canvas::BoxLayout: set stretch factor by item.

simgear/canvas/layout/BoxLayout.cxx

@@ -152,6 +152,24 @@ namespace canvas
     invalidate();
   }
 
+  //----------------------------------------------------------------------------
+  bool BoxLayout::setStretchFactor(const LayoutItemRef& item, int stretch)
+  {
+    for( LayoutItems::iterator it = _layout_items.begin();
+                               it != _layout_items.end();
+                             ++it )
+    {
+      if( item == it->layout_item )
+      {
+        it->stretch = std::max(0, stretch);
+        invalidate();
+        return true;
+      }
+    }
+
+    return false;
+  }
+
   //----------------------------------------------------------------------------
   int BoxLayout::stretch(size_t index) const
   {

simgear/canvas/layout/BoxLayout.hxx

@@ -66,6 +66,14 @@ namespace canvas
        */
       void setStretch(size_t index, int stretch);
 
+      /**
+       * Set the stretch factor of the given @a item to @a stretch, if it exists
+       * in this layout.
+       *
+       * @return true, if the @a item was found in the layout
+       */
+      bool setStretchFactor(const LayoutItemRef& item, int stretch);
+
       /**
        * Get the stretch factor of the item at position @a index
        */

simgear/canvas/layout/canvas_layout_test.cxx

@@ -216,6 +216,15 @@ BOOST_AUTO_TEST_CASE( horizontal_layout )
 
     BOOST_CHECK_EQUAL(w1->geometry(), SGRecti(0,   0, 125, 32));
     BOOST_CHECK_EQUAL(w2->geometry(), SGRecti(130, 0, 126, 32));
+
+    BOOST_REQUIRE( hbox.setStretchFactor(w1, 2) );
+    BOOST_REQUIRE( hbox.setStretchFactor(w2, 3) );
+    BOOST_CHECK_EQUAL(hbox.stretch(0), 2);
+    BOOST_CHECK_EQUAL(hbox.stretch(1), 3);
+
+    hbox.removeItem(w1);
+
+    BOOST_CHECK( !hbox.setStretchFactor(w1, 0) );
   }
 }