From 0d3076fe40e1af0c5d56c57e3761cfb2f103cc6d Mon Sep 17 00:00:00 2001
From: Matthew Cather <mattbob4@gmail.com>
Date: Fri, 23 Aug 2024 17:25:21 -0500
Subject: [PATCH] Fix `clock` CPU utilization

No need to redraw if there has not been any events. Poll for
events about every 100 ms. Drops utilization from around 25% to
less than 0.

Also swap `-ffunction-sections -fdata-sections` for LTO to save
~5 Kb of memory when loaded and probably an immeasurable amount
of performance.
---
 src/clock/Makefile |  2 +-
 src/clock/main.c   | 11 ++++++++++-
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/src/clock/Makefile b/src/clock/Makefile
index 872129aba..db76398fd 100644
--- a/src/clock/Makefile
+++ b/src/clock/Makefile
@@ -4,7 +4,7 @@ include ../common/config.mk
 
 TARGET = clock
 LDFLAGS := $(LDFLAGS) -lSDL -lpthread -lmi_sys -lmi_gfx
-CFLAGS := $(CFLAGS) -I./font -Os -ffunction-sections -fdata-sections
+CFLAGS := $(CFLAGS) -I./font -Os -flto -fno-fat-lto-objects
 
 include ../common/commands.mk
 include ../common/recipes.mk
diff --git a/src/clock/main.c b/src/clock/main.c
index e7dfdf1e2..1275e50f6 100644
--- a/src/clock/main.c
+++ b/src/clock/main.c
@@ -39,6 +39,7 @@ SOFTWARE.
 #define MAX_SECOND 59
 #define MAX_MINUTE MAX_SECOND
 #define MAX_HOUR 23
+#define MS_TO_US(ms)  ms * 1000 
 
 SDL_Surface *sdl_screen, *screen;
 
@@ -207,9 +208,10 @@ int main(int argc, char *argv[])
                           &hour_selected, &minute_selected, &seconds_selected);
 
     SDL_EnableKeyRepeat(500, 50);
-
+    int dirty = 1; // first draw
     while (!quit) {
         while (SDL_PollEvent(&event)) {
+            dirty = 1;
             switch (event.type) {
             case SDL_KEYUP:
                 switch (event.key.keysym.sym) {
@@ -296,6 +298,11 @@ int main(int argc, char *argv[])
             }
         }
 
+        if (dirty != 1) {
+            usleep(MS_TO_US(100));
+            continue;
+        }
+
         Check_leap_year();
         Dont_go_over_days();
         Dont_go_over_hour();
@@ -330,6 +337,8 @@ int main(int argc, char *argv[])
 
         /* Flip the screen so it gets displayed*/
         GFX_Flip(screen);
+
+        dirty = 0;
     }
 
     /* Make sure to clean up the allocated surfaces before exiting.