From 737e4cdbd35cd23ad2e747bbbfad44cd6a176698 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Thu, 27 Jul 2023 08:40:19 +0530
Subject: [PATCH] unicode_input kitten: Fix scrolling over multiple screens not
 working

Fixes #6497
---
 docs/changelog.rst             |  2 ++
 kittens/unicode_input/table.go | 48 ++++++++++++++++++++--------------
 2 files changed, 31 insertions(+), 19 deletions(-)

diff --git a/docs/changelog.rst b/docs/changelog.rst
index c4ea959bb..87ff13afb 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -44,6 +44,8 @@ Detailed list of changes
 
 - Detect .tex and Makefiles as plain text files (:iss:`6492`)
 
+- unicode_input kitten: Fix scrolling over multiple screens not working (:iss:`6497`)
+
 0.29.1 [2023-07-17]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
diff --git a/kittens/unicode_input/table.go b/kittens/unicode_input/table.go
index f73b3739f..904bc08f1 100644
--- a/kittens/unicode_input/table.go
+++ b/kittens/unicode_input/table.go
@@ -51,15 +51,21 @@ func ljust(s string, sz int) string {
 	return s
 }
 
+type scroll_data struct {
+	num_items_per_page int
+	scroll_rows        int
+}
+
 type table struct {
-	emoji_variation          string
-	layout_dirty             bool
-	last_rows, last_cols     int
-	codepoints               []rune
-	current_idx, scroll_rows int
-	text                     string
-	num_cols, num_rows       int
-	mode                     Mode
+	emoji_variation      string
+	layout_dirty         bool
+	last_rows, last_cols int
+	codepoints           []rune
+	current_idx          int
+	scroll_data          scroll_data
+	text                 string
+	num_cols, num_rows   int
+	mode                 Mode
 
 	green, reversed, intense_gray func(...any) string
 }
@@ -81,6 +87,7 @@ func (self *table) current_codepoint() rune {
 }
 
 func (self *table) set_codepoints(codepoints []rune, mode Mode, current_idx int) {
+	delta := len(codepoints) - len(self.codepoints)
 	self.codepoints = codepoints
 	if self.codepoints != nil && mode != FAVORITES && mode != HEX {
 		slices.Sort(self.codepoints)
@@ -93,7 +100,9 @@ func (self *table) set_codepoints(codepoints []rune, mode Mode, current_idx int)
 	if self.current_idx >= len(self.codepoints) {
 		self.current_idx = 0
 	}
-	self.scroll_rows = 0
+	if delta != 0 {
+		self.scroll_data = scroll_data{}
+	}
 }
 
 func (self *table) codepoint_at_hint(hint string) rune {
@@ -201,7 +210,10 @@ func (self *table) layout(rows, cols int) string {
 	space_for_desc = col_width - 2 - idx_size - 4
 	self.num_rows = rows
 	rows_left := rows
-	skip_scroll := self.scroll_rows * self.num_cols
+	if self.scroll_data.num_items_per_page != self.num_cols*self.num_rows {
+		self.update_scroll_data()
+	}
+	skip_scroll := self.scroll_data.scroll_rows * self.num_cols
 
 	for i, cd := range parts {
 		if skip_scroll > 0 {
@@ -223,6 +235,12 @@ func (self *table) layout(rows, cols int) string {
 	return self.text
 }
 
+func (self *table) update_scroll_data() {
+	self.scroll_data.num_items_per_page = self.num_rows * self.num_cols
+	page_num := self.current_idx / self.scroll_data.num_items_per_page
+	self.scroll_data.scroll_rows = self.num_rows * page_num
+}
+
 func (self *table) move_current(rows, cols int) {
 	if len(self.codepoints) == 0 {
 		return
@@ -237,13 +255,5 @@ func (self *table) move_current(rows, cols int) {
 		self.current_idx = utils.Max(0, utils.Min(self.current_idx, len(self.codepoints)-1))
 		self.layout_dirty = true
 	}
-	first_visible := self.scroll_rows * self.num_cols
-	last_visible := first_visible + ((self.num_cols * self.num_rows) - 1)
-	scroll_amount := self.num_rows
-	if self.current_idx < first_visible {
-		self.scroll_rows = utils.Max(self.scroll_rows-scroll_amount, 0)
-	}
-	if self.current_idx > last_visible {
-		self.scroll_rows += scroll_amount
-	}
+	self.update_scroll_data()
 }