It's working way better now, with correct internal dimensions, but I'm drawing the wrong nodes, need to go depth first.

map.cpp

@@ -93,8 +93,8 @@ void Map::make_room(size_t origin_x, size_t origin_y, size_t w, size_t h) {
   println("MAKE ROOM x={}, y={}, w={}, h={}", origin_x, origin_y, w, h);
   dbc::pre("x out of bounds", origin_x < width());
   dbc::pre("y out of bounds", origin_y < height());
-  dbc::pre("w out of bounds", w < width());
-  dbc::pre("h out of bounds", h < height());
+  dbc::pre("w out of bounds", w <= width());
+  dbc::pre("h out of bounds", h <= height());
 
   for(size_t y = origin_y; y < origin_y + h; ++y) {
     dbc::check(y < m_walls.size(), "y is out of bounds");
@@ -117,28 +117,18 @@ struct Partition {
 };
 
 inline int make_split(std::mt19937 &gen, Partition &cur, bool horiz) {
-  if(horiz) {
-    println("MAKE SPLIT HORIZ, y={}, y+h={}, h={}",
-        cur.y, cur.y + cur.height, cur.height);
-
-    size_t quarter = cur.height / 4;
-    // vertical split, pick a random horizontal location
-    std::uniform_int_distribution<int> rhoriz(cur.y + quarter, cur.y + cur.height - quarter);
-
-    return rhoriz(gen);
-  } else {
-    // horizontal split, pick a random vertical location
-    println("MAKE SPLIT VERT, x={}, x+w={}, w={}",
-        cur.x, cur.x + cur.width, cur.width);
-
-    size_t quarter = cur.width / 4;
-    std::uniform_int_distribution<int> rvert(cur.x + quarter, cur.x + cur.width - quarter);
-    return rvert(gen);
-  }
+  println("MAKE SPLIT horiz={}, y={}, w={}, h={}", horiz,
+        cur.y, cur.width, cur.height);
+  size_t dimension = horiz ? cur.height : cur.width;
+  int min = dimension / 4; // 25% of the dimension
+  int max = dimension - min; // 25% off the other side
+  println("dimension={}, min={}, max={}", dimension, min, max);
+  std::uniform_int_distribution<int> rand_dim(min, max);
+  return rand_dim(gen);
 }
 
 void partition_map(std::mt19937 &gen, Partition &cur, int depth) {
-
+  println(">>>> DEPTH: {}", depth);
   std::uniform_int_distribution<int> rsplit(0, 1);
   bool horiz = rsplit(gen);
   int split = make_split(gen, cur, horiz);
@@ -150,7 +140,7 @@ void partition_map(std::mt19937 &gen, Partition &cur, int depth) {
         split, cur.x, cur.y, cur.width, cur.height);
 
     dbc::check(split > 0, "split is not > 0");
-    dbc::check(split < int(cur.y + cur.height), "split is too big!");
+    dbc::check(split < int(cur.height), "split is too big!");
 
     left = {
       .x = cur.x,
@@ -163,13 +153,13 @@ void partition_map(std::mt19937 &gen, Partition &cur, int depth) {
       .x = cur.x,
       .y = cur.y + split,
       .width = cur.width,
-      .height = size_t(cur.y + cur.height - split)
+      .height = size_t(cur.height - split)
     };
   } else {
     println("VERT split={}, x={}, y={}, w={}, h={}", split, cur.x, cur.y, cur.width, cur.height);
 
     dbc::check(split > 0, "split is not > 0");
-    dbc::check(split < int(cur.x + cur.width), "split is too big!");
+    dbc::check(split < int(cur.width), "split is too big!");
 
     left = {
       .x = cur.x,
@@ -186,31 +176,28 @@ void partition_map(std::mt19937 &gen, Partition &cur, int depth) {
     };
   }
 
-  println("CUR NEXT SIZE={}", cur.next.size());
-
-  if(depth > 0  && left.width > 10 && left.height > 10) {
+  if(depth > 0  && left.width > 5 && left.height > 5) {
+    println("### LEFT h={}, w={}", left.width, left.height);
     partition_map(gen, left, depth-1);
+    cur.next.push_back(left);
   }
 
-  if(depth > 0 && right.width > 10 && right.height > 10) {
+  if(depth > 0 && right.width > 5 && right.height > 5) {
+    println("### RIGHT h={}, w={}", right.width, right.height);
     partition_map(gen, right, depth-1);
+    cur.next.push_back(right);
   }
-
-  println("PUSH CHILD!");
-  cur.next.push_back(left);
-  println("PUSH CHILD!");
-  cur.next.push_back(right);
 }
 
-void draw_map(Map *map, Partition &root, Partition &cur) {
+void draw_map(Map *map, Partition &cur) {
   if(cur.x + cur.width <= map->width()
       && cur.y + cur.height <= map->height())
   {
     map->make_room(cur.x, cur.y, cur.width, cur.height);
 
     if(cur.next.size() == 2) {
-      draw_map(map, root, cur.next[0]); // left
-      draw_map(map, root, cur.next[1]); // right
+      draw_map(map, cur.next[0]); // left
+      draw_map(map, cur.next[1]); // right
     } else {
       println("LEAF NODE NO CHILDREN");
     }
@@ -225,15 +212,12 @@ void Map::generate() {
   std::mt19937 gen(rd());
 
   Partition root{
-    .x = 1,
-    .y = 1,
-    .width = width() - 2,
-    .height = height() - 2
+    .x = 0,
+    .y = 0,
+    .width = width(),
+    .height = height()
   };
 
-  partition_map(gen, root, 3);
-  println("ROOT LEFT HAS {} CHILD", root.next[0].next.size());
-  draw_map(this, root, root.next[0]); // left
-  println("ROOT RIGHT HAS {} CHILD", root.next[1].next.size());
-  draw_map(this, root, root.next[1]); // right
+  partition_map(gen, root, 5);
+  draw_map(this, root); // left
 }