Declare parallel Bresenham stuff outside loop

Author: jamwaffles

debug-tools/examples/mul-both-axes.rs

@@ -149,14 +149,18 @@ fn thickline(
 
     let dx = seed_delta_majorminor.major.abs();
     let dy = seed_delta_majorminor.minor.abs();
+    let parallel_dx = parallel_delta_majorminor.major.abs();
+    let parallel_dy = parallel_delta_majorminor.minor.abs();
 
     // http://kt8216.unixcab.org/murphy/index.html calls e_minor E_diag, and e_major E_square
     let e_minor = -2 * dx;
     let e_major = 2 * dy;
+    let parallel_e_minor = -2 * parallel_dx;
+    let parallel_e_major = 2 * parallel_dy;
 
     let mut seed_line_error = 2 * dy - dx;
+    let mut parallel_error = 2 * parallel_dy - parallel_dx;
     let mut point = seed_line.start;
-    let mut prev = point;
     let mut parallel_point = line.start;
 
     for i in 0..width {
@@ -190,14 +194,7 @@ fn thickline(
 
         // Draw parallel line
         {
-            let dx = parallel_delta_majorminor.major.abs();
-            let dy = parallel_delta_majorminor.minor.abs();
-
-            // http://kt8216.unixcab.org/murphy/index.html calls e_minor E_diag, and e_major E_square
-            let e_minor = -2 * dx;
-            let e_major = 2 * dy;
-
-            let mut parallel_line_error = 2 * dy - dx;
+            let mut parallel_line_error = parallel_error;
             let mut point = parallel_point;
 
             for i in 0..original_delta_majorminor.major.abs() {
@@ -207,14 +204,17 @@ fn thickline(
 
                 if parallel_line_error > 0 {
                     point += parallel_step_majorminor.minor;
-                    parallel_line_error += e_minor;
+                    parallel_line_error += parallel_e_minor;
                 }
 
                 point += parallel_step_majorminor.major;
-                parallel_line_error += e_major;
+                parallel_line_error += parallel_e_major;
             }
         }
 
+        // In the two blocks below, we could fix phasing here by moving `parallel_point` the right
+        // amount. What is that amount though??
+
         if seed_line_error > 0 {
             point += seed_step_majorminor.minor;
             parallel_point += seed_step_majorminor.minor;
@@ -228,14 +228,7 @@ fn thickline(
 
     // Draw AA line
     {
-        let dx = parallel_delta_majorminor.major.abs();
-        let dy = parallel_delta_majorminor.minor.abs();
-
-        // http://kt8216.unixcab.org/murphy/index.html calls e_minor E_diag, and e_major E_square
-        let e_minor = -2 * dx;
-        let e_major = 2 * dy;
-
-        let mut parallel_line_error = 2 * dy - dx;
+        let mut parallel_line_error = parallel_error;
         let mut point = parallel_point;
 
         for i in 0..original_delta_majorminor.major.abs() {
@@ -265,11 +258,11 @@ fn thickline(
 
             if parallel_line_error > 0 {
                 point += parallel_step_majorminor.minor;
-                parallel_line_error += e_minor;
+                parallel_line_error += parallel_e_minor;
             }
 
             point += parallel_step_majorminor.major;
-            parallel_line_error += e_major;
+            parallel_line_error += parallel_e_major;
         }
     }