From 18d4d36065048a1c61b4b8a5cfc3a7a64737d832 Mon Sep 17 00:00:00 2001
From: Thomas Voss <mail@thomasvoss.com>
Date: Sat, 17 Feb 2024 00:31:48 +0100
Subject: Optimize redrawing

---
 src/ahoy/emulator.c | 3 ++-
 src/ahoy/emulator.h | 1 +
 src/ahoy/gui.c      | 9 ++++++++-
 src/ahoy/gui.h      | 2 +-
 src/ahoy/main.c     | 5 +++--
 5 files changed, 15 insertions(+), 5 deletions(-)

(limited to 'src')

diff --git a/src/ahoy/emulator.c b/src/ahoy/emulator.c
index d240fbc..980a0a7 100644
--- a/src/ahoy/emulator.c
+++ b/src/ahoy/emulator.c
@@ -80,6 +80,7 @@ opexec(uint16_t op)
 	case 0x0:
 		switch (op) {
 		case 0x00E0:
+			c8.needs_redraw = true;
 			memset(c8.screen, 0, sizeof(c8.screen));
 			break;
 		case 0x00EE:
@@ -211,9 +212,9 @@ opexec(uint16_t op)
 		unsigned y = (op & 0x00F0) >> 4;
 		unsigned n = (op & 0x000F) >> 0;
 
+		c8.needs_redraw = true;
 		if (c8.I + n > lengthof(mem))
 			diex("%s: attempted to draw sprite beyond bounds of RAM", filename);
-
 		for (unsigned i = 0; i < n; i++) {
 			uint8_t spr_row = mem[c8.I + i];
 			uint8_t scr_row = c8.V[y] + i;
diff --git a/src/ahoy/emulator.h b/src/ahoy/emulator.h
index 69438db..24aa8ce 100644
--- a/src/ahoy/emulator.h
+++ b/src/ahoy/emulator.h
@@ -15,6 +15,7 @@
    I  — register to hold addresses
    */
 struct chip8 {
+	bool needs_redraw;
 	bool kbd[16];
 	uint8_t V[16];
 	uint8_t DT, ST, SP;
diff --git a/src/ahoy/gui.c b/src/ahoy/gui.c
index 1933849..d7514e9 100644
--- a/src/ahoy/gui.c
+++ b/src/ahoy/gui.c
@@ -82,6 +82,7 @@ windrw(void)
 	r.w = (qw = div(sw, SCR_WDTH)).quot;
 	r.h = (qh = div(sh, SCR_HIGH)).quot;
 
+	c8.needs_redraw = false;
 	SDL_SetRenderDrawColor(rndr, 0, 0, 0, UINT8_MAX);
 	SDL_RenderClear(rndr);
 
@@ -119,7 +120,7 @@ auplay(bool stop)
 }
 
 void
-readkb(void)
+readevnt(void)
 {
 	SDL_Event e;
 
@@ -129,6 +130,12 @@ readkb(void)
 			estate = ES_STOP;
 			break;
 
+		case SDL_WINDOWEVENT:
+			/* For some reason checking for SDL_WINDOWEVENT_RESIZE and friends
+			   doesn’t work, so just catch all window events */
+			c8.needs_redraw = true;
+			break;
+
 		case SDL_KEYDOWN:
 			switch (e.key.keysym.sym) {
 			case SDLK_SPACE:
diff --git a/src/ahoy/gui.h b/src/ahoy/gui.h
index 0760437..220bcb1 100644
--- a/src/ahoy/gui.h
+++ b/src/ahoy/gui.h
@@ -15,7 +15,7 @@ void wininit(void);
 void winfree(void);
 void windrw(void);
 void auplay(bool);
-void readkb(void);
+void readevnt(void);
 
 extern emustate estate;
 
diff --git a/src/ahoy/main.c b/src/ahoy/main.c
index 467b1fa..e47598c 100644
--- a/src/ahoy/main.c
+++ b/src/ahoy/main.c
@@ -189,7 +189,7 @@ reset:
 		double dt;
 		uint64_t st, et;
 
-		readkb();
+		readevnt();
 		if (estate == ES_PAUSED)
 			continue;
 		if (estate == ES_RESET) {
@@ -204,7 +204,8 @@ reset:
 		dt = (double)((et - st) * 1000) / SDL_GetPerformanceFrequency();
 		SDL_Delay(16.67f > dt ? 16.67f - dt : 0);
 
-		windrw();
+		if (c8.needs_redraw)
+			windrw();
 
 		if (c8.DT > 0)
 			c8.DT--;
-- 
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