added bubbletea pager

README.md

@@ -23,6 +23,7 @@ Features:
 - history
 - comments (comment character is `#`)
 - variables
+- help screen uses comfortable internal pager
 
 ## Demo
 

calc.go

@@ -78,6 +78,12 @@ erf erfc  erfcinv erfinv exp  exp2 expm1 floor  gamma ilogb j0  j1 log
 log10 log1p log2 logb pow round roundtoeven sin sinh tan tanh trunc y0
 y1 copysign dim hypot
 
+Converter functions:
+cm-to-inch              yards-to-meters         bytes-to-kilobytes
+inch-to-cm              meters-to-yards         bytes-to-megabytes
+gallons-to-liters       miles-to-kilometers     bytes-to-gigabytes
+liters-to-gallons       kilometers-to-miles     bytes-to-terabytes
+
 Batch functions:
 sum                  sum of all values (alias: +)
 max                  max of all values
@@ -579,46 +585,40 @@ func sortcommands(hash Commands) []string {
 }
 
 func (c *Calc) PrintHelp() {
-	fmt.Println("Available configuration commands:")
+	output := "Available configuration commands:\n"
 
 	for _, name := range sortcommands(c.SettingsCommands) {
-		fmt.Printf("%-20s %s\n", name, c.SettingsCommands[name].Help)
+		output += fmt.Sprintf("%-20s %s\n", name, c.SettingsCommands[name].Help)
 	}
 
-	fmt.Println()
-
-	fmt.Println("Available show commands:")
+	output += "\nAvailable show commands:\n"
 
 	for _, name := range sortcommands(c.ShowCommands) {
-		fmt.Printf("%-20s %s\n", name, c.ShowCommands[name].Help)
+		output += fmt.Sprintf("%-20s %s\n", name, c.ShowCommands[name].Help)
 	}
 
-	fmt.Println()
-
-	fmt.Println("Available stack manipulation commands:")
+	output += "\nAvailable stack manipulation commands:\n"
 
 	for _, name := range sortcommands(c.StackCommands) {
-		fmt.Printf("%-20s %s\n", name, c.StackCommands[name].Help)
+		output += fmt.Sprintf("%-20s %s\n", name, c.StackCommands[name].Help)
 	}
 
-	fmt.Println()
-
-	fmt.Println("Other commands:")
+	output += "\nOther commands:\n"
 
 	for _, name := range sortcommands(c.Commands) {
-		fmt.Printf("%-20s %s\n", name, c.Commands[name].Help)
+		output += fmt.Sprintf("%-20s %s\n", name, c.Commands[name].Help)
 	}
 
-	fmt.Println()
-
-	fmt.Println(Help)
+	output += "\n" + Help
 
 	// append lua functions, if any
 	if len(LuaFuncs) > 0 {
-		fmt.Println("Lua functions:")
+		output += "\nLua functions:\n"
 
 		for name, function := range LuaFuncs {
-			fmt.Printf("%-20s %s\n", name, function.help)
+			output += fmt.Sprintf("%-20s %s\n", name, function.help)
 		}
 	}
+
+	Pager(output)
 }

pager.go

@@ -0,0 +1,118 @@
+package main
+
+// pager setup using bubbletea
+// file shamlelessly copied from:
+// https://github.com/charmbracelet/bubbletea/tree/main/examples/pager
+
+import (
+	"fmt"
+	"os"
+	"strings"
+
+	"github.com/charmbracelet/bubbles/viewport"
+	tea "github.com/charmbracelet/bubbletea"
+	"github.com/charmbracelet/lipgloss"
+)
+
+var (
+	titleStyle = func() lipgloss.Style {
+		b := lipgloss.RoundedBorder()
+		b.Right = "├"
+		return lipgloss.NewStyle().BorderStyle(b).Padding(0, 1)
+	}()
+
+	infoStyle = func() lipgloss.Style {
+		b := lipgloss.RoundedBorder()
+		b.Left = "┤"
+		return titleStyle.BorderStyle(b)
+	}()
+)
+
+type model struct {
+	content  string
+	ready    bool
+	viewport viewport.Model
+}
+
+func (m model) Init() tea.Cmd {
+	return nil
+}
+
+func (m model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
+	var (
+		cmd  tea.Cmd
+		cmds []tea.Cmd
+	)
+
+	switch msg := msg.(type) {
+	case tea.KeyMsg:
+		if k := msg.String(); k == "ctrl+c" || k == "q" || k == "esc" {
+			return m, tea.Quit
+		}
+
+	case tea.WindowSizeMsg:
+		headerHeight := lipgloss.Height(m.headerView())
+		footerHeight := lipgloss.Height(m.footerView())
+		verticalMarginHeight := headerHeight + footerHeight
+
+		if !m.ready {
+			// Since this program is using the full size of the viewport we
+			// need to wait until we've received the window dimensions before
+			// we can initialize the viewport. The initial dimensions come in
+			// quickly, though asynchronously, which is why we wait for them
+			// here.
+			m.viewport = viewport.New(msg.Width, msg.Height-verticalMarginHeight)
+			m.viewport.YPosition = headerHeight
+			m.viewport.SetContent(m.content)
+			m.ready = true
+		} else {
+			m.viewport.Width = msg.Width
+			m.viewport.Height = msg.Height - verticalMarginHeight
+		}
+	}
+
+	// Handle keyboard and mouse events in the viewport
+	m.viewport, cmd = m.viewport.Update(msg)
+	cmds = append(cmds, cmd)
+
+	return m, tea.Batch(cmds...)
+}
+
+func (m model) View() string {
+	if !m.ready {
+		return "\n  Initializing..."
+	}
+	return fmt.Sprintf("%s\n%s\n%s", m.headerView(), m.viewport.View(), m.footerView())
+}
+
+func (m model) headerView() string {
+	title := titleStyle.Render("RPN Help Overview")
+	line := strings.Repeat("─", max(0, m.viewport.Width-lipgloss.Width(title)))
+	return lipgloss.JoinHorizontal(lipgloss.Center, title, line)
+}
+
+func (m model) footerView() string {
+	info := infoStyle.Render(fmt.Sprintf("%3.f%%", m.viewport.ScrollPercent()*100))
+	line := strings.Repeat("─", max(0, m.viewport.Width-lipgloss.Width(info)))
+	return lipgloss.JoinHorizontal(lipgloss.Center, line, info)
+}
+
+func max(a, b int) int {
+	if a > b {
+		return a
+	}
+	return b
+}
+
+func Pager(message string) {
+	p := tea.NewProgram(
+		model{content: message},
+		tea.WithAltScreen(),       // use the full size of the terminal in its "alternate screen buffer"
+		tea.WithMouseCellMotion(), // turn on mouse support so we can track the mouse wheel
+	)
+
+	if _, err := p.Run(); err != nil {
+		fmt.Println("could not run pager:", err)
+		os.Exit(1)
+	}
+}