give a recipe line its own row for its identity

src/ui/RecipeLineRow.h

@@ -13,9 +13,10 @@ class BuildingIconCache;
 class ItemIconCache;
 class QHBoxLayout;
 
-// One recipe drawn on a line: what it consumes, an arrow, what it produces, and how
-// long a cycle takes (REQ-UI-RECIPE-SUMMARY). Every place the UI states what something
-// makes draws this same line, so a recipe reads alike wherever it is shown:
+// One recipe drawn: what it consumes, an arrow, what it produces, and how long a cycle
+// takes (REQ-UI-RECIPE-SUMMARY), under a header naming the building that runs it and the
+// recipe itself where the recipe has to identify itself. Every place the UI states what
+// something makes draws this same line, so a recipe reads alike wherever it is shown:
 //
 //  * beneath the selection button, for the recipe a building is running
 //    (REQ-UI-RECIPE-SUMMARY);
@@ -48,12 +49,13 @@ public:
     // lines.
     struct Spec
     {
-        // Drawn as a leading chip when the line has to say which building runs the
-        // recipe -- an item may have several producers (REQ-UI-ITEM-TOOLTIP). Unset
-        // wherever the surrounding widget already establishes the building.
+        // The chip of the building running the recipe, on the header line, where the
+        // recipe has to say which building that is -- an item may have several producers
+        // (REQ-UI-ITEM-TOOLTIP). Unset wherever the surrounding widget already
+        // establishes the building, and the header line is then left out entirely.
         std::optional<BuildingType> building;
-        // Leading recipe name, for the same reason. Empty where the name is the
-        // caption above the line instead.
+        // The recipe's name, beside the building chip on the header line. Empty where the
+        // name is the caption of the widget around this one instead.
         QString                     name;
         std::vector<Amount>         inputs;
         // Empty for a line that produces no item of its own: a ship schematic, or a
@@ -91,7 +93,13 @@ private:
 
     ItemIconCache*     m_itemIcons;
     BuildingIconCache* m_buildingIcons;
-    QHBoxLayout*       m_layout;
+    // The two lines, each a row widget of its own so a rebuild only has to empty their
+    // layouts -- no nested layout to take apart. The header is hidden where the spec
+    // names neither a building nor a recipe.
+    QWidget*           m_headerRow;
+    QHBoxLayout*       m_headerLayout;
+    QWidget*           m_amountsRow;
+    QHBoxLayout*       m_amountsLayout;
     // What the row currently shows, so a refresh at tick rate rebuilds it only when the
     // recipe actually changed.
     Spec               m_spec;