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Fix bug where viewport doesn't render final lines #74

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merged 2 commits into from Sep 17, 2021
Merged

Fix bug where viewport doesn't render final lines #74

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79a6d4b
Fix bug where viewport wouldn't render final lines
meowgorithm Sep 16, 2021
87f2e07
Fix bug where performance rendering could render one line too many
meowgorithm Sep 16, 2021
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143 changes: 44 additions & 99 deletions viewport/viewport.go
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Expand Up @@ -21,7 +21,7 @@ type Model struct {
YOffset int

// YPosition is the position of the viewport in relation to the terminal
// window. It's used in high performance rendering.
// window. It's used in high performance rendering only.
YPosition int

// HighPerformanceRendering bypasses the normal Bubble Tea renderer to
Expand All @@ -45,13 +45,13 @@ func (m Model) AtTop() bool {
// 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)-1-m.Height
return m.YOffset >= len(m.lines)-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
return m.YOffset > len(m.lines)-m.Height
}

// ScrollPercent returns the amount scrolled as a float between 0 and 1.
Expand All @@ -69,15 +69,16 @@ func (m Model) ScrollPercent() float64 {
// SetContent set the pager's text content. For high performance rendering the
// Sync command should also be called.
func (m *Model) SetContent(s string) {
s = strings.Replace(s, "\r\n", "\n", -1) // normalize line endings
s = strings.ReplaceAll(s, "\r\n", "\n") // normalize line endings
m.lines = strings.Split(s, "\n")

if m.YOffset > len(m.lines)-1 {
m.GotoBottom()
}
}

// Return the lines that should currently be visible in the viewport.
// visibleLines returns the lines that should currently be visible in the
// viewport.
func (m Model) visibleLines() (lines []string) {
if len(m.lines) > 0 {
top := max(0, m.YOffset)
Expand All @@ -87,18 +88,29 @@ func (m Model) visibleLines() (lines []string) {
return lines
}

// scrollArea returns the scrollable boundaries for high performance rendering.
func (m Model) scrollArea() (top, bottom int) {
top = max(0, m.YPosition)
bottom = max(top, top+m.Height)
if top > 0 && bottom > top {
bottom--
}
return top, bottom
}

// SetYOffset sets the Y offset.
func (m *Model) SetYOffset(n int) {
m.YOffset = clamp(n, 0, len(m.lines)-m.Height)
}

// ViewDown moves the view down by the number of lines in the viewport.
// Basically, "page down".
func (m *Model) ViewDown() []string {
if m.AtBottom() {
return nil
}

m.YOffset = min(
m.YOffset+m.Height, // target
len(m.lines)-1-m.Height, // fallback
)

m.SetYOffset(m.YOffset + m.Height)
return m.visibleLines()
}

Expand All @@ -108,11 +120,7 @@ func (m *Model) ViewUp() []string {
return nil
}

m.YOffset = max(
m.YOffset-m.Height, // target
0, // fallback
)

m.SetYOffset(m.YOffset - m.Height)
return m.visibleLines()
}

Expand All @@ -122,18 +130,8 @@ func (m *Model) HalfViewDown() (lines []string) {
return nil
}

m.YOffset = min(
m.YOffset+m.Height/2, // target
len(m.lines)-1-m.Height, // fallback
)

if len(m.lines) > 0 {
top := max(m.YOffset+m.Height/2, 0)
bottom := clamp(m.YOffset+m.Height, top, len(m.lines)-1)
lines = m.lines[top:bottom]
}

return lines
m.SetYOffset(m.YOffset + m.Height/2)
return m.visibleLines()
}

// HalfViewUp moves the view up by half the height of the viewport.
Expand All @@ -142,18 +140,8 @@ func (m *Model) HalfViewUp() (lines []string) {
return nil
}

m.YOffset = max(
m.YOffset-m.Height/2, // target
0, // fallback
)

if len(m.lines) > 0 {
top := max(m.YOffset, 0)
bottom := clamp(m.YOffset+m.Height/2, top, len(m.lines)-1)
lines = m.lines[top:bottom]
}

return lines
m.SetYOffset(m.YOffset - m.Height/2)
return m.visibleLines()
}

// LineDown moves the view down by the given number of lines.
Expand All @@ -165,21 +153,8 @@ func (m *Model) LineDown(n int) (lines []string) {
// 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)-1-m.Height, // fallback
)

if len(m.lines) > 0 {
top := max(m.YOffset+m.Height-n, 0)
bottom := clamp(m.YOffset+m.Height, top, len(m.lines)-1)
lines = m.lines[top:bottom]
}

return lines
m.SetYOffset(m.YOffset + n)
return m.visibleLines()
}

// LineUp moves the view down by the given number of lines. Returns the new
Expand All @@ -191,17 +166,8 @@ func (m *Model) LineUp(n int) (lines []string) {

// 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 := clamp(m.YOffset+n, top, len(m.lines)-1)
lines = m.lines[top:bottom]
}

return lines
m.SetYOffset(m.YOffset - n)
return m.visibleLines()
}

// GotoTop sets the viewport to the top position.
Expand All @@ -210,28 +176,14 @@ func (m *Model) GotoTop() (lines []string) {
return nil
}

m.YOffset = 0

if len(m.lines) > 0 {
top := m.YOffset
bottom := clamp(m.YOffset+m.Height, top, len(m.lines)-1)
lines = m.lines[top:bottom]
}

return lines
m.SetYOffset(0)
return m.visibleLines()
}

// GotoBottom 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]
}

return lines
m.SetYOffset(len(m.lines) - 1 - m.Height)
return m.visibleLines()
}

// COMMANDS
Expand All @@ -245,17 +197,8 @@ func Sync(m Model) tea.Cmd {
if len(m.lines) == 0 {
return nil
}

// TODO: we should probably use m.visibleLines() rather than these two
// expressions.
top := max(m.YOffset, 0)
bottom := clamp(m.YOffset+m.Height, 0, len(m.lines)-1)

return tea.SyncScrollArea(
m.lines[top:bottom],
m.YPosition,
m.YPosition+m.Height,
)
top, bottom := m.scrollArea()
return tea.SyncScrollArea(m.visibleLines(), top, bottom)
}

// ViewDown is a high performance command that moves the viewport up by a given
Expand All @@ -269,7 +212,8 @@ func ViewDown(m Model, lines []string) tea.Cmd {
if len(lines) == 0 {
return nil
}
return tea.ScrollDown(lines, m.YPosition, m.YPosition+m.Height)
top, bottom := m.scrollArea()
return tea.ScrollDown(lines, top, bottom)
}

// ViewUp is a high performance command the moves the viewport down by a given
Expand All @@ -279,7 +223,8 @@ func ViewUp(m Model, lines []string) tea.Cmd {
if len(lines) == 0 {
return nil
}
return tea.ScrollUp(lines, m.YPosition, m.YPosition+m.Height)
top, bottom := m.scrollArea()
return tea.ScrollUp(lines, top, bottom)
}

// UPDATE
Expand Down Expand Up @@ -360,8 +305,8 @@ func (m Model) Update(msg tea.Msg) (Model, tea.Cmd) {
// View renders the viewport into a string.
func (m Model) View() string {
if m.HighPerformanceRendering {
// Just send newlines since we're doing to be rendering the actual
// content seprately. We still need send something that equals the
// Just send newlines since we're going to be rendering the actual
// content seprately. We still need to send something that equals the
// height of this view so that the Bubble Tea standard renderer can
// position anything below this view properly.
return strings.Repeat("\n", m.Height-1)
Expand All @@ -372,7 +317,7 @@ func (m Model) View() string {
// Fill empty space with newlines
extraLines := ""
if len(lines) < m.Height {
extraLines = strings.Repeat("\n", m.Height-len(lines))
extraLines = strings.Repeat("\n", max(0, m.Height-len(lines)))
}

return strings.Join(lines, "\n") + extraLines
Expand Down