Kinda closer to correct error phasing for adjacent parallel lines

Author: jamwaffles

debug-tools/examples/thick-line-mul-256.rs

@@ -191,6 +191,8 @@ fn thickline(
         },
     );
 
+    let mut parallel_error = 2 * parallel_delta.minor + parallel_delta.major;
+
     while thickness_accumulator.pow(2) <= thickness_threshold {
         let p = Point::new(
             if seed_is_y_major {
@@ -248,6 +250,7 @@ fn thickline(
 
             if prev.x != p.x {
                 mul_point += parallel_step_full.major;
+                parallel_error += 2 * parallel_delta.minor;
             }
 
             parallel_line_2(
@@ -258,6 +261,7 @@ fn thickline(
                 Rgb888::CSS_AQUAMARINE,
                 display,
                 true,
+                parallel_error,
             )?;
 
             thickness_accumulator += 2 * thickness_dy;
@@ -277,7 +281,7 @@ fn thickline(
         thickness_accumulator += 2 * thickness_dx;
         seed_point += seed_step.major * 2;
         mul_point += parallel_step_full.minor * -1 * 2;
-
+        // parallel_error += 2 * parallel_delta.minor;
         prev = p;
     }
 
@@ -441,6 +445,7 @@ fn parallel_line_2(
     c: Rgb888,
     display: &mut impl DrawTarget<Color = Rgb888, Error = std::convert::Infallible>,
     extra: bool,
+    initial_error: i32,
 ) -> Result<(), std::convert::Infallible> {
     let mut point = start;
 
@@ -453,7 +458,8 @@ fn parallel_line_2(
     let e_major = 2 * dy;
     let length = dx;
     // Setting this to zero causes the first segment before the minor step to be too long
-    let mut error = 2 * dy - dx;
+    // let mut error = 2 * dy - dx;
+    let mut error = initial_error;
 
     for _i in 0..length {
         let p = Point::new(