From 6b35522c877cbb27282df776db8f08532d0441f5 Mon Sep 17 00:00:00 2001
From: Thomas Voss <mail@thomasvoss.com>
Date: Fri, 16 Feb 2024 23:59:08 +0100
Subject: Improve video drawing

---
 src/ahoy/config.h   |  1 +
 src/ahoy/emulator.c |  2 --
 src/ahoy/emulator.h |  1 -
 src/ahoy/gui.c      | 37 ++++++++++++++++++++++---------------
 src/ahoy/main.c     | 11 +++++++----
 5 files changed, 30 insertions(+), 22 deletions(-)

(limited to 'src')

diff --git a/src/ahoy/config.h b/src/ahoy/config.h
index 6fa60c2..15ad895 100644
--- a/src/ahoy/config.h
+++ b/src/ahoy/config.h
@@ -4,6 +4,7 @@
 #include <stdint.h>
 
 struct config {
+	bool scanls;
 	bool seeded;
 	uint16_t seed;
 	unsigned cpu_hz;
diff --git a/src/ahoy/emulator.c b/src/ahoy/emulator.c
index 79ff4dc..d240fbc 100644
--- a/src/ahoy/emulator.c
+++ b/src/ahoy/emulator.c
@@ -81,7 +81,6 @@ opexec(uint16_t op)
 		switch (op) {
 		case 0x00E0:
 			memset(c8.screen, 0, sizeof(c8.screen));
-			c8.needs_redraw = true;
 			break;
 		case 0x00EE:
 			if (c8.SP == 0)
@@ -228,7 +227,6 @@ opexec(uint16_t op)
 			c8.screen[scr_row] ^= msk;
 		}
 
-		c8.needs_redraw = true;
 		break;
 	}
 
diff --git a/src/ahoy/emulator.h b/src/ahoy/emulator.h
index 24aa8ce..69438db 100644
--- a/src/ahoy/emulator.h
+++ b/src/ahoy/emulator.h
@@ -15,7 +15,6 @@
    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 0997bf9..1933849 100644
--- a/src/ahoy/gui.c
+++ b/src/ahoy/gui.c
@@ -5,6 +5,7 @@
 #include <SDL.h>
 
 #include "cerr.h"
+#include "config.h"
 #include "emulator.h"
 #include "gui.h"
 #include "macros.h"
@@ -12,6 +13,7 @@
 #define SCR_SCALE 20
 #define SCR_WDTH  64
 #define SCR_HIGH  32
+#define SCNL_HGHT 2
 
 #define diesx(fmt) diex(fmt ": %s", SDL_GetError())
 
@@ -65,12 +67,9 @@ winfree(void)
 void
 windrw(void)
 {
-	SDL_Rect r = {
-		.x = 0,
-		.y = 0,
-		.w = SCR_SCALE,
-		.h = SCR_SCALE,
-	};
+	int sw, sh;
+	div_t qw, qh;
+	SDL_Rect r;
 	static const uint64_t cols[] = {
 		63, 62, 61, 60, 59, 58, 57, 56, 55, 54, 53, 52, 51, 50, 49, 48,
 		47, 46, 45, 44, 43, 42, 41, 40, 39, 38, 37, 36, 35, 34, 33, 32,
@@ -78,22 +77,19 @@ windrw(void)
 		15, 14, 13, 12, 11, 10, 9,  8,  7,  6,  5,  4,  3,  2,  1,  0,
 	};
 
-	c8.needs_redraw = false;
+	SDL_GetWindowSize(win, &sw, &sh);
+
+	r.w = (qw = div(sw, SCR_WDTH)).quot;
+	r.h = (qh = div(sh, SCR_HIGH)).quot;
 
-	for (size_t i = 0; i < lengthof(c8.screen); i++) {
-		if (c8.screen[i])
-			goto noclr;
-	}
 	SDL_SetRenderDrawColor(rndr, 0, 0, 0, UINT8_MAX);
 	SDL_RenderClear(rndr);
-	return;
 
-noclr:
 	for (size_t i = 0; i < lengthof(c8.screen); i++) {
 		for (size_t j = 64; j-- > 0;) {
 			bool set = (UINT64_C(1) << j) & c8.screen[i];
-			r.x = cols[j] * SCR_SCALE;
-			r.y = i * SCR_SCALE;
+			r.x = cols[j] * qw.quot + qw.rem / 2;
+			r.y = i * qh.quot + qh.rem / 2;
 			if (set)
 				SDL_SetRenderDrawColor(rndr, 0, UINT8_MAX, 0, UINT8_MAX);
 			else
@@ -102,6 +98,17 @@ noclr:
 		}
 	}
 
+	if (cfg.scanls) {
+		SDL_Rect r = {
+			.w = sw,
+			.h = SCNL_HGHT,
+		};
+
+		SDL_SetRenderDrawColor(rndr, 0, 0, 0, UINT8_MAX);
+		for (r.y = 0; r.y < sh; r.y += SCNL_HGHT * 2)
+			SDL_RenderFillRect(rndr, &r);
+	}
+
 	SDL_RenderPresent(rndr);
 }
 
diff --git a/src/ahoy/main.c b/src/ahoy/main.c
index b107fa2..467b1fa 100644
--- a/src/ahoy/main.c
+++ b/src/ahoy/main.c
@@ -59,7 +59,7 @@ void
 usage(void)
 {
 	fprintf(stderr,
-	        "Usage: %s [-c clock speed] [-s seed] [file]\n"
+	        "Usage: %s [-S] [-c clock speed] [-s seed] [file]\n"
 	        "       %s -h\n",
 	        argv0, argv0);
 	exit(EXIT_FAILURE);
@@ -89,13 +89,14 @@ main(int argc, char **argv)
 		{"clock-speed", required_argument, nullptr, 'c'},
 		{"help",        no_argument,       nullptr, 'h'},
 		{"seed",        required_argument, nullptr, 's'},
+		{"scanlines",   no_argument,       nullptr, 'S'},
 		{nullptr,       no_argument,       nullptr, 0  },
 	};
 
 	argv0 = argv[0];
 	cerrinit(*argv);
 
-	while ((opt = getopt_long(argc, argv, "c:hs:", longopts, nullptr)) != -1) {
+	while ((opt = getopt_long(argc, argv, "c:hs:S", longopts, nullptr)) != -1) {
 		switch (opt) {
 		case 'h':
 			execlp("man", "man", "1", argv[0], nullptr);
@@ -114,6 +115,9 @@ main(int argc, char **argv)
 			NUMERIC_ARG(uint16_t, UINT16_MAX, PRIu16, strtou16, seed, "seed");
 			cfg.seeded = true;
 			break;
+		case 'S':
+			cfg.scanls = true;
+			break;
 		default:
 			usage();
 		}
@@ -200,8 +204,7 @@ reset:
 		dt = (double)((et - st) * 1000) / SDL_GetPerformanceFrequency();
 		SDL_Delay(16.67f > dt ? 16.67f - dt : 0);
 
-		if (c8.needs_redraw)
-			windrw();
+		windrw();
 
 		if (c8.DT > 0)
 			c8.DT--;
-- 
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