SDLPP: add option to specify render object alignment

sdlpp/sdlpp_linerenderer.cpp

@@ -97,10 +97,6 @@ void LineRenderer::updateSizeAndPosition() {
                             collisionWidth(), collisionHeight(), getId() );
     }
 }
-void LineRenderer::centerX() {
-    centerx = true;
-    updateSizeAndPosition();
-}
 std::shared_ptr< RenderObject > LineRenderer::copySelf() {
     auto ret = std::make_shared< LineRenderer >( *this );
     copyTo( ret );
@@ -120,26 +116,8 @@ LineRenderer::getDoubleRect() const {
 }
 
 void LineRenderer::updateXY() {
-    if ( !centerx ) {
-        current = original;
-        return;
-    }
-    auto width = renderer->getWidth();
-    auto height = renderer->getHeight();
-    double x1_, x2_, y1_, y2_;
-    if ( width > height ) {
-        auto multiplier =
-            static_cast< double >( width ) / static_cast< double >( height );
-        x1_ = original.getStart().getX() +
-              static_cast< double >( multiplier - 1 ) / 2;
-        x2_ = original.getEnd().getX() +
-              static_cast< double >( multiplier - 1 ) / 2;
-    } else {
-        x1_ = original.getStart().getX();
-        x2_ = original.getEnd().getX();
-    }
-    y1_ = original.getStart().getY();
-    y2_ = original.getEnd().getY();
-    current = { { x1_, y1_ }, { x2_, y2_ } };
+    auto additions = computeAlignmentAdditions();
+    current = { original.getStart() + additions,
+                original.getEnd() + additions };
 }
 } // namespace SDLPP