From 260249491d2301e3e2bf9d2d0935ccb23c41d491 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Sun, 16 Oct 2022 12:20:27 +0530
Subject: [PATCH] Avoid Querying screen size on every resize

---
 tools/cmd/at/shell.go      |  5 +----
 tools/tui/readline/api.go  | 12 +++++++++++-
 tools/tui/readline/draw.go | 14 ++++++++------
 3 files changed, 20 insertions(+), 11 deletions(-)

diff --git a/tools/cmd/at/shell.go b/tools/cmd/at/shell.go
index 1c5258d39..7ab1e807e 100644
--- a/tools/cmd/at/shell.go
+++ b/tools/cmd/at/shell.go
@@ -47,10 +47,7 @@ func shell_loop(rl *readline.Readline, kill_if_signaled bool) (int, error) {
 		return nil
 	}
 
-	lp.OnResize = func(old_size loop.ScreenSize, new_size loop.ScreenSize) error {
-		rl.Redraw()
-		return nil
-	}
+	lp.OnResize = rl.OnResize
 
 	lp.OnKeyEvent = func(event *loop.KeyEvent) error {
 		err := rl.OnKeyEvent(event)
diff --git a/tools/tui/readline/api.go b/tools/tui/readline/api.go
index f2e900493..a8ab8d725 100644
--- a/tools/tui/readline/api.go
+++ b/tools/tui/readline/api.go
@@ -59,7 +59,8 @@ type Readline struct {
 	history                 *History
 
 	// The number of lines after the initial line on the screen
-	cursor_y int
+	cursor_y     int
+	screen_width int
 	// Input lines
 	lines []string
 	// The cursor position in the text
@@ -172,3 +173,12 @@ func (self *Readline) AllText() string {
 func (self *Readline) CursorAtEndOfLine() bool {
 	return self.cursor.X >= len(self.lines[self.cursor.Y])
 }
+
+func (self *Readline) OnResize(old_size loop.ScreenSize, new_size loop.ScreenSize) error {
+	self.screen_width = int(new_size.CellWidth)
+	if self.screen_width < 1 {
+		self.screen_width = 1
+	}
+	self.Redraw()
+	return nil
+}
diff --git a/tools/tui/readline/draw.go b/tools/tui/readline/draw.go
index 6f77b0e45..f407536c5 100644
--- a/tools/tui/readline/draw.go
+++ b/tools/tui/readline/draw.go
@@ -29,7 +29,7 @@ func (self *Readline) move_cursor_to_text_position(pos, screen_width int) int {
 	return num_of_lines
 }
 
-func (self *Readline) current_screen_size() (int, int) {
+func (self *Readline) update_current_screen_size() {
 	screen_size, err := self.loop.ScreenSize()
 	if err != nil {
 		screen_size.WidthCells = 80
@@ -41,12 +41,14 @@ func (self *Readline) current_screen_size() (int, int) {
 	if screen_size.HeightCells < 1 {
 		screen_size.HeightCells = 1
 	}
-	return int(screen_size.WidthCells), int(screen_size.HeightCells)
+	self.screen_width = int(screen_size.WidthCells)
 }
 
 func (self *Readline) redraw() {
-	screen_width, _ := self.current_screen_size()
-	if screen_width < 4 {
+	if self.screen_width == 0 {
+		self.update_current_screen_size()
+	}
+	if self.screen_width < 4 {
 		return
 	}
 	if self.cursor_y > 0 {
@@ -66,7 +68,7 @@ func (self *Readline) redraw() {
 		if i == self.cursor.Y {
 			line_with_cursor = y
 		}
-		y += self.write_line_with_prompt(line, p, screen_width)
+		y += self.write_line_with_prompt(line, p, self.screen_width)
 	}
 	self.loop.MoveCursorVertically(-y + line_with_cursor)
 	line := self.lines[self.cursor.Y]
@@ -74,6 +76,6 @@ func (self *Readline) redraw() {
 	if self.cursor.Y > 0 {
 		plen = self.continuation_prompt_len
 	}
-	line_with_cursor += self.move_cursor_to_text_position(plen+wcswidth.Stringwidth(line[:self.cursor.X]), screen_width)
+	line_with_cursor += self.move_cursor_to_text_position(plen+wcswidth.Stringwidth(line[:self.cursor.X]), self.screen_width)
 	self.cursor_y = line_with_cursor
 }