More work on porting themes UI to Go

tools/cmd/themes/list.go

@@ -0,0 +1,49 @@
+// License: GPLv3 Copyright: 2023, Kovid Goyal, <kovid at kovidgoyal.net>
+
+package themes
+
+import (
+	"fmt"
+
+	"kitty/tools/themes"
+)
+
+var _ = fmt.Print
+
+type ThemesList struct {
+	themes, all_themes     *themes.Themes
+	current_search         string
+	display_strings        []string
+	widths                 []int
+	max_width, current_idx int
+}
+
+func (self *ThemesList) Len() int {
+	if self.themes == nil {
+		return 0
+	}
+	return self.themes.Len()
+}
+
+func (self *ThemesList) Next(delta int, allow_wrapping bool) bool {
+	if len(self.display_strings) == 0 {
+		return false
+	}
+	idx := self.current_idx + delta
+	if !allow_wrapping && (idx < 0 || idx > self.Len()) {
+		return false
+	}
+	for idx < 0 {
+		idx += self.Len()
+	}
+	self.current_idx = idx % self.Len()
+	return true
+}
+
+func (self *ThemesList) UpdateThemes(themes *themes.Themes) {
+	self.themes, self.all_themes = themes, themes
+	if self.current_search != "" {
+		self.themes = self.all_themes.Copy()
+	} else {
+	}
+}