[escher] create class expression view

Change-Id: I16ddd22318ad120d736ad7f10bb2800a13c2b005

escher/src/expression_view.cpp

@@ -0,0 +1,37 @@
+#include <escher/expression_view.h>
+
+ExpressionView::ExpressionView() :
+  m_expressionLayout(nullptr),
+  m_textColor(KDColorBlack),
+  m_backgroundColor(KDColorWhite)
+{
+}
+
+void ExpressionView::setExpression(ExpressionLayout * expressionLayout) {
+  m_expressionLayout = expressionLayout;
+}
+
+void ExpressionView::setBackgroundColor(KDColor backgroundColor) {
+  m_backgroundColor = backgroundColor;
+}
+
+void ExpressionView::setTextColor(KDColor textColor) {
+  m_textColor = textColor;
+}
+
+KDSize ExpressionView::minimalSizeForOptimalDisplay() {
+  if (m_expressionLayout ==  nullptr) {
+    return KDSizeZero;
+  }
+  return m_expressionLayout->size();
+}
+
+void ExpressionView::drawRect(KDContext * ctx, KDRect rect) const {
+  ctx->fillRect(rect, m_backgroundColor);
+  if (m_expressionLayout != nullptr) {
+    //Position the origin of expression
+    KDSize expressionSize = m_expressionLayout->size();
+    KDPoint origin(0, 0.5f*(m_frame.height() - expressionSize.height()));
+    m_expressionLayout->draw(ctx, origin, m_textColor, m_backgroundColor);
+  }
+}