First cut at a replica of the python raycaster. Left side almost works the same but have to sort out math differences.

matrix.cpp

@@ -0,0 +1,94 @@
+#include "matrix.hpp"
+#include "dbc.hpp"
+#include <fmt/core.h>
+#include <cmath>
+#include <cstdlib>
+
+using namespace fmt;
+using std::min, std::max;
+
+namespace matrix {
+
+  flood::flood(Matrix &mat, Point start, int old_val, int new_val) :
+    mat(mat), start(start), old_val(old_val), new_val(new_val),
+     x(start.x), y(start.y), dirs{mat, start.x, start.y}
+  {
+    dbc::check(old_val != new_val, "what you doing?");
+    current_loc = start;
+    q.push(start);
+  }
+
+  bool flood::next() {
+    if(!q.empty()) {
+      if(!dirs.next()) {
+        // box is done reset it
+        auto current_loc = q.front();
+        q.pop();
+
+        dirs = matrix::compass{mat, current_loc.x, current_loc.y};
+        dirs.next();
+      }
+
+      // get the next thing
+      if(mat[dirs.y][dirs.x] <= old_val) {
+        mat[dirs.y][dirs.x] = new_val;
+        x = dirs.x;
+        y = dirs.y;
+
+        q.push({.x=dirs.x, .y=dirs.y});
+      }
+
+      return true;
+    } else {
+      return false;
+    }
+  }
+
+  line::line(Point start, Point end) :
+      x(start.x), y(start.y),
+      x1(end.x), y1(end.y)
+  {
+    dx = std::abs(x1 - x);
+    sx = x < x1 ? 1 : -1;
+    dy = std::abs(y1 - y) * -1;
+    sy = y < y1 ? 1 : -1;
+    error = dx + dy;
+  }
+
+  bool line::next() {
+    if(x != x1 || y != y1) {
+      int e2 = 2 * error;
+
+      if(e2 >= dy) {
+        error = error + dy;
+        x = x + sx;
+      }
+
+      if(e2 <= dx) {
+        error = error + dx;
+        y = y + sy;
+      }
+      return true;
+    } else {
+      return false;
+    }
+  }
+
+  void dump(const std::string &msg, Matrix &map, int show_x, int show_y) {
+    println("----------------- {}", msg);
+
+    for(each_row it{map}; it.next();) {
+      int cell = map[it.y][it.x];
+
+      if(int(it.x) == show_x && int(it.y) == show_y) {
+        print("{:x}<", cell);
+      } else if(cell > 15) {
+        print("* ");
+      } else {
+        print("{:x} ", cell);
+      }
+
+      if(it.row) print("\n");
+    }
+  }
+}