Draw text based on new cursor movement system

The cursor row still locked to the first row for now

src/core/PieceTable.cc

@@ -118,22 +118,27 @@ void PieceTable::Iterator::go_prev_piece()
 
 PieceTable::Cursor::Cursor(PieceTable * pt) : iterator(pt)
 {
-    line = iterator.valid() ? 1u : 0u;
+    line = 0u;
     init_column();
 }
 
 void PieceTable::Cursor::go_start_of_line()
 {
-    while (iterator.valid() && (!iterator.piece->prev->eol()))
+    while (iterator.valid() &&
+            (!iterator.piece->prev->eol()) &&
+            (iterator.piece->prev != iterator.piece_table->start_piece))
     {
         iterator.go_prev_piece();
     }
+    iterator.offset = 0u;
     init_column();
 }
 
 void PieceTable::Cursor::go_end_of_line()
 {
-    while (iterator.valid() && (!iterator.piece->eol()))
+    while (iterator.valid() &&
+            (!iterator.piece->eol()) &&
+            (iterator.piece->next != iterator.piece_table->end_piece))
     {
         iterator.go_next_piece();
     }
@@ -201,8 +206,8 @@ bool PieceTable::Cursor::go_right(int n)
     uint32_t chr = *iterator;
     if (chr == '\t')
     {
-        column += iterator.piece_table->tabstop;
-        column -= column % iterator.piece_table->tabstop;
+        uint8_t tabstop = iterator.piece_table->tabstop;
+        column += tabstop - (column + 1u) % tabstop;
     }
     else
     {
@@ -216,14 +221,15 @@ bool PieceTable::Cursor::is_start_of_line()
 {
     return iterator.valid() &&
         (iterator.offset == 0u) &&
-        (iterator.piece->prev->eol());
+        ((iterator.piece->prev == iterator.piece_table->start_piece) ||
+         iterator.piece->prev->eol());
 }
 
 bool PieceTable::Cursor::is_end_of_line()
 {
     return iterator.valid() &&
          ((iterator.offset + iterator.num_bytes_in_code_point()) >= iterator.piece->length) &&
-         iterator.piece->eol();
+         (iterator.piece->eol() || (iterator.piece->next == iterator.piece_table->end_piece));
 }
 
 PieceTable::Piece * PieceTable::Cursor::prev_line() const
@@ -268,7 +274,7 @@ void PieceTable::Cursor::init_column()
 {
     uint32_t chr = *iterator;
     /* TODO: handle multi-column characters */
-    column = (chr == 0xFFFFFFFFu) ? 0u : (chr == '\t') ? iterator.piece_table->tabstop : 1u;
+    column = (chr == '\t') ? iterator.piece_table->tabstop - 1u : 0u;
 }
 
 void PieceTable::Cursor::calculate_column()
@@ -286,6 +292,8 @@ void PieceTable::Cursor::calculate_column()
 void PieceTable::Cursor::forward_to_column(uint32_t c)
 {
     int32_t diff = abs((int32_t)(c - column));
+    if (diff == 0)
+        return;
     while (go_right(1))
     {
         int32_t new_diff = abs((int32_t)(c - column));

src/core/PieceTable.h

@@ -116,6 +116,10 @@ public:
         bool go_down(int n, uint32_t desired_column);
         bool go_left(int n);
         bool go_right(int n);
+        bool operator==(const Cursor & c)
+        {
+            return (c.line == line) && (c.column == column);
+        }
 
     protected:
         bool is_start_of_line();