Add some widget layout and ability event handling.

src/ui_elements/widgets/VerticalSpacer.cpp

@@ -0,0 +1,52 @@
+#include "VerticalSpacer.h"
+
+#include <algorithm>
+#include <numeric>
+
+VerticalSpacer::VerticalSpacer()
+    : Widget(),
+      mScales()
+{
+
+}
+
+std::unique_ptr<VerticalSpacer> VerticalSpacer::Create()
+{
+    return std::make_unique<VerticalSpacer>();
+}
+
+void VerticalSpacer::AddWidget(WidgetUPtr widget)
+{
+    AddWidgetWithScale(std::move(widget), 1.0);
+}
+
+void VerticalSpacer::AddWidgetWithScale(WidgetUPtr widget, double scale)
+{
+    Widget::AddWidget(std::move(widget));
+    mScales.push_back(scale);
+}
+
+void VerticalSpacer::AddChildLayers(const PaintEvent* event)
+{
+    mLayers.clear();
+    double scaleSum  = std::accumulate(mScales.begin(), mScales.end(), 0.0);
+    double offset = 0;
+    unsigned delta = mWidth / mChildren.size();
+    for(std::size_t idx=0; idx<mChildren.size(); idx++)
+    {
+        auto& child = mChildren[idx];
+        double scale = mScales[idx];
+        double delta = mWidth * (scale/scaleSum);
+        child->SetSize(delta, mHeight);
+        child->SetLocation(DiscretePoint(mLocation.GetX() + offset, mLocation.GetY()));
+        child->OnPaintEvent(event);
+        auto layers = child->GetLayers();
+        mLayers.insert(mLayers.end(), layers.begin(), layers.end());
+        offset += delta;
+    }
+}
+
+void VerticalSpacer::OnPaintEvent(const PaintEvent* event)
+{
+    AddChildLayers(event);
+}