From b54e5b66f1656bb99c6d246420c162bdc2be1c51 Mon Sep 17 00:00:00 2001
From: Carlos Sanchez <randomouscrap98@aol.com>
Date: Mon, 22 Jul 2024 21:23:21 -0400
Subject: [PATCH] Generic bit shift

---
 main.c | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/main.c b/main.c
index a225a08..897ceb1 100644
--- a/main.c
+++ b/main.c
@@ -12,6 +12,7 @@ typedef uint8_t u8;
 typedef int32_t i32;
 
 #define CDEPTH 255
+#define FIXEDPOINTDEPTH 8
 
 #define log(fmt, ...) fprintf(stderr, fmt "\n", ##__VA_ARGS__)
 #define panic(fmt, ...) { fprintf(stderr, "PANIC: " fmt "\n", ##__VA_ARGS__); exit(EXIT_FAILURE); }
@@ -57,10 +58,10 @@ void drawTexInto(struct texture tex, struct texture buffer, struct rect texbound
    // integers. By using 256, we are essentially adding 8 bits of "decimal
    // point". If you need more bits (or less), just change this to some other
    // power of 2. 
-   i32 stepx = 256 * (float)texwidth / outwidth;
-   i32 stepy = 256 * (float)texheight / outheight;
-   i32 texx = 256 * texbounds.x1;
-   i32 texy = 256 * texbounds.y1;
+   i32 stepx = (1 << FIXEDPOINTDEPTH) * (float)texwidth / outwidth;
+   i32 stepy = (1 << FIXEDPOINTDEPTH) * (float)texheight / outheight;
+   i32 texx = (1 << FIXEDPOINTDEPTH) * texbounds.x1;
+   i32 texy = (1 << FIXEDPOINTDEPTH) * texbounds.y1;
    //log("%f,%f step %f,%f", texx, texy, stepx, stepy);
    // Buffer is R G B for each pixel, then across then down. If you want X, Y,
    // it's: 3 * (x + y * width)
@@ -69,7 +70,7 @@ void drawTexInto(struct texture tex, struct texture buffer, struct rect texbound
       for(int x = bufbounds.x1; x < bufbounds.x2; x++) {
          // And then with the shift, it is log2(256), or whatever you shifted
          // by up there. So 512 would be 9, because 2^9 = 512
-         i32 texi = 3 * ((texx >> 8) + tex.width * (texy >> 8));
+         i32 texi = 3 * ((texx >> FIXEDPOINTDEPTH) + tex.width * (texy >> FIXEDPOINTDEPTH));
          i32 bufi = 3 * (x + y * buffer.width);
          memcpy(buffer.data + bufi, tex.data + texi, 3);
          texx += stepx;
@@ -99,8 +100,8 @@ int main() {
    };
 
    // We actually stretch a texture here
-   struct rect texrect = { 0, 0, 8, 12 };
-   struct rect bufrect = { 10, 10, 509, 499 };
+   struct rect texrect = { 0, 0, 16, 16 };
+   struct rect bufrect = { 10, 10, 212, 192};
 
    clock_t start = clock();
    for(int i = 0; i < 50; i++) { //overdraw factor