From d19f28f2b4e5950bb5ab287280274bae129b30d2 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Mon, 27 Mar 2023 21:23:31 +0530
Subject: [PATCH] More work on mouse selection in the diff kitten

---
 kittens/diff/mouse.go | 62 ++++++++++++++++++++++++++++++++++++++++++-
 kittens/diff/ui.go    |  4 +++
 2 files changed, 65 insertions(+), 1 deletion(-)

diff --git a/kittens/diff/mouse.go b/kittens/diff/mouse.go
index ae96b049c..81d334a8a 100644
--- a/kittens/diff/mouse.go
+++ b/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
+	}
 }
diff --git a/kittens/diff/ui.go b/kittens/diff/ui.go
index 3f2b30ded..8bf57048c 100644
--- a/kittens/diff/ui.go
+++ b/kittens/diff/ui.go
@@ -249,6 +249,7 @@ func (self *Handler) handle_async_result(r AsyncResult) error {
 	case DIFF:
 		self.diff_map = r.diff_map
 		self.calculate_statistics()
+		self.clear_mouse_selection()
 		err := self.render_diff()
 		if err != nil {
 			return err
@@ -272,6 +273,7 @@ func (self *Handler) handle_async_result(r AsyncResult) error {
 }
 
 func (self *Handler) on_resize(old_size, new_size loop.ScreenSize) error {
+	self.clear_mouse_selection()
 	self.update_screen_size(new_size)
 	if self.diff_map != nil && self.collection != nil {
 		err := self.render_diff()
@@ -352,6 +354,7 @@ func (self *Handler) draw_screen() {
 		if self.current_search != nil {
 			sl = self.current_search.markup_line(sl, pos)
 		}
+		self.add_mouse_selection_to_line(sl, pos)
 		lp.QueueWriteString(sl)
 		lp.MoveCursorVertically(1)
 		lp.QueueWriteString("\x1b[m\r")
@@ -543,6 +546,7 @@ func (self *Handler) change_context_count(val int) bool {
 	self.current_context_count = val
 	p := self.scroll_pos
 	self.restore_position = &p
+	self.clear_mouse_selection()
 	self.generate_diff()
 	self.draw_screen()
 	return true