[poincare] Delete for FractionLayout.

Change-Id: Ifbbe5c434d278e8223ada3d368c1e948712567d2

poincare/src/layout/fraction_layout.cpp

@@ -1,4 +1,6 @@
 #include "fraction_layout.h"
+#include "empty_visible_layout.h"
+#include "horizontal_layout.h"
 #include <escher/metric.h>
 #include <poincare/expression_layout_cursor.h>
 #include <string.h>
@@ -11,6 +13,76 @@ ExpressionLayout * FractionLayout::clone() const {
   return layout;
 }
 
+void FractionLayout::backspaceAtCursor(ExpressionLayoutCursor * cursor) {
+  // If the cursor is on the left of the denominator, replace the fraction with
+  // a horizontal juxtaposition of the numerator and the denominator.
+  if (cursor->pointedExpressionLayout() == denominatorLayout()) {
+    assert(cursor->position() == ExpressionLayoutCursor::Position::Left);
+    if (numeratorLayout()->isEmpty()) {
+      if (denominatorLayout()->isEmpty()) {
+        // If the numerator and the denominator are empty, replace the fraction
+        // with an empty layout.
+        ExpressionLayout * previousParent = m_parent;
+        int indexInParent = previousParent->indexOfChild(this);
+        replaceWith(new EmptyVisibleLayout(), true);
+        // Place the cursor on the right of the left brother ofthe fraction if
+        // there is one.
+        if (indexInParent > 0) {
+          cursor->setPointedExpressionLayout(previousParent->editableChild(indexInParent - 1));
+          cursor->setPosition(ExpressionLayoutCursor::Position::Right);
+          return;
+        }
+        // Else place the cursor on the Left of the parent.
+        cursor->setPointedExpressionLayout(previousParent);
+        return;
+      }
+      // If the numerator is empty but not the denominator, replace the fraction
+      // with its denominator. Place the cursor on the left of the denominator.
+      ExpressionLayout * nextPointedLayout = denominatorLayout();
+      if (denominatorLayout()->isHorizontal()) {
+        nextPointedLayout = denominatorLayout()->editableChild(0);
+      }
+      replaceWith(denominatorLayout(), true);
+      cursor->setPointedExpressionLayout(nextPointedLayout);
+      cursor->setPosition(ExpressionLayoutCursor::Position::Left);
+      return;
+    }
+    // If the denominator is empty but not the numerator, replace the fraction
+    // with the numerator and place the cursor on its right.
+    if (denominatorLayout()->isEmpty()) {
+      ExpressionLayout * nextPointedLayout = numeratorLayout();
+      if (numeratorLayout()->isHorizontal()) {
+        nextPointedLayout = numeratorLayout()->editableChild(numeratorLayout()->numberOfChildren() - 1);
+      }
+      replaceWith(numeratorLayout(), true);
+      cursor->setPointedExpressionLayout(nextPointedLayout);
+      cursor->setPosition(ExpressionLayoutCursor::Position::Right);
+      return;
+    }
+    // If neither the numerator nor the denominator are empty, replace the
+    // fraction with a juxtaposition of the numerator and denominator. Place the
+    // cursor in the middle of the juxtaposition, which is right of the
+    // numerator.
+    ExpressionLayout * nextPointedLayout = numeratorLayout();
+    if (numeratorLayout()->isHorizontal()) {
+      nextPointedLayout = numeratorLayout()->editableChild(numeratorLayout()->numberOfChildren() - 1);
+    }
+    ExpressionLayout * numerator = numeratorLayout();
+    ExpressionLayout * denominator = denominatorLayout();
+    detachChild(numerator);
+    detachChild(denominator);
+    HorizontalLayout * newLayout = new HorizontalLayout();
+    newLayout->addOrMergeChildAtIndex(denominator, 0);
+    newLayout->addOrMergeChildAtIndex(numerator, 0);
+    // Add the denominator before the numerator to have the right order.
+    replaceWith(newLayout, true);
+    cursor->setPointedExpressionLayout(nextPointedLayout);
+    cursor->setPosition(ExpressionLayoutCursor::Position::Right);
+    return;
+  }
+  ExpressionLayout::backspaceAtCursor(cursor);
+}
+
 bool FractionLayout::moveLeft(ExpressionLayoutCursor * cursor) {
   // Case: Left of the numerator or the denominator.
   // Go Left of the fraction.

poincare/src/layout/fraction_layout.h

@@ -9,6 +9,7 @@ class FractionLayout : public StaticLayoutHierarchy<2> {
 public:
   using StaticLayoutHierarchy::StaticLayoutHierarchy;
   ExpressionLayout * clone() const override;
+  void backspaceAtCursor(ExpressionLayoutCursor * cursor) override;
   bool moveLeft(ExpressionLayoutCursor * cursor) override;
   bool moveRight(ExpressionLayoutCursor * cursor) override;
   bool moveUp(ExpressionLayoutCursor * cursor, ExpressionLayout * previousLayout, ExpressionLayout * previousPreviousLayout) override;

poincare/src/layout/horizontal_layout.cpp

@@ -39,6 +39,14 @@ void HorizontalLayout::replaceChild(const ExpressionLayout * oldChild, Expressio
   ExpressionLayout::replaceChild(oldChild, newChild, deleteOldChild);
 }
 
+void HorizontalLayout::addOrMergeChildAtIndex(ExpressionLayout * eL, int index) {
+  if (eL->isHorizontal()) {
+    mergeChildrenAtIndex(eL, index);
+    return;
+  }
+  addChildAtIndex(eL, index);
+}
+
 bool HorizontalLayout::moveLeft(ExpressionLayoutCursor * cursor) {
   // Case: Left.
   // Ask the parent.

poincare/src/layout/horizontal_layout.h

@@ -12,6 +12,7 @@ public:
 
   /* Hierarchy */
   void replaceChild(const ExpressionLayout * oldChild, ExpressionLayout * newChild, bool deleteOldChild = true) override;
+  void addOrMergeChildAtIndex(ExpressionLayout * eL, int index);
 
   /* Navigation */
   bool moveLeft(ExpressionLayoutCursor * cursor) override;