More work on mouse selection in the diff kitten

kittens/diff/mouse.go

@@ -14,8 +14,15 @@ import (
 
 var _ = fmt.Print
 
+type SelectionBoundary struct {
+	line ScrollPos
+	x    int
+}
+
 type MouseSelection struct {
-	start_line, end_line ScrollPos
+	start, end   SelectionBoundary
+	is_active    bool
+	min_x, max_x int
 }
 
 type KittyOpts struct {
@@ -52,10 +59,63 @@ func (self *Handler) handle_wheel_event(up bool) {
 }
 
 func (self *Handler) start_mouse_selection(ev *loop.MouseEvent) {
+	self.mouse_selection = MouseSelection{}
+	ms := &self.mouse_selection
+	available_cols := self.logical_lines.columns / 2
+	if ev.Cell.Y >= self.screen_size.num_lines || ev.Cell.X < self.logical_lines.margin_size || (ev.Cell.X >= available_cols && ev.Cell.X < available_cols+self.logical_lines.margin_size) {
+		return
+	}
+	pos := self.scroll_pos
+	self.logical_lines.IncrementScrollPosBy(&pos, ev.Cell.Y)
+	ll := self.logical_lines.At(pos.logical_line)
+	if ll.line_type == EMPTY_LINE || ll.line_type == IMAGE_LINE {
+		return
+	}
+	ms.start.line = pos
+
+	ms.start.x = ev.Cell.X
+	ms.min_x = self.logical_lines.margin_size
+	ms.max_x = available_cols - 1
+	if ms.start.x >= available_cols {
+		ms.min_x += available_cols
+		ms.max_x += available_cols
+	}
+	ms.start.x = utils.Max(ms.min_x, utils.Min(ms.start.x, ms.max_x))
+
+	ms.end = ms.start
+	ms.is_active = true
 }
 
 func (self *Handler) update_mouse_selection(ev *loop.MouseEvent) {
+	ms := &self.mouse_selection
+	if !self.mouse_selection.is_active {
+		return
+	}
+	pos := self.scroll_pos
+	y := ev.Cell.Y
+	y = utils.Max(0, utils.Min(y, self.screen_size.num_lines-1))
+	self.logical_lines.IncrementScrollPosBy(&pos, y)
+	ms.end.x = ev.Cell.X
+	ms.end.x = utils.Max(ms.min_x, utils.Min(ms.end.x, ms.max_x))
+	ms.end.line = pos
+}
+
+func (self *Handler) clear_mouse_selection() {
+	self.mouse_selection = MouseSelection{}
 }
 
 func (self *Handler) finish_mouse_selection(ev *loop.MouseEvent) {
+	self.update_mouse_selection(ev)
+	ms := &self.mouse_selection
+	if !self.mouse_selection.is_active {
+		return
+	}
+	ms.is_active = false
+}
+
+func (self *Handler) add_mouse_selection_to_line(line string, line_pos ScrollPos) {
+	ms := &self.mouse_selection
+	if !ms.is_active {
+		return
+	}
 }