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feat(render): remove flickering #1132

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feat(render): remove flickering #1132

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1946b9b
feat(render): remove flickering
LeperGnome Sep 7, 2024
d811f19
feat(render): update tests for non-flick rendering + optimisations
LeperGnome Sep 7, 2024
4c662ec
feat(render): fix typo
LeperGnome Sep 8, 2024
e7fdeda
Merge branch 'charmbracelet:main' into no-flick-render
LeperGnome Sep 14, 2024
990a85a
update golden output
LeperGnome Sep 15, 2024
5c8831f
Merge branch 'charmbracelet:main' into no-flick-render
LeperGnome Sep 16, 2024
e7d8095
feat(render): upd EraseDisplayRight
LeperGnome Sep 16, 2024
1320148
Merge branch 'charmbracelet:main' into no-flick-render
LeperGnome Sep 17, 2024
1237126
feat(render): skipping lines from previous frame
LeperGnome Sep 18, 2024
4410eb2
Merge branch 'charmbracelet:main' into no-flick-render
LeperGnome Sep 20, 2024
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8 changes: 4 additions & 4 deletions examples/simple/testdata/TestApp.golden
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
[?25l[?2004hHi. This program will exit in 10 seconds.

To quit sooner press ctrl-c, or press ctrl-z to suspend...
Hi. This program will exit in 9 seconds.
[?25l[?2004hHi. This program will exit in 10 seconds.

To quit sooner press ctrl-c, or press ctrl-z to suspend...
Hi. This program will exit in 9 seconds.
[?2004l[?25h[?1002l[?1003l[?1006l
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18 changes: 9 additions & 9 deletions screen_test.go
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -14,47 +14,47 @@ func TestClearMsg(t *testing.T) {
{
name: "clear_screen",
cmds: []Cmd{ClearScreen},
expected: "\x1b[?25l\x1b[?2004h\x1b[2J\x1b[1;1H\rsuccess\r\n\x1b[D\x1b[2K\r\x1b[?2004l\x1b[?25h\x1b[?1002l\x1b[?1003l\x1b[?1006l",
expected: "\x1b[?25l\x1b[?2004h\x1b[2J\x1b[1;1H\rsuccess\x1b[0K\r\n\x1b[0K\x1b[D\x1b[2K\r\x1b[?2004l\x1b[?25h\x1b[?1002l\x1b[?1003l\x1b[?1006l",
},
{
name: "altscreen",
cmds: []Cmd{EnterAltScreen, ExitAltScreen},
expected: "\x1b[?25l\x1b[?2004h\x1b[?1049h\x1b[2J\x1b[1;1H\x1b[?25l\x1b[?1049l\x1b[?25l\rsuccess\r\n\x1b[D\x1b[2K\r\x1b[?2004l\x1b[?25h\x1b[?1002l\x1b[?1003l\x1b[?1006l",
expected: "\x1b[?25l\x1b[?2004h\x1b[?1049h\x1b[2J\x1b[1;1H\x1b[?25l\x1b[?1049l\x1b[?25l\rsuccess\x1b[0K\r\n\x1b[0K\x1b[D\x1b[2K\r\x1b[?2004l\x1b[?25h\x1b[?1002l\x1b[?1003l\x1b[?1006l",
},
{
name: "altscreen_autoexit",
cmds: []Cmd{EnterAltScreen},
expected: "\x1b[?25l\x1b[?2004h\x1b[?1049h\x1b[2J\x1b[1;1H\x1b[?25l\rsuccess\r\n\x1b[2;0H\x1b[2K\r\x1b[?2004l\x1b[?25h\x1b[?1002l\x1b[?1003l\x1b[?1006l\x1b[?1049l\x1b[?25h",
expected: "\x1b[?25l\x1b[?2004h\x1b[?1049h\x1b[2J\x1b[1;1H\x1b[?25l\rsuccess\x1b[0K\r\n\x1b[0K\x1b[2;0H\x1b[2K\r\x1b[?2004l\x1b[?25h\x1b[?1002l\x1b[?1003l\x1b[?1006l\x1b[?1049l\x1b[?25h",
},
{
name: "mouse_cellmotion",
cmds: []Cmd{EnableMouseCellMotion},
expected: "\x1b[?25l\x1b[?2004h\x1b[?1002h\x1b[?1006h\rsuccess\r\n\x1b[D\x1b[2K\r\x1b[?2004l\x1b[?25h\x1b[?1002l\x1b[?1003l\x1b[?1006l",
expected: "\x1b[?25l\x1b[?2004h\x1b[?1002h\x1b[?1006h\rsuccess\x1b[0K\r\n\x1b[0K\x1b[D\x1b[2K\r\x1b[?2004l\x1b[?25h\x1b[?1002l\x1b[?1003l\x1b[?1006l",
},
{
name: "mouse_allmotion",
cmds: []Cmd{EnableMouseAllMotion},
expected: "\x1b[?25l\x1b[?2004h\x1b[?1003h\x1b[?1006h\rsuccess\r\n\x1b[D\x1b[2K\r\x1b[?2004l\x1b[?25h\x1b[?1002l\x1b[?1003l\x1b[?1006l",
expected: "\x1b[?25l\x1b[?2004h\x1b[?1003h\x1b[?1006h\rsuccess\x1b[0K\r\n\x1b[0K\x1b[D\x1b[2K\r\x1b[?2004l\x1b[?25h\x1b[?1002l\x1b[?1003l\x1b[?1006l",
},
{
name: "mouse_disable",
cmds: []Cmd{EnableMouseAllMotion, DisableMouse},
expected: "\x1b[?25l\x1b[?2004h\x1b[?1003h\x1b[?1006h\x1b[?1002l\x1b[?1003l\x1b[?1006l\rsuccess\r\n\x1b[D\x1b[2K\r\x1b[?2004l\x1b[?25h\x1b[?1002l\x1b[?1003l\x1b[?1006l",
expected: "\x1b[?25l\x1b[?2004h\x1b[?1003h\x1b[?1006h\x1b[?1002l\x1b[?1003l\x1b[?1006l\rsuccess\x1b[0K\r\n\x1b[0K\x1b[D\x1b[2K\r\x1b[?2004l\x1b[?25h\x1b[?1002l\x1b[?1003l\x1b[?1006l",
},
{
name: "cursor_hide",
cmds: []Cmd{HideCursor},
expected: "\x1b[?25l\x1b[?2004h\x1b[?25l\rsuccess\r\n\x1b[D\x1b[2K\r\x1b[?2004l\x1b[?25h\x1b[?1002l\x1b[?1003l\x1b[?1006l",
expected: "\x1b[?25l\x1b[?2004h\x1b[?25l\rsuccess\x1b[0K\r\n\x1b[0K\x1b[D\x1b[2K\r\x1b[?2004l\x1b[?25h\x1b[?1002l\x1b[?1003l\x1b[?1006l",
},
{
name: "cursor_hideshow",
cmds: []Cmd{HideCursor, ShowCursor},
expected: "\x1b[?25l\x1b[?2004h\x1b[?25l\x1b[?25h\rsuccess\r\n\x1b[D\x1b[2K\r\x1b[?2004l\x1b[?25h\x1b[?1002l\x1b[?1003l\x1b[?1006l",
expected: "\x1b[?25l\x1b[?2004h\x1b[?25l\x1b[?25h\rsuccess\x1b[0K\r\n\x1b[0K\x1b[D\x1b[2K\r\x1b[?2004l\x1b[?25h\x1b[?1002l\x1b[?1003l\x1b[?1006l",
},
{
name: "bp_stop_start",
cmds: []Cmd{DisableBracketedPaste, EnableBracketedPaste},
expected: "\x1b[?25l\x1b[?2004h\x1b[?2004l\x1b[?2004h\rsuccess\r\n\x1b[D\x1b[2K\r\x1b[?2004l\x1b[?25h\x1b[?1002l\x1b[?1003l\x1b[?1006l",
expected: "\x1b[?25l\x1b[?2004h\x1b[?2004l\x1b[?2004h\rsuccess\x1b[0K\r\n\x1b[0K\x1b[D\x1b[2K\r\x1b[?2004l\x1b[?25h\x1b[?1002l\x1b[?1003l\x1b[?1006l",
},
}

Expand Down
122 changes: 51 additions & 71 deletions standard_renderer.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -161,14 +161,20 @@ func (r *standardRenderer) flush() {
defer r.mtx.Unlock()

if r.buf.Len() == 0 || r.buf.String() == r.lastRender {
// Nothing to do
// Nothing to do.
return
}

// Output buffer
// Output buffer.
buf := &bytes.Buffer{}

// Moving to the beginning of the section, that we rendered.
if r.linesRendered > 0 {
buf.WriteString(ansi.CursorUp(r.linesRendered - 1))
}

newLines := strings.Split(r.buf.String(), "\n")
oldLines := strings.Split(r.lastRender, "\n")

// If we know the output's height, we can use it to determine how many
// lines we can render. We drop lines from the top of the render buffer if
Expand All @@ -179,95 +185,69 @@ func (r *standardRenderer) flush() {
}

numLinesThisFlush := len(newLines)
oldLines := strings.Split(r.lastRender, "\n")
skipLines := make(map[int]struct{})
flushQueuedMessages := len(r.queuedMessageLines) > 0 && !r.altScreenActive

// Clear any lines we painted in the last render.
if r.linesRendered > 0 {
for i := r.linesRendered - 1; i > 0; i-- {
// if we are clearing queued messages, we want to clear all lines, since
// printing messages allows for native terminal word-wrap, we
// don't have control over the queued lines
if flushQueuedMessages {
buf.WriteString(ansi.EraseEntireLine)
} else if (len(newLines) <= len(oldLines)) && (len(newLines) > i && len(oldLines) > i) && (newLines[i] == oldLines[i]) {
// If the number of lines we want to render hasn't increased and
// new line is the same as the old line we can skip rendering for
// this line as a performance optimization.
skipLines[i] = struct{}{}
} else if _, exists := r.ignoreLines[i]; !exists {
buf.WriteString(ansi.EraseEntireLine)
}

buf.WriteString(ansi.CursorUp1)
}

if _, exists := r.ignoreLines[0]; !exists {
// We need to return to the start of the line here to properly
// erase it. Going back the entire width of the terminal will
// usually be farther than we need to go, but terminal emulators
// will stop the cursor at the start of the line as a rule.
//
// We use this sequence in particular because it's part of the ANSI
// standard (whereas others are proprietary to, say, VT100/VT52).
// If cursor previous line (ESC[ + <n> + F) were better supported
// we could use that above to eliminate this step.
buf.WriteString(ansi.CursorLeft(r.width))
buf.WriteString(ansi.EraseEntireLine)
}
}

// Merge the set of lines we're skipping as a rendering optimization with
// the set of lines we've explicitly asked the renderer to ignore.
for k, v := range r.ignoreLines {
skipLines[k] = v
}

if flushQueuedMessages {
// Dump the lines we've queued up for printing
// Dump the lines we've queued up for printing.
for _, line := range r.queuedMessageLines {

// Removing previousy rendered content at the end of line.
line = line + ansi.EraseLineRight

_, _ = buf.WriteString(line)
_, _ = buf.WriteString("\r\n")
}
// clear the queued message lines
// Clear the queued message lines.
r.queuedMessageLines = []string{}
}

// Paint new lines
// Paint new lines.
for i := 0; i < len(newLines); i++ {
if _, skip := skipLines[i]; skip {
canSkip := !flushQueuedMessages && // Queuing messages triggers repaint -> we don't have access to previous frame content.
len(oldLines) > i && oldLines[i] == newLines[i] // Previously rendered line is the same.

if _, ignore := r.ignoreLines[i]; ignore || canSkip {
// Unless this is the last line, move the cursor down.
if i < len(newLines)-1 {
buf.WriteString(ansi.CursorDown1)
}
} else {
if i == 0 && r.lastRender == "" {
// On first render, reset the cursor to the start of the line
// before writing anything.
buf.WriteByte('\r')
}
continue
}

line := newLines[i]

// Truncate lines wider than the width of the window to avoid
// wrapping, which will mess up rendering. If we don't have the
// width of the window this will be ignored.
//
// Note that on Windows we only get the width of the window on
// program initialization, so after a resize this won't perform
// correctly (signal SIGWINCH is not supported on Windows).
if r.width > 0 {
line = ansi.Truncate(line, r.width, "")
}
if i == 0 && r.lastRender == "" {
// On first render, reset the cursor to the start of the line
// before writing anything.
buf.WriteByte('\r')
}

_, _ = buf.WriteString(line)
line := newLines[i]

if i < len(newLines)-1 {
_, _ = buf.WriteString("\r\n")
}
// Removing previousy rendered content at the end of line.
line = line + ansi.EraseLineRight

// Truncate lines wider than the width of the window to avoid
// wrapping, which will mess up rendering. If we don't have the
// width of the window this will be ignored.
//
// Note that on Windows we only get the width of the window on
// program initialization, so after a resize this won't perform
// correctly (signal SIGWINCH is not supported on Windows).
if r.width > 0 {
line = ansi.Truncate(line, r.width, "")
}

_, _ = buf.WriteString(line)

if i < len(newLines)-1 {
_, _ = buf.WriteString("\r\n")
}
}

// Clearing left over content from last render.
if r.linesRendered > numLinesThisFlush {
buf.WriteString(ansi.EraseDisplayBelow)
}

r.linesRendered = numLinesThisFlush

// Make sure the cursor is at the start of the last line to keep rendering
Expand Down
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