2020-05-26 02:57:58 +03:00
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package viewport
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import (
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2020-06-16 00:50:13 +03:00
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"os"
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"strings"
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tea "github.com/charmbracelet/bubbletea"
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)
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// MODEL
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type Model struct {
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Err error
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Width int
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Height int
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// YOffset is the vertical scroll position.
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YOffset int
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// Y is the position of the viewport in relation to the terminal window.
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// It's used in high performance rendering.
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Y int
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2020-06-16 23:10:34 +03:00
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// UseInternalRenderer specifies whether or not to use the pager's
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// internal, high performance renderer to paint the screen.
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UseInternalRenderer bool
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lines []string
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r renderer
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}
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func NewModel(yPos, width, height, terminalWidth, terminalHeight int) Model {
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return Model{
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Width: width,
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Height: height,
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UseInternalRenderer: true,
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r: renderer{
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Y: yPos,
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Height: height,
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TerminalWidth: terminalWidth,
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TerminalHeight: terminalHeight,
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Out: os.Stdout,
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},
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}
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}
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// AtTop returns whether or not the viewport is in the very top position.
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func (m Model) AtTop() bool {
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return m.YOffset <= 0
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}
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// AtBottom returns whether or not the viewport is at the very botom position.
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func (m Model) AtBottom() bool {
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return m.YOffset >= len(m.lines)-m.Height-1
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}
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// Scrollpercent returns the amount scrolled as a float between 0 and 1.
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func (m Model) ScrollPercent() float64 {
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if m.Height >= len(m.lines) {
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return 1.0
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}
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y := float64(m.YOffset)
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h := float64(m.Height)
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t := float64(len(m.lines))
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return y / (t - h)
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}
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// SetContent set the pager's text content.
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func (m *Model) SetContent(s string) {
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s = strings.Replace(s, "\r\n", "\n", -1) // normalize line endings
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m.lines = strings.Split(s, "\n")
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if m.UseInternalRenderer {
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top := max(m.YOffset, 0)
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bottom := min(m.YOffset+m.Height, len(m.lines))
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m.r.sync(m.lines[top:bottom])
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}
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}
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// ViewDown moves the view down by the number of lines in the viewport.
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// Basically, "page down".
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func (m *Model) ViewDown() {
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if m.AtBottom() {
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return
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}
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if m.UseInternalRenderer {
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top := max(m.YOffset+m.Height, 0)
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bottom := min(top+m.Height, len(m.lines)-1)
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m.r.insertBottom(m.lines[top:bottom])
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}
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m.YOffset = min(
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m.YOffset+m.Height, // target
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len(m.lines)-m.Height, // fallback
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)
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}
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// ViewUp moves the view up by one height of the viewport. Basically, "page up".
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func (m *Model) ViewUp() {
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if m.AtTop() {
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return
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}
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if m.UseInternalRenderer {
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top := max(m.YOffset-m.Height, 0)
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bottom := min(m.YOffset, len(m.lines))
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m.r.insertTop(m.lines[top:bottom])
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}
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m.YOffset = max(
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m.YOffset-m.Height, // target
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0, // fallback
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)
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}
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// HalfViewDown moves the view down by half the height of the viewport.
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func (m *Model) HalfViewDown() {
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if m.AtBottom() {
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return
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}
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if m.UseInternalRenderer {
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top := max(m.YOffset+m.Height/2, 0)
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bottom := min(top+m.Height, len(m.lines)-1)
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m.r.insertBottom(m.lines[top:bottom])
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}
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m.YOffset = min(
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m.YOffset+m.Height/2, // target
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len(m.lines)-m.Height, // fallback
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)
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}
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// HalfViewUp moves the view up by half the height of the viewport.
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func (m *Model) HalfViewUp() {
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if m.AtTop() {
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return
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}
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if m.UseInternalRenderer {
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top := max(m.YOffset-m.Height/2, 0)
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bottom := clamp(m.YOffset, top, len(m.lines))
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m.r.insertTop(m.lines[top:bottom])
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}
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m.YOffset = max(
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m.YOffset-m.Height/2, // target
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0, // fallback
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)
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}
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// LineDown moves the view up by the given number of lines.
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func (m *Model) LineDown(n int) {
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if m.AtBottom() || n == 0 {
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return
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}
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if m.UseInternalRenderer {
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bottom := min(m.YOffset+m.Height+n, len(m.lines))
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top := max(bottom-n, 0)
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m.r.insertBottom(m.lines[top:bottom])
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}
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m.YOffset = min(
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m.YOffset+n, // target
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len(m.lines)-m.Height, // fallback
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)
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}
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// LineUp moves the view down by the given number of lines.
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func (m *Model) LineUp(n int) {
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if m.AtTop() || n == 0 {
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return
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}
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if m.UseInternalRenderer {
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top := max(m.YOffset-n, 0)
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bottom := min(top+n, len(m.lines))
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m.r.insertTop(m.lines[top:bottom])
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}
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m.YOffset = max(m.YOffset-n, 0)
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}
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// UPDATE
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// Update runs the update loop with default keybindings. To define your own
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// keybindings use the methods on Model and define your own update function.
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func Update(msg tea.Msg, m Model) (Model, tea.Cmd) {
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switch msg := msg.(type) {
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case tea.KeyMsg:
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switch msg.String() {
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// Down one page
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case "pgdown":
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fallthrough
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case " ": // spacebar
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fallthrough
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case "f":
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m.ViewDown()
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return m, nil
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// Up one page
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case "pgup":
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fallthrough
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case "b":
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m.ViewUp()
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return m, nil
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// Down half page
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case "d":
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m.HalfViewDown()
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return m, nil
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// Up half page
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case "u":
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m.HalfViewUp()
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return m, nil
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// Down one line
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case "down":
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fallthrough
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case "j":
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m.LineDown(1)
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return m, nil
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// Up one line
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case "up":
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fallthrough
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case "k":
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m.LineUp(1)
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return m, nil
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}
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}
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return m, nil
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}
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// VIEW
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// View renders the viewport into a string.
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func View(m Model) string {
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if m.UseInternalRenderer {
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// Skip over the area that would normally be rendered
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return cursorDownString(m.Height)
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}
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if m.Err != nil {
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return m.Err.Error()
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}
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var lines []string
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if len(m.lines) > 0 {
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top := max(0, m.YOffset)
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bottom := min(len(m.lines), m.YOffset+m.Height)
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lines = m.lines[top:bottom]
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}
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// Fill empty space with newlines
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extraLines := ""
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if len(lines) < m.Height {
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extraLines = strings.Repeat("\n", m.Height-len(lines))
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}
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return strings.Join(lines, "\n") + extraLines
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}
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// ETC
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func min(a, b int) int {
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if a < b {
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return a
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}
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return b
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}
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func max(a, b int) int {
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if a > b {
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return a
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}
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return b
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}
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func clamp(val, low, high int) int {
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return max(low, min(high, val))
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}
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