ = 500;
 
+static uint32_t postEvent_Periodic_(uint32_t interval, void *context) {
+    iUnused(context);
+    SDL_UserEvent ev = { .type      = SDL_USEREVENT,
+                         .timestamp = SDL_GetTicks(),
+                         .code      = periodic_UserEventCode };
+    SDL_PushEvent((SDL_Event *) &ev);
+    return interval;
+}
+
+static void startOrStopWakeupTimer_Periodic_(iPeriodic *d, iBool start) {
+    if (start && !d->wakeupTimer) {
+        d->wakeupTimer = SDL_AddTimer(postingInterval_Periodic_, postEvent_Periodic_, d);
+    }
+    else if (!start && d->wakeupTimer) {
+        SDL_RemoveTimer(d->wakeupTimer);
+        d->wakeupTimer = 0;
+    }
+}
+
 static void removePending_Periodic_(iPeriodic *d) {
     iForEach(PtrSet, i, &d->pendingRemoval) {
         size_t pos;
@@ -68,6 +87,9 @@ static void removePending_Periodic_(iPeriodic *d) {
         }
     }
     clear_PtrSet(&d->pendingRemoval);
+    if (isEmpty_SortedArray(&d->commands)) {
+        startOrStopWakeupTimer_Periodic_(d, iFalse);
+    }
 }
 
 static iBool isDispatching_;
@@ -109,9 +131,11 @@ void init_Periodic(iPeriodic *d) {
     init_SortedArray(&d->commands, sizeof(iPeriodicCommand), cmp_PeriodicCommand_);
     d->lastPostTime = 0;
     init_PtrSet(&d->pendingRemoval);
+    d->wakeupTimer = 0;
 }
 
 void deinit_Periodic(iPeriodic *d) {
+    startOrStopWakeupTimer_Periodic_(d, iFalse);
     deinit_PtrSet(&d->pendingRemoval);
     iForEach(Array, i, &d->commands.values) {
         deinit_PeriodicCommand(i.value);
@@ -134,6 +158,7 @@ void add_Periodic(iPeriodic *d, iAny *context, const char *command) {
         init_PeriodicCommand(&pc, context, command);
         insert_SortedArray(&d->commands, &pc);
     }
+    startOrStopWakeupTimer_Periodic_(d, iTrue);
     unlock_Mutex(d->mutex);
 }
 
diff --git a/src/periodic.h b/src/periodic.h
index a56310a8..f65a4299 100644
--- a/src/periodic.h
+++ b/src/periodic.h
@@ -35,6 +35,7 @@ struct Impl_Periodic {
     iSortedArray commands;
     uint32_t     lastPostTime;
     iPtrSet      pendingRemoval; /* contexts */
+    int          wakeupTimer; /* running while there are pending periodic commands */
 };
 
 void    init_Periodic   (iPeriodic *);
-- 
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