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;
+        uint8_t tabstop = iterator.piece_table->tabstop;
-        column -= column % 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();

src/gui/Window.cc

@@ -133,6 +133,7 @@ bool Window::create(std::shared_ptr<Buffer> buffer)
     m_buffer = buffer;
     m_cursor = m_buffer->piece_table->add_cursor();
     m_start_piece = m_buffer->piece_table->start_piece->next;
+    m_cursor_row = 0;
 
     resize();
 
@@ -232,15 +233,45 @@ void Window::handle_key(uint32_t scancode, uint32_t mod)
     case SDL_SCANCODE_ESCAPE:
         m_exit_requested = true;
         break;
+    case SDL_SCANCODE_H:
+        cursor_left();
+        break;
     case SDL_SCANCODE_J:
-        scroll_down();
+        cursor_down();
         break;
     case SDL_SCANCODE_K:
-        scroll_up();
+        cursor_up();
+        break;
+    case SDL_SCANCODE_L:
+        cursor_right();
         break;
     }
 }
 
+void Window::cursor_left()
+{
+    m_cursor->go_left(1);
+    redraw();
+}
+
+void Window::cursor_right()
+{
+    m_cursor->go_right(1);
+    redraw();
+}
+
+void Window::cursor_up()
+{
+    m_cursor->go_up(1, m_cursor->column);
+    redraw();
+}
+
+void Window::cursor_down()
+{
+    m_cursor->go_down(1, m_cursor->column);
+    redraw();
+}
+
 void Window::scroll_down()
 {
     if ((m_start_piece != m_buffer->piece_table->end_piece) &&
@@ -261,6 +292,71 @@ void Window::scroll_up()
     }
 }
 
+std::pair<int, PieceTable::Cursor> Window::calculate_start_position()
+{
+    m_cursor_row = std::min(m_cursor_row, m_rows - 1);
+    int row = m_cursor_row - m_cursor->column / m_columns;
+    PieceTable::Cursor cursor = *m_cursor;
+    cursor.go_start_of_line();
+    while (row > 0)
+    {
+        if (cursor.go_up(1, 0u))
+        {
+            PieceTable::Cursor c = cursor;
+            c.go_end_of_line();
+            row -= c.column / m_columns + 1;
+        }
+        else
+        {
+            m_cursor_row -= row;
+            row = 0;
+        }
+    }
+    return std::pair<int, PieceTable::Cursor>(row, cursor);
+}
+
+void Window::draw_text()
+{
+    auto start_position = calculate_start_position();
+    int row = start_position.first;
+    PieceTable::Cursor cursor = start_position.second;
+
+    for (;;)
+    {
+        int row_offset = cursor.column / m_columns;
+        int screen_row = row + row_offset;
+        if (screen_row >= m_rows)
+            break;
+        int screen_column = cursor.column % m_columns;
+        if (cursor == *m_cursor)
+            draw_cursor(screen_column, screen_row);
+        if (screen_row >= 0)
+        {
+            uint32_t character = *cursor;
+            if (character != 0xFFFFFFFFu)
+                draw_character(screen_column, screen_row, character);
+        }
+        if (!cursor.go_right(1))
+        {
+            if (!cursor.go_down(1, 0))
+                break;
+            row = screen_row + 1;
+        }
+    }
+}
+
+void Window::draw_character(int screen_column, int screen_row, uint32_t character)
+{
+    m_shaders.text->use();
+    int advance = m_font.get_advance();
+    int line_height = m_font.get_line_height();
+    int x = screen_column * advance;
+    int y = m_height - (screen_row + 1) * line_height;
+    auto g = m_font.get_glyph(character);
+    m_shaders.text->set_position(x, y + m_font.get_baseline_offset());
+    g->render();
+}
+
 void Window::resize()
 {
     SDL_GetWindowSize(m_window, &m_width, &m_height);
@@ -280,52 +376,20 @@ void Window::redraw()
     glClearColor (0.0, 0.0, 0.0, 0.0);
     glClear(GL_COLOR_BUFFER_BIT);
 
-    draw_cursor();
+    draw_text();
-    m_shaders.text->use();
-
-    int advance = m_font.get_advance();
-    int line_height = m_font.get_line_height();
-    int x = 0;
-    int y = m_height - line_height;
-    for (PieceTable::Piece * piece = m_start_piece;
-         piece != m_buffer->piece_table->end_piece;
-         piece = piece->next)
-    {
-        for (int i = 0, len = piece->length; i < len; i++)
-        {
-            uint8_t c = piece->start[i];
-            auto g = m_font.get_glyph(c);
-            m_shaders.text->set_position(x, y + m_font.get_baseline_offset());
-            g->render();
-            if ((i + 1) % m_columns == 0)
-            {
-                y -= line_height;
-                x = 0;
-            }
-            else
-            {
-                x += advance;
-            }
-        }
-        if (piece->eol())
-        {
-            y -= line_height;
-            x = 0;
-        }
-        if (y + line_height < 0)
-        {
-            break;
-        }
-    }
 
     SDL_GL_SwapWindow(m_window);
 }
 
-void Window::draw_cursor()
+void Window::draw_cursor(int screen_column, int screen_row)
 {
+    int advance = m_font.get_advance();
+    int line_height = m_font.get_line_height();
+    int x = screen_column * advance;
+    int y = m_height - (screen_row + 1) * line_height;
     m_cursor_array->bind();
     m_shaders.flat->use();
     m_shaders.flat->set_color(1.0, 0.2, 1.0, 1.0);
-    m_shaders.flat->set_position(0, m_height - m_font.get_line_height());
+    m_shaders.flat->set_position(x, y);
     glDrawArrays(GL_TRIANGLE_FAN, 0, 4);
 }

src/gui/Window.h

@@ -1,6 +1,7 @@
 #ifndef WINDOW_H
 #define WINDOW_H
 
+#include <utility>
 #include <SDL.h>
 #include "TextShader.h"
 #include "FlatShader.h"
@@ -17,11 +18,18 @@ public:
 protected:
     void resize();
     void redraw();
-    void draw_cursor();
+    void draw_cursor(int screen_column, int screen_row);
     void handle_event(SDL_Event & event);
     void handle_key(uint32_t scancode, uint32_t mod);
+    void cursor_left();
+    void cursor_right();
+    void cursor_up();
+    void cursor_down();
     void scroll_down();
     void scroll_up();
+    std::pair<int, PieceTable::Cursor> calculate_start_position();
+    void draw_text();
+    void draw_character(int screen_column, int screen_row, uint32_t character);
 
     SDL_Window * m_window;
     bool m_exit_requested;
@@ -36,6 +44,7 @@ protected:
     Font m_font;
     int m_columns;
     int m_rows;
+    int m_cursor_row;
 
     std::shared_ptr<Buffer> m_buffer;