[poincare] Create a class subscript layout

Change-Id: I3496f1942ed661f751612472f72e1d11fffa1ccc

poincare/Makefile

@@ -46,6 +46,7 @@ objs += $(addprefix poincare/src/layout/,\
   nth_root_layout.o\
   parenthesis_layout.o\
   string_layout.o\
+  subscript_layout.o\
 )
 
 tests += $(addprefix poincare/test/,\

poincare/src/layout/subscript_layout.cpp

@@ -0,0 +1,49 @@
+#include "subscript_layout.h"
+#include <string.h>
+#include <assert.h>
+
+SubscriptLayout::SubscriptLayout(ExpressionLayout * baseLayout, ExpressionLayout * subscriptLayout) :
+  ExpressionLayout(),
+  m_baseLayout(baseLayout),
+  m_subscriptLayout(subscriptLayout)
+{
+  m_baseLayout->setParent(this);
+  m_subscriptLayout->setParent(this);
+  m_baseline = m_baseLayout->baseline();
+}
+
+SubscriptLayout::~SubscriptLayout() {
+  delete m_baseLayout;
+  delete m_subscriptLayout;
+}
+
+void SubscriptLayout::render(KDContext * ctx, KDPoint p, KDColor expressionColor, KDColor backgroundColor) {
+  // There is nothing to draw for a power, only the position of the children matters
+}
+
+KDSize SubscriptLayout::computeSize() {
+  KDSize baseSize = m_baseLayout->size();
+  KDSize subscriptSize = m_subscriptLayout->size();
+  return KDSize(baseSize.width() + subscriptSize.width(), m_baseLayout->baseline() + subscriptSize.height() - k_subscriptHeight);
+}
+
+ExpressionLayout * SubscriptLayout::child(uint16_t index) {
+  switch (index) {
+    case 0:
+      return m_baseLayout;
+    case 1:
+      return m_subscriptLayout;
+    default:
+      return nullptr;
+  }
+}
+
+KDPoint SubscriptLayout::positionOfChild(ExpressionLayout * child) {
+  KDCoordinate x = 0;
+  KDCoordinate y = 0;
+  if (child == m_subscriptLayout) {
+    x = m_baseLayout->size().width();
+    y = m_baseLayout->baseline() - k_subscriptHeight;
+  }
+  return KDPoint(x,y);
+}

poincare/src/layout/subscript_layout.h

@@ -0,0 +1,22 @@
+#ifndef POINCARE_SUBSCRIPT_LAYOUT_H
+#define POINCARE_SUBSCRIPT_LAYOUT_H
+
+#include <poincare/expression.h>
+#include <poincare/expression_layout.h>
+
+class SubscriptLayout : public ExpressionLayout {
+  public:
+    SubscriptLayout(ExpressionLayout * baseLayout, ExpressionLayout * subscriptLayout);
+    ~SubscriptLayout();
+  protected:
+    void render(KDContext * ctx, KDPoint p, KDColor expressionColor, KDColor backgroundColor) override;
+    KDSize computeSize() override;
+    ExpressionLayout * child(uint16_t index) override;
+    KDPoint positionOfChild(ExpressionLayout * child) override;
+  private:
+    constexpr static KDCoordinate k_subscriptHeight = 5;
+    ExpressionLayout * m_baseLayout;
+    ExpressionLayout * m_subscriptLayout;
+};
+
+#endif