Fix Terminal character position and add word selection (#906)

* Improve horizontal interactive selection
* Using half-character positions to implement selection
  similar to Fl_Input.
* Add word and line selection
* Fix vertical position of text

FL/Fl_Terminal.H

@@ -669,30 +669,34 @@ private:
   // Class to manage mouse selection
   //
   class FL_EXPORT Selection {
+    Fl_Terminal *terminal_;
     int srow_, scol_, erow_, ecol_;     // selection start/end. NOTE: start *might* be > end
     int push_row_, push_col_;           // global row/col for last FL_PUSH
+    bool push_char_right_;
     Fl_Color selectionbgcolor_;
     Fl_Color selectionfgcolor_;
     int state_ ;                        // 0=none, 1=started, 2=extended, 3=done
     bool is_selection_;                 // false: no selection
   public:
-    Selection(void);
+    Selection(Fl_Terminal *terminal);
     int srow(void) const { return srow_; }
     int scol(void) const { return scol_; }
     int erow(void) const { return erow_; }
     int ecol(void) const { return ecol_; }
-    void push_clear() { push_row_ = push_col_ = -1; }
+    void push_clear() { push_row_ = push_col_ = -1; push_char_right_ = false; }
-    void push_rowcol(int row,int col) { push_row_ = row; push_col_ = col; }
+    void push_rowcol(int row,int col,bool char_right) {
-    void start_push() { start(push_row_, push_col_); }
+      push_row_ = row; push_col_ = col; push_char_right_ = char_right; }
-    bool dragged_off(int row,int col) { return (push_row_ != row) || (push_col_ != col); }
+    void start_push() { start(push_row_, push_col_, push_char_right_); }
+    bool dragged_off(int row,int col,bool char_right) {
+      return (push_row_ != row) || (push_col_+push_char_right_ != col+char_right); }
     void selectionfgcolor(Fl_Color val) { selectionfgcolor_ = val; }
     void selectionbgcolor(Fl_Color val) { selectionbgcolor_ = val; }
     Fl_Color selectionfgcolor(void) const { return selectionfgcolor_; }
     Fl_Color selectionbgcolor(void) const { return selectionbgcolor_; }
     bool is_selection(void) const { return is_selection_; }
     bool get_selection(int &srow,int &scol,int &erow,int &ecol) const; // guarantees return (start < end)
-    bool start(int row, int col);
+    bool start(int row, int col, bool char_right);
-    bool extend(int row, int col);
+    bool extend(int row, int col, bool char_right);
     void end(void);
     void select(int srow, int scol, int erow, int ecol);
     bool clear(void);
@@ -882,8 +886,8 @@ protected:
   CharStyle& current_style(void) const;
   void current_style(const CharStyle& sty);
 private:
-  int  x_to_glob_col(int X, int grow, int &gcol) const;
+  int  x_to_glob_col(int X, int grow, int &gcol, bool &gcr) const;
-  int  xy_to_glob_rowcol(int X, int Y, int &grow, int &gcol) const;
+  int  xy_to_glob_rowcol(int X, int Y, int &grow, int &gcol, bool &gcr) const;
 protected:
   int  w_to_col(int W) const;
   int  h_to_row(int H) const;
@@ -906,6 +910,8 @@ protected:
   const char* selection_text(void) const;
   void clear_mouse_selection(void);
   bool selection_extend(int X,int Y);
+  void select_word(int grow, int gcol);
+  void select_line(int grow);
   void scroll(int rows);
   void insert_rows(int count);
   void delete_rows(int count);

src/Fl_Terminal.cxx

@@ -137,7 +137,9 @@ static bool is_frame(Fl_Boxtype b) {
 ///////////////////////////////////////
 
 // Ctor
-Fl_Terminal::Selection::Selection(void) {
+Fl_Terminal::Selection::Selection(Fl_Terminal *terminal) 
+  : terminal_(terminal)
+{
   // These are used to set/get the mouse selection
   srow_ = scol_ = erow_ = ecol_ = 0;
   // FL_PUSH event row/col
@@ -172,7 +174,7 @@ bool Fl_Terminal::Selection::get_selection(int &srow,int &scol,
 // Start new selection at specified row,col
 //    Always returns true.
 //
-bool Fl_Terminal::Selection::start(int row, int col) {
+bool Fl_Terminal::Selection::start(int row, int col, bool char_right) {
   srow_ = erow_ = row;
   scol_ = ecol_ = col;
   state_ = 1;                                      // state: "started selection"
@@ -183,14 +185,42 @@ bool Fl_Terminal::Selection::start(int row, int col) {
 // Extend existing selection to row,col
 //     Returns true if anything changed, false if not.
 //
-bool Fl_Terminal::Selection::extend(int row, int col) {
+bool Fl_Terminal::Selection::extend(int row, int col, bool char_right) {
   // no selection started yet? start and return true
-  if (!is_selection()) return start(row, col);
+  int osrow = srow_, oerow = erow_, oscol = scol_, oecol = ecol_;
+  int oselection = is_selection_;
+  if (state_ == 0) return start(row, col, char_right);
   state_ = 2;                                      // state: "extending selection"
-  if (erow_ == row && ecol_ == col) return false;  // no change
+
+  if ((row==push_row_) && (col+char_right==push_col_+push_char_right_)) {
+    // we are in the box of the original push event
+    srow_ = erow_ = row;
+    scol_ = ecol_ = col;
+    is_selection_ = false;
+  } else if ((row>push_row_) || ((row==push_row_) && (col+char_right>push_col_+push_char_right_))) {
+    // extend to the right and down
+    scol_ = push_col_ + push_char_right_;
+    ecol_ = col - 1 + char_right;
+    is_selection_ = true;
+  } else {
+    // extend to the left and up
+    scol_ = push_col_ - 1 + push_char_right_;
+    ecol_ = col + char_right;
+    is_selection_ = true;
+  }
+
+  if (scol_<0) scol_ = 0;
+  if (ecol_<0) ecol_ = 0;
+  int maxCol = terminal_->ring_cols()-1;
+  if (scol_>maxCol) scol_ = maxCol;
+  if (ecol_>maxCol) ecol_ = maxCol;
+  srow_ = push_row_;
   erow_ = row;
-  ecol_ = col;
+
-  return true;
+  bool changed = (   (osrow != srow_) || (oerow != erow_)
+                  || (oscol != scol_) || (oecol != ecol_)
+                  || (oselection != is_selection_) );
+  return !changed;
 }
 
 // End selection (turn dragging() off)
@@ -1718,13 +1748,16 @@ uchar Fl_Terminal::textattrib() const {
     - 1 if 'gcol' was found
     - 0 if X not within any char in 'grow'
 */
-int Fl_Terminal::x_to_glob_col(int X, int grow, int &gcol) const {
+int Fl_Terminal::x_to_glob_col(int X, int grow, int &gcol, bool &gcr) const {
-  int cx = x() + margin_.left();                    // char x position
+  int cx = scrn_.x();                               // leftmost char x position
   const Utf8Char *u8c = utf8_char_at_glob(grow, 0);
   for (gcol=0; gcol<ring_cols(); gcol++,u8c++) {    // walk the cols looking for X
     u8c->fl_font_set(*current_style_);              // pwidth_int() needs fl_font set
     int cx2 = cx + u8c->pwidth_int();               // char x2 (right edge of char)
-    if (X >= cx && X < cx2) return 1;               // found? return with gcol set
+    if (X >= cx && X < cx2) {
+      gcr = (X > ((cx+cx2)/2));                     // X is in right half of character
+      return 1;                                     // found? return with gcol and gcr set
+    }
     cx += u8c->pwidth_int();                        // move cx to start x of next char
   }
   gcol = ring_cols()-1;                             // don't leave larger than #cols
@@ -1737,7 +1770,7 @@ int Fl_Terminal::x_to_glob_col(int X, int grow, int &gcol) const {
 //              0 -- not found, outside display's character area
 //    -1/-2/-3/-4 -- not found, off top/bot/lt/rt edge respectively
 //
-int Fl_Terminal::xy_to_glob_rowcol(int X, int Y, int &grow, int &gcol) const {
+int Fl_Terminal::xy_to_glob_rowcol(int X, int Y, int &grow, int &gcol, bool &gcr) const {
   // X,Y outside terminal area? early exit
   if (Y<scrn_.y()) return -1;                       // up (off top edge)
   if (Y>scrn_.b()) return -2;                       // dn (off bot edge)
@@ -1747,7 +1780,7 @@ int Fl_Terminal::xy_to_glob_rowcol(int X, int Y, int &grow, int &gcol) const {
   int toprow = disp_srow() - scrollbar->value();
   // Find row the 'Y' value is in
   grow = toprow + ( (Y-scrn_.y()) / current_style_->fontheight());
-  return x_to_glob_col(X, grow, gcol);
+  return x_to_glob_col(X, grow, gcol, gcr);
 }
 
 /**
@@ -2051,9 +2084,10 @@ void Fl_Terminal::clear_mouse_selection(void) {
 */
 bool Fl_Terminal::selection_extend(int X,int Y) {
   if (is_selection()) {                  // selection already?
-    int grow,gcol;
+    int grow, gcol;
-    if (xy_to_glob_rowcol(X, Y, grow, gcol) > 0) {
+    bool gcr;
-      select_.extend(grow, gcol);        // extend it
+    if (xy_to_glob_rowcol(X, Y, grow, gcol, gcr) > 0) {
+      select_.extend(grow, gcol, gcr);        // extend it
       return true;
     } else {
       // TODO: If X,Y outside row/col area and SHIFT down,
@@ -2063,6 +2097,36 @@ bool Fl_Terminal::selection_extend(int X,int Y) {
   return false;
 }
 
+/**
+ Select the word around the given row and column.
+ */
+void Fl_Terminal::select_word(int grow, int gcol) {
+  int i, c0, c1;
+  int r = grow, c = gcol;
+  Utf8Char *row = u8c_ring_row(r);
+  int n = ring_cols();
+  if (c >= n) return;
+  if (row[c].text_utf8()[0]==' ') {
+    for (i=c; i>0; i--) if (row[i-1].text_utf8()[0]!=' ') break;
+    c0 = i;
+    for (i=c; i<n-2; i++) if (row[i+1].text_utf8()[0]!=' ') break;
+    c1 = i;
+  } else {
+    for (i=c; i>0; i--) if (row[i-1].text_utf8()[0]==' ') break;
+    c0 = i;
+    for (i=c; i<n-2; i++) if (row[i+1].text_utf8()[0]==' ') break;
+    c1 = i;
+  }
+  select_.select(r, c0, r, c1);
+}
+
+/**
+ Select the entire row.
+ */
+void Fl_Terminal::select_line(int grow) {
+  select_.select(grow, 0, grow, ring_cols()-1);
+}
+
 /**
   Scroll the display up(+) or down(-) the specified \p rows.
 
@@ -3205,7 +3269,10 @@ void Fl_Terminal::redraw_timer_cb(void *udata) {
   \param[in] X,Y,W,H position and size.
   \param[in] L label string (optional), may be NULL.
 */
-Fl_Terminal::Fl_Terminal(int X,int Y,int W,int H,const char*L) : Fl_Group(X,Y,W,H,L) {
+Fl_Terminal::Fl_Terminal(int X,int Y,int W,int H,const char*L) 
+  : Fl_Group(X,Y,W,H,L),
+    select_(this)
+{
   bool fontsize_defer = false;
   init_(X,Y,W,H,L,-1,-1,100,fontsize_defer);
 }
@@ -3221,7 +3288,10 @@ Fl_Terminal::Fl_Terminal(int X,int Y,int W,int H,const char*L) : Fl_Group(X,Y,W,
   \note fluid uses this constructor internally to avoid font calculations that opens
   the display, useful for when running in a headless context. (issue 837)
 */
-Fl_Terminal::Fl_Terminal(int X,int Y,int W,int H,const char*L,int rows,int cols,int hist) : Fl_Group(X,Y,W,H,L) {
+Fl_Terminal::Fl_Terminal(int X,int Y,int W,int H,const char*L,int rows,int cols,int hist) 
+  : Fl_Group(X,Y,W,H,L),
+    select_(this)
+{
   bool fontsize_defer = true;
   init_(X,Y,W,H,L,rows,cols,hist,fontsize_defer);
 }
@@ -3344,10 +3414,13 @@ void Fl_Terminal::scrollbar_size(int val) {
 
   If the bg color for a character is the special "see through" color 0xffffffff,
   no pixels are drawn.
+
+ \param[in] grow row number
+ \param[in] X, Y top left corner of the row in FLTK coordinates
 */
 void Fl_Terminal::draw_row_bg(int grow, int X, int Y) const {
   int bg_h = current_style_->fontheight();
-  int bg_y = Y - current_style_->fontheight() + current_style_->fontdescent();
+  int bg_y = Y;
   Fl_Color bg_col;
   int pwidth          = 9;
   const Utf8Char *u8c = u8c_ring_row(grow);               // start of spec'd row
@@ -3376,6 +3449,9 @@ void Fl_Terminal::draw_row_bg(int grow, int X, int Y) const {
 /**
   Draw the specified global row, which is the row in ring_chars[].
   The global row includes history + display buffers.
+
+ \param[in] grow row number
+ \param[in] Y top position of characters in the row in FLTK coordinates
 */
 void Fl_Terminal::draw_row(int grow, int Y) const {
   // Draw background color spans, if any
@@ -3383,12 +3459,16 @@ void Fl_Terminal::draw_row(int grow, int Y) const {
   draw_row_bg(grow, X, Y);
 
   // Draw forground text
+  int  baseline = Y + current_style_->fontheight() - current_style_->fontdescent();
   int  scrollval = scrollbar->value();
   int  disp_top = (disp_srow() - scrollval);              // top row we need to view
   int  drow = grow - disp_top;                            // disp row
   bool inside_display = is_disp_ring_row(grow);           // row inside 'display'?
-  int  strikeout_y = Y - (current_style_->fontheight() / 3);
+// This looks better on macOS, but too low for X. Maybe we can get better results using fl_text_extents()?
-  int  underline_y = Y;
+//  int  strikeout_y = baseline - (current_style_->fontheight() / 4);
+//  int  underline_y = baseline + (current_style_->fontheight() / 5);
+  int  strikeout_y = baseline - (current_style_->fontheight() / 3);
+  int  underline_y = baseline;
   const Utf8Char *u8c = u8c_ring_row(grow);
   uchar lastattr = -1;
   bool  is_cursor;
@@ -3406,7 +3486,7 @@ void Fl_Terminal::draw_row(int grow, int Y) const {
     // DRAW CURSOR BLOCK - TODO: support other cursor types?
     if (is_cursor) {
       int cx = X;
-      int cy = Y - cursor_.h() + current_style_->fontdescent();
+      int cy = Y + current_style_->fontheight() - cursor_.h();
       int cw = pwidth;
       int ch = cursor_.h();
       fl_color(cursorbgcolor());
@@ -3428,7 +3508,7 @@ void Fl_Terminal::draw_row(int grow, int Y) const {
       lastattr = -1;                              // (ensure font reset on next iter)
     }
     // 3) Draw text for UTF-8 char. No need to draw spaces
-    if (!u8c->is_char(' ')) fl_draw(u8c->text_utf8(), u8c->length(), X, Y);
+    if (!u8c->is_char(' ')) fl_draw(u8c->text_utf8(), u8c->length(), X, baseline);
     // 4) Strike or underline?
     if (u8c->attrib() & Fl_Terminal::UNDERLINE) fl_line(X, underline_y, X+pwidth, underline_y);
     if (u8c->attrib() & Fl_Terminal::STRIKEOUT) fl_line(X, strikeout_y, X+pwidth, strikeout_y);
@@ -3445,14 +3525,16 @@ void Fl_Terminal::draw_row(int grow, int Y) const {
   depends on what position the scrollbar is set to.
 
   Handles attributes, colors, text selections, cursor.
+
+ \param[in] Y top position of top left character in the window in FLTK coordinates
 */
 void Fl_Terminal::draw_buff(int Y) const {
   int srow = disp_srow() - scrollbar->value();
   int erow = srow + disp_rows();
   const int rowheight = current_style_->fontheight();
   for (int grow=srow; (grow<erow) && (Y<scrn_.b()); grow++) {
-    Y += rowheight;             // advance Y to bottom left corner of row
     draw_row(grow, Y);          // draw global row at Y
+    Y += rowheight;             // advance Y to bottom left corner of row
   }
 }
 
@@ -3499,7 +3581,7 @@ void Fl_Terminal::draw(void) {
   This is used by the constructor to size the row/cols to fit the widget size.
 */
 int Fl_Terminal::w_to_col(int W) const {
-  return int((float(W) / current_style_->charwidth()) + 0.0);    // +.5 overshoots
+  return W / current_style_->charwidth();
 }
 
 /**
@@ -3507,7 +3589,7 @@ int Fl_Terminal::w_to_col(int W) const {
   This is used by the constructor to size the row/cols to fit the widget size.
 */
 int Fl_Terminal::h_to_row(int H) const {
-  return int((float(H) / current_style_->fontheight()) + -0.5);  // +.5 overshoots
+  return H / current_style_->fontheight();
 }
 
 /**
@@ -3555,21 +3637,29 @@ void Fl_Terminal::handle_selection_autoscroll(void) {
   Returns: 1 if 'handled', 0 if not.
 */
 int Fl_Terminal::handle_selection(int e) {
-  int grow=0,gcol=0;
+  int grow=0, gcol=0;
-  bool is_rowcol = (xy_to_glob_rowcol(Fl::event_x(), Fl::event_y(), grow, gcol) > 0)
+  bool gcr = false;
+  bool is_rowcol = (xy_to_glob_rowcol(Fl::event_x(), Fl::event_y(), grow, gcol, gcr) > 0)
                    ? true : false;
   switch (e) {
     case FL_PUSH: {
-      select_.push_rowcol(grow, gcol);
       // SHIFT-LEFT-CLICK? Extend or start new
       if (Fl::event_state(FL_SHIFT)) {
         if (is_selection()) {                           // extend if select in progress
           selection_extend(Fl::event_x(), Fl::event_y());
+          redraw();
           return 1;                                     // express interest in FL_DRAG
         }
       } else {                                          // Start a new selection
+        select_.push_rowcol(grow, gcol, gcr);
         if (select_.clear()) redraw();                  // clear prev selection
-        if (is_rowcol) return 1;                        // express interest in FL_DRAG
+        if (is_rowcol) {
+          switch (Fl::event_clicks()) {
+            case 1: select_word(grow, gcol); break;
+            case 2: select_line(grow); break;
+          }
+          return 1;                    // express interest in FL_DRAG
+        }
       }
       // Left-Click outside terminal area?
       if (!Fl::event_state(FL_SHIFT)) {
@@ -3582,11 +3672,11 @@ int Fl_Terminal::handle_selection(int e) {
     case FL_DRAG: {
       if (is_rowcol) {
         if (!is_selection()) {                          // no selection yet?
-          if (select_.dragged_off(grow, gcol)) {        // dragged off FL_PUSH? enough to start
+          if (select_.dragged_off(grow, gcol, gcr)) {   // dragged off FL_PUSH? enough to start
             select_.start_push();                       // ..start drag with FL_PUSH position
           }
         } else {
-          if (select_.extend(grow, gcol)) redraw();     // redraw if selection changed
+          if (select_.extend(grow, gcol, gcr)) redraw(); // redraw if selection changed
         }
       }
       // If we leave scrn area, start timer to auto-scroll+select
@@ -3594,7 +3684,6 @@ int Fl_Terminal::handle_selection(int e) {
       return 1;
     }
     case FL_RELEASE: {
-      select_.push_clear();
       select_.end();
       // middlemouse gets immediate copy of selection
       if (is_selection()) {