From b664e0102f343931756504f961f89a5705d45033 Mon Sep 17 00:00:00 2001
From: Persune <gumball2415@gmail.com>
Date: Wed, 18 Jan 2023 16:17:24 +0800
Subject: [PATCH] Keep non-LUT generation; use #elif

---
 crt_core.c |  4 ++--
 crt_nes.c  | 49 ++++++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 50 insertions(+), 3 deletions(-)

diff --git a/crt_core.c b/crt_core.c
index 8295b1c..9d4b139 100644
--- a/crt_core.c
+++ b/crt_core.c
@@ -108,11 +108,11 @@ eqf(struct EQF *f, int s)
     /* index : 0 1 2 3 4 5 6 */
     /* weight: 1 4 7 8 7 4 1 */
     return (s + h[6] + ((h[1] + h[5]) * 4) + ((h[2] + h[4]) * 7) + (h[3] * 8)) >> 5;
-#elseif USE_6_SAMPLE
+#elif USE_6_SAMPLE
     /* index : 0 1 2 3 4 5 */
     /* weight: 1 3 4 4 3 1 */
     return (s + h[5] + 3 * (h[1] + h[4]) + 4 * (h[2] + h[3])) >> 4;
-#elseif USE_5_SAMPLE
+#elif USE_5_SAMPLE
     /* index : 0 1 2 3 4 */
     /* weight: 1 2 2 2 1 */
     return (s + h[4] + ((h[1] + h[2] + h[3]) << 1)) >> 3;
diff --git a/crt_nes.c b/crt_nes.c
index fd9c689..21816d7 100644
--- a/crt_nes.c
+++ b/crt_nes.c
@@ -17,10 +17,13 @@
 #include <stdlib.h>
 #include <string.h>
 
+#define USE_LUT 0
+
+#if USE_LUT
 // Precalculate the low and high signal chosen for each 64 base colors
 // with their respective attenuated values
 // https://www.nesdev.org/wiki/NTSC_video#Brightness_Levels
-const int8_t IRE_levels[2][2][0x40]{
+const int IRE_levels[2][2][0x40]{
    // waveform low
    {
       // normal
@@ -94,6 +97,50 @@ square_sample(int p, int phase)
 
     return IRE_levels[v][e][p & 0x3F];
 }
+#else
+/* generate the square wave for a given 9-bit pixel and phase */
+static int
+square_sample(int p, int phase)
+{
+    static int active[6] = {
+        0300, 0100,
+        0500, 0400,
+        0600, 0200
+    };
+    int bri, hue, v;
+
+    hue = (p & 0x0f);
+    
+    /* last two columns are black */
+    if (hue >= 0x0e) {
+        return 0;
+    }
+
+    bri = ((p & 0x30) >> 4) * 300;
+    
+    switch (hue) {
+        case 0:
+            v = bri + 410;
+            break;
+        case 0x0d:
+            v = bri - 300;
+            break;
+        default:
+            v = (((hue + phase) % 12) < 6) ? (bri + 410) : (bri - 300);
+            break;
+    }
+
+    if (v > 1024) {
+        v = 1024;
+    }
+    /* red 0100, green 0200, blue 0400 */
+    if ((p & 0700) & active[(phase >> 1) % 6]) {
+        return (v >> 1) + (v >> 2);
+    }
+
+    return v;
+}
+#endif
 
 #define NES_OPTIMIZED 0