Fix bug where scroll wheel could create duplicate lines on top and bottom

README.md

@@ -1,8 +1,33 @@
-# Tea Party
+# Bubbles
 
-Components for [Tea](https://github.com/charmbraclet/tea)
+Some components for [Bubble Tea](https://github.com/charmbraclet/bubbletea):
 
-⚠️  This project is a pre-release! Check back later.
+* Spinner
+* Text Input
+* Paginator
+* Viewport
+
+## Spinner
+
+A spinner, useful for indicating that some kind of invisible operation is
+happening. There are a couple default ones, but you can also pass your own
+”frames.”
+
+## Text Input
+
+A text input field, akin to an `<input type="text">` in HTML.
+
+## Paginator
+
+A component for handling pagination logic and optionally drawing pagination UI.
+
+## Viewport
+
+A viewport for vertically scrolling content which optionally includes standard
+pager keybindings and mouse wheel support. A high performance mode is available
+for applications which make use of the alterate screen buffer. This is
+generally only necessary when dealing with content with a very large amount of
+ANSI escape sequences.
 
 ## License
 

paginator/paginator.go

@@ -21,17 +21,18 @@ const (
 
 // Model is the Tea model for this user interface.
 type Model struct {
-	Type             Type
-	Page             int
-	PerPage          int
-	TotalPages       int
-	ActiveDot        string
-	InactiveDot      string
-	ArabicFormat     string
-	UseLeftRightKeys bool
-	UseUpDownKeys    bool
-	UseHLKeys        bool
-	UseJKKeys        bool
+	Type              Type
+	Page              int
+	PerPage           int
+	TotalPages        int
+	ActiveDot         string
+	InactiveDot       string
+	ArabicFormat      string
+	UsePgUpPgDownKeys bool
+	UseLeftRightKeys  bool
+	UseUpDownKeys     bool
+	UseHLKeys         bool
+	UseJKKeys         bool
 }
 
 // SetTotalPages is a helper function for calculatng the total number of pages
@@ -98,17 +99,18 @@ func (m Model) OnLastPage() bool {
 // NewModel creates a new model with defaults.
 func NewModel() Model {
 	return Model{
-		Type:             Arabic,
-		Page:             0,
-		PerPage:          1,
-		TotalPages:       1,
-		ActiveDot:        "•",
-		InactiveDot:      "○",
-		ArabicFormat:     "%d/%d",
-		UseLeftRightKeys: true,
-		UseUpDownKeys:    false,
-		UseHLKeys:        true,
-		UseJKKeys:        false,
+		Type:              Arabic,
+		Page:              0,
+		PerPage:           1,
+		TotalPages:        1,
+		ActiveDot:         "•",
+		InactiveDot:       "○",
+		ArabicFormat:      "%d/%d",
+		UsePgUpPgDownKeys: true,
+		UseLeftRightKeys:  true,
+		UseUpDownKeys:     false,
+		UseHLKeys:         true,
+		UseJKKeys:         false,
 	}
 }
 
@@ -116,6 +118,14 @@ func NewModel() Model {
 func Update(msg tea.Msg, m Model) (Model, tea.Cmd) {
 	switch msg := msg.(type) {
 	case tea.KeyMsg:
+		if m.UsePgUpPgDownKeys {
+			switch msg.String() {
+			case "pgup":
+				m.PrevPage()
+			case "pgdown":
+				m.NextPage()
+			}
+		}
 		if m.UseLeftRightKeys {
 			switch msg.String() {
 			case "left":

viewport/viewport.go

@@ -7,6 +7,10 @@ import (
 	tea "github.com/charmbracelet/bubbletea"
 )
 
+const (
+	spacebar = " "
+)
+
 // MODEL
 
 type Model struct {
@@ -53,9 +57,16 @@ func (m Model) AtTop() bool {
 	return m.YOffset <= 0
 }
 
-// AtBottom returns whether or not the viewport is at the very botom position.
+// AtBottom returns whether or not the viewport is at or past the very bottom
+// position.
 func (m Model) AtBottom() bool {
-	return m.YOffset >= len(m.lines)-m.Height-1
+	return m.YOffset >= len(m.lines)-1-m.Height
+}
+
+// PastBottom returns whether or not the viewport is scrolled beyond the last
+// line. This can happen when adjusting the viewport height.
+func (m Model) PastBottom() bool {
+	return m.YOffset > len(m.lines)-1-m.Height
 }
 
 // Scrollpercent returns the amount scrolled as a float between 0 and 1.
@@ -65,7 +76,7 @@ func (m Model) ScrollPercent() float64 {
 	}
 	y := float64(m.YOffset)
 	h := float64(m.Height)
-	t := float64(len(m.lines))
+	t := float64(len(m.lines) - 1)
 	v := y / (t - h)
 	return math.Max(0.0, math.Min(1.0, v))
 }
@@ -95,8 +106,8 @@ func (m *Model) ViewDown() []string {
 	}
 
 	m.YOffset = min(
-		m.YOffset+m.Height,    // target
-		len(m.lines)-m.Height, // fallback
+		m.YOffset+m.Height,      // target
+		len(m.lines)-1-m.Height, // fallback
 	)
 
 	return m.visibleLines()
@@ -123,8 +134,8 @@ func (m *Model) HalfViewDown() (lines []string) {
 	}
 
 	m.YOffset = min(
-		m.YOffset+m.Height/2,  // target
-		len(m.lines)-m.Height, // fallback
+		m.YOffset+m.Height/2,    // target
+		len(m.lines)-1-m.Height, // fallback
 	)
 
 	if len(m.lines) > 0 {
@@ -156,20 +167,26 @@ func (m *Model) HalfViewUp() (lines []string) {
 	return lines
 }
 
-// LineDown moves the view up by the given number of lines.
+// LineDown moves the view down by the given number of lines.
 func (m *Model) LineDown(n int) (lines []string) {
 	if m.AtBottom() || n == 0 {
 		return nil
 	}
 
+	// Make sure the number of lines by which we're going to scroll isn't
+	// greater than the number of lines we actually have left before we reach
+	// the bottom.
+	maxDelta := (len(m.lines) - 1) - (m.YOffset + m.Height) // number of lines - viewport bottom edge
+	n = min(n, maxDelta)
+
 	m.YOffset = min(
-		m.YOffset+n,           // target
-		len(m.lines)-m.Height, // fallback
+		m.YOffset+n,             // target
+		len(m.lines)-1-m.Height, // fallback
 	)
 
 	if len(m.lines) > 0 {
-		top := max(0, m.YOffset+m.Height-n)
-		bottom := min(len(m.lines)-1, m.YOffset+m.Height)
+		top := max(m.YOffset+m.Height-n, 0)
+		bottom := min(m.YOffset+m.Height, len(m.lines)-1)
 		lines = m.lines[top:bottom]
 	}
 
@@ -183,11 +200,45 @@ func (m *Model) LineUp(n int) (lines []string) {
 		return nil
 	}
 
+	// Make sure the number of lines by which we're going to scroll isn't
+	// greater than the number of lines we are from the top.
+	n = min(n, m.YOffset)
+
 	m.YOffset = max(m.YOffset-n, 0)
 
 	if len(m.lines) > 0 {
 		top := max(0, m.YOffset)
-		bottom := min(len(m.lines)-1, m.YOffset+n)
+		bottom := min(m.YOffset+n, len(m.lines)-1)
+		lines = m.lines[top:bottom]
+	}
+
+	return lines
+}
+
+// GotoTop sets the viewport to the top position.
+func (m *Model) GotoTop() (lines []string) {
+	if m.AtTop() {
+		return nil
+	}
+
+	m.YOffset = 0
+
+	if len(m.lines) > 0 {
+		top := m.YOffset
+		bottom := min(m.YOffset+m.Height, len(m.lines)-1)
+		lines = m.lines[top:bottom]
+	}
+
+	return lines
+}
+
+// GotoTop sets the viewport to the bottom position.
+func (m *Model) GotoBottom() (lines []string) {
+	m.YOffset = max(len(m.lines)-1-m.Height, 0)
+
+	if len(m.lines) > 0 {
+		top := m.YOffset
+		bottom := max(len(m.lines)-1, 0)
 		lines = m.lines[top:bottom]
 	}
 
@@ -206,6 +257,8 @@ func Sync(m Model) tea.Cmd {
 		return nil
 	}
 
+	// TODO: we should probably use m.visibleLines() rather than these two
+	// expressions.
 	top := max(m.YOffset, 0)
 	bottom := min(m.YOffset+m.Height, len(m.lines)-1)
 
@@ -216,9 +269,9 @@ func Sync(m Model) tea.Cmd {
 	)
 }
 
-// ViewDown is a high performance command that moves the viewport up by one
-// viewport height. Use Model.ViewDown to get the lines that should be
-// rendered. For example:
+// ViewDown is a high performance command that moves the viewport up by a given
+// numer of lines. Use Model.ViewDown to get the lines that should be rendered.
+// For example:
 //
 //     lines := model.ViewDown(1)
 //     cmd := ViewDown(m, lines)
@@ -230,8 +283,8 @@ func ViewDown(m Model, lines []string) tea.Cmd {
 	return tea.ScrollDown(lines, m.YPosition, m.YPosition+m.Height)
 }
 
-// ViewUp is a high performance command the moves the viewport down by one
-// viewport height. Use Model.ViewDown to get the lines that should be
+// ViewUp is a high performance command the moves the viewport down by a given
+// number of lines height. Use Model.ViewDown to get the lines that should be
 // rendered.
 func ViewUp(m Model, lines []string) tea.Cmd {
 	if len(lines) == 0 {
@@ -240,46 +293,6 @@ func ViewUp(m Model, lines []string) tea.Cmd {
 	return tea.ScrollUp(lines, m.YPosition, m.YPosition+m.Height)
 }
 
-// HalfViewDown is a high performance command the moves the viewport down by
-// half of the height of the viewport. Use Model.HalfViewDown to get the lines
-// that should be rendered.
-func HalfViewDown(m Model, lines []string) tea.Cmd {
-	if len(lines) == 0 {
-		return nil
-	}
-	return tea.ScrollDown(lines, m.YPosition, m.YPosition+m.Height)
-}
-
-// HalfViewUp is a high performance command the moves the viewport up by
-// half of the height of the viewport. Use Model.HalfViewUp to get the lines
-// that should be rendered.
-func HalfViewUp(m Model, lines []string) tea.Cmd {
-	if len(lines) == 0 {
-		return nil
-	}
-	return tea.ScrollUp(lines, m.YPosition, m.YPosition+m.Height)
-}
-
-// LineDown is a high performance command the moves the viewport down by
-// a given number of lines. Use Model.LineDown to get the lines that should be
-// rendered.
-func LineDown(m Model, lines []string) tea.Cmd {
-	if len(lines) == 0 {
-		return nil
-	}
-	return tea.ScrollDown(lines, m.YPosition, m.YPosition+m.Height)
-}
-
-// LineDown is a high performance command the moves the viewport up by a given
-// number of lines. Use Model.LineDown to get the lines that should be
-// rendered.
-func LineUp(m Model, lines []string) tea.Cmd {
-	if len(lines) == 0 {
-		return nil
-	}
-	return tea.ScrollUp(lines, m.YPosition, m.YPosition+m.Height)
-}
-
 // UPDATE
 
 // Update runs the update loop with default keybindings similar to popular
@@ -293,20 +306,14 @@ func Update(msg tea.Msg, m Model) (Model, tea.Cmd) {
 	case tea.KeyMsg:
 		switch msg.String() {
 		// Down one page
-		case "pgdown":
-			fallthrough
-		case " ": // spacebar
-			fallthrough
-		case "f":
+		case "pgdown", spacebar, "f":
 			lines := m.ViewDown()
 			if m.HighPerformanceRendering {
 				cmd = ViewDown(m, lines)
 			}
 
 		// Up one page
-		case "pgup":
-			fallthrough
-		case "b":
+		case "pgup", "b":
 			lines := m.ViewUp()
 			if m.HighPerformanceRendering {
 				cmd = ViewUp(m, lines)
@@ -316,32 +323,28 @@ func Update(msg tea.Msg, m Model) (Model, tea.Cmd) {
 		case "d":
 			lines := m.HalfViewDown()
 			if m.HighPerformanceRendering {
-				cmd = HalfViewDown(m, lines)
+				cmd = ViewDown(m, lines)
 			}
 
 		// Up half page
 		case "u":
 			lines := m.HalfViewUp()
 			if m.HighPerformanceRendering {
-				cmd = HalfViewUp(m, lines)
+				cmd = ViewUp(m, lines)
 			}
 
 		// Down one line
-		case "down":
-			fallthrough
-		case "j":
+		case "down", "j":
 			lines := m.LineDown(1)
 			if m.HighPerformanceRendering {
-				cmd = LineDown(m, lines)
+				cmd = ViewDown(m, lines)
 			}
 
 		// Up one line
-		case "up":
-			fallthrough
-		case "k":
+		case "up", "k":
 			lines := m.LineUp(1)
 			if m.HighPerformanceRendering {
-				cmd = LineUp(m, lines)
+				cmd = ViewUp(m, lines)
 			}
 		}
 
@@ -351,13 +354,13 @@ func Update(msg tea.Msg, m Model) (Model, tea.Cmd) {
 		case tea.MouseWheelUp:
 			lines := m.LineUp(3)
 			if m.HighPerformanceRendering {
-				cmd = LineUp(m, lines)
+				cmd = ViewUp(m, lines)
 			}
 
 		case tea.MouseWheelDown:
 			lines := m.LineDown(3)
 			if m.HighPerformanceRendering {
-				cmd = LineDown(m, lines)
+				cmd = ViewDown(m, lines)
 			}
 		}
 	}