give core better padding

bench/core_widget.cpp

@@ -119,9 +119,27 @@ void core_widget::draw(int width, int height) {
       }
     }
 
-    cpr = width / scale;
+    cpr = width / scale + 1;
-    xpad = (width % scale) / 2;
+    xpad = INT_MAX;
-    ypad = (height % scale) / 2;
+    ypad = 0;
+
+    while (cpr >= 1) {
+      --cpr;
+
+      int rows = (LIB94_CORE_SIZE - 1) / cpr + 1;
+      int new_xpad = (width - cpr * scale) / 2;
+      int new_ypad = (height - rows * scale) / 2;
+
+      if (abs(new_xpad - new_ypad) < abs(xpad - ypad)) {
+        xpad = new_xpad;
+        ypad = new_ypad;
+      }
+
+      else {
+        ++cpr;
+        break;
+      }
+    }
 
     uint8_t *buffer = (uint8_t *)pixbuf->property_pixels().get_value();