No last empty line

CHANGELOG.md

@@ -7,7 +7,7 @@ New:
 - Nothing yet!
 
 Changed:
-- Nothing yet!
+- An empty line is not added at the end of the output.
 
 Fixed:
 - Nothing yet!

mosaic-runtime/src/commonMain/kotlin/com/jakewharton/mosaic/ansi.kt

@@ -1,19 +1,23 @@
+@file:Suppress("NOTHING_TO_INLINE")
+
 package com.jakewharton.mosaic
 
 import com.github.ajalt.mordant.rendering.AnsiLevel as MordantAnsiLevel
 import com.jakewharton.mosaic.ui.AnsiLevel
 import com.jakewharton.mosaic.ui.Color
 import kotlin.math.roundToInt
 
-private const val ESC = "\u001B"
+internal const val ESC = "\u001B"
 internal const val CSI = "$ESC["
 
 internal const val ansiBeginSynchronizedUpdate = "$CSI?2026h"
 internal const val ansiEndSynchronizedUpdate = "$CSI?2026l"
 
+internal const val ansiClearLineAfterCursor = "${CSI}K"
+internal const val ansiMoveCursorToFirstColumn = "${CSI}0G"
+internal const val ansiClearAllAfterCursor = "${CSI}0J"
+
 internal const val ansiReset = "${CSI}0"
-internal const val clearLine = "${CSI}K"
-internal const val cursorUp = "${CSI}F"
 
 internal const val cursorHide = "$CSI?25l"
 internal const val cursorShow = "$CSI?25h"
@@ -32,6 +36,12 @@ internal const val ansiBgColorOffset = 10
 internal const val ansiSelectorColor256 = 5
 internal const val ansiSelectorColorRgb = 2
 
+internal inline fun StringBuilder.ansiMoveCursorUp(lines: Int) {
+	append(CSI)
+	append(lines)
+	append("A")
+}
+
 internal fun MordantAnsiLevel.toMosaicAnsiLevel(): AnsiLevel {
 	return when (this) {
 		MordantAnsiLevel.NONE -> AnsiLevel.NONE

mosaic-runtime/src/commonMain/kotlin/com/jakewharton/mosaic/rendering.kt

@@ -71,7 +71,7 @@ internal class DebugRendering(
 internal class AnsiRendering(
 	private val ansiLevel: AnsiLevel = AnsiLevel.TRUECOLOR,
 ) : Rendering {
-	private val stringBuilder = StringBuilder(100)
+	private val stringBuilder = StringBuilder(128)
 	private val staticSurfaces = mutableObjectListOf<TextSurface>()
 	private var lastHeight = 0
 
@@ -81,51 +81,44 @@ internal class AnsiRendering(
 
 			append(ansiBeginSynchronizedUpdate)
 
-			var staleLines = lastHeight
-			repeat(staleLines) {
-				append(cursorUp)
-			}
-
-			fun appendSurface(canvas: TextSurface) {
-				for (row in 0 until canvas.height) {
-					canvas.appendRowTo(this, row)
-					if (staleLines-- > 0) {
-						// We have previously drawn on this line. Clear the rest to be safe.
-						append(clearLine)
-					}
-					append("\r\n")
-				}
+			// don't need to move cursor up if there was zero or one line
+			if (lastHeight > 1) {
+				ansiMoveCursorUp(lastHeight - 1)
 			}
+			append(ansiMoveCursorToFirstColumn)
 
+			var addLineBreakAtBeginning = false
 			staticSurfaces.let { staticSurfaces ->
 				node.paintStatics(staticSurfaces, ansiLevel)
 				if (staticSurfaces.isNotEmpty()) {
 					staticSurfaces.forEach { staticSurface ->
-						appendSurface(staticSurface)
+						appendSurface(staticSurface, addLineBreakAtBeginning)
+						if (!addLineBreakAtBeginning && staticSurface.height > 0) {
+							addLineBreakAtBeginning = true
+						}
 					}
 					staticSurfaces.clear()
 				}
 			}
 
 			val surface = node.paint(ansiLevel)
-			appendSurface(surface)
-
-			// If the new output contains fewer lines than the last output, clear those old lines.
-			for (i in 0 until staleLines) {
-				if (i > 0) {
-					append("\r\n")
-				}
-				append(clearLine)
-			}
-
-			// Move cursor back up to end of the new output.
-			repeat(staleLines - 1) {
-				append(cursorUp)
+			if (node.height > 0) {
+				appendSurface(surface, addLineBreakAtBeginning)
 			}
+			lastHeight = surface.height
 
+			append(ansiClearAllAfterCursor)
 			append(ansiEndSynchronizedUpdate)
+		}
+	}
 
-			lastHeight = surface.height
+	private fun StringBuilder.appendSurface(canvas: TextSurface, addLineBreakAtBeginning: Boolean) {
+		for (rowIndex in 0 until canvas.height) {
+			if (rowIndex > 0 || (rowIndex == 0 && addLineBreakAtBeginning)) {
+				append("\r\n")
+			}
+			canvas.appendRowTo(this, rowIndex)
+			append(ansiClearLineAfterCursor)
 		}
 	}
 }

mosaic-runtime/src/commonTest/kotlin/com/jakewharton/mosaic/AnsiRenderingTest.kt

@@ -23,9 +23,8 @@ class AnsiRenderingTest {
 		// TODO We should not draw trailing whitespace.
 		assertThat(rendering.render(rootNode).toString()).isEqualTo(
 			"""
-			|Hello$s
-			|World!
-			|
+			|${ansiMoveCursorToFirstColumn}Hello $ansiClearLineAfterCursor
+			|World!$ansiClearLineAfterCursor$ansiClearAllAfterCursor
 			""".trimMargin().wrapWithAnsiSynchronizedUpdate().replaceLineEndingsWithCRLF(),
 		)
 	}
@@ -40,9 +39,8 @@ class AnsiRenderingTest {
 
 		assertThat(rendering.render(firstRootNode).toString()).isEqualTo(
 			"""
-			|Hello$s
-			|World!
-			|
+			|${ansiMoveCursorToFirstColumn}Hello $ansiClearLineAfterCursor
+			|World!$ansiClearLineAfterCursor$ansiClearAllAfterCursor
 			""".trimMargin().wrapWithAnsiSynchronizedUpdate().replaceLineEndingsWithCRLF(),
 		)
 
@@ -57,11 +55,10 @@ class AnsiRenderingTest {
 
 		assertThat(rendering.render(secondRootNode).toString()).isEqualTo(
 			"""
-			|$cursorUp${cursorUp}Hel$clearLine
-			|lo $clearLine
-			|Wor
-			|ld!
-			|
+			|${ansiMoveCursorUp(1)}${ansiMoveCursorToFirstColumn}Hel$ansiClearLineAfterCursor
+			|lo $ansiClearLineAfterCursor
+			|Wor$ansiClearLineAfterCursor
+			|ld!$ansiClearLineAfterCursor$ansiClearAllAfterCursor
 			""".trimMargin().wrapWithAnsiSynchronizedUpdate().replaceLineEndingsWithCRLF(),
 		)
 	}
@@ -78,11 +75,10 @@ class AnsiRenderingTest {
 
 		assertThat(rendering.render(firstRootNode).toString()).isEqualTo(
 			"""
-			|Hel
-			|lo$s
-			|Wor
-			|ld!
-			|
+			|${ansiMoveCursorToFirstColumn}Hel$ansiClearLineAfterCursor
+			|lo $ansiClearLineAfterCursor
+			|Wor$ansiClearLineAfterCursor
+			|ld!$ansiClearLineAfterCursor$ansiClearAllAfterCursor
 			""".trimMargin().wrapWithAnsiSynchronizedUpdate().replaceLineEndingsWithCRLF(),
 		)
 
@@ -95,10 +91,8 @@ class AnsiRenderingTest {
 
 		assertThat(rendering.render(secondRootNode).toString()).isEqualTo(
 			"""
-			|$cursorUp$cursorUp$cursorUp${cursorUp}Hello $clearLine
-			|World!$clearLine
-			|$clearLine
-			|$clearLine$cursorUp
+			|${ansiMoveCursorUp(3)}${ansiMoveCursorToFirstColumn}Hello $ansiClearLineAfterCursor
+			|World!$ansiClearLineAfterCursor$ansiClearAllAfterCursor
 			""".trimMargin().wrapWithAnsiSynchronizedUpdate().replaceLineEndingsWithCRLF(),
 		)
 	}
@@ -113,9 +107,8 @@ class AnsiRenderingTest {
 
 		assertThat(rendering.render(rootNode).toString()).isEqualTo(
 			"""
-			|World!
-			|Hello
-			|
+			|${ansiMoveCursorToFirstColumn}World!$ansiClearLineAfterCursor
+			|Hello$ansiClearLineAfterCursor$ansiClearAllAfterCursor
 			""".trimMargin().wrapWithAnsiSynchronizedUpdate().replaceLineEndingsWithCRLF(),
 		)
 	}
@@ -130,9 +123,8 @@ class AnsiRenderingTest {
 
 		assertThat(rendering.render(firstRootNode).toString()).isEqualTo(
 			"""
-			|One
-			|Two
-			|
+			|${ansiMoveCursorToFirstColumn}One$ansiClearLineAfterCursor
+			|Two$ansiClearLineAfterCursor$ansiClearAllAfterCursor
 			""".trimMargin().wrapWithAnsiSynchronizedUpdate().replaceLineEndingsWithCRLF(),
 		)
 
@@ -145,9 +137,8 @@ class AnsiRenderingTest {
 
 		assertThat(rendering.render(secondRootNode).toString()).isEqualTo(
 			"""
-			|${cursorUp}Three$clearLine
-			|Four
-			|
+			|${ansiMoveCursorToFirstColumn}Three$ansiClearLineAfterCursor
+			|Four$ansiClearLineAfterCursor$ansiClearAllAfterCursor
 			""".trimMargin().wrapWithAnsiSynchronizedUpdate().replaceLineEndingsWithCRLF(),
 		)
 	}
@@ -178,13 +169,12 @@ class AnsiRenderingTest {
 
 		assertThat(rendering.render(rootNode).toString()).isEqualTo(
 			"""
-			|One
-			|Two
-			|Three
-			|Four
-			|Five
-			|Sup
-			|
+			|${ansiMoveCursorToFirstColumn}One$ansiClearLineAfterCursor
+			|Two$ansiClearLineAfterCursor
+			|Three$ansiClearLineAfterCursor
+			|Four$ansiClearLineAfterCursor
+			|Five$ansiClearLineAfterCursor
+			|Sup$ansiClearLineAfterCursor$ansiClearAllAfterCursor
 			""".trimMargin().wrapWithAnsiSynchronizedUpdate().replaceLineEndingsWithCRLF(),
 		)
 	}
@@ -204,10 +194,9 @@ class AnsiRenderingTest {
 
 		assertThat(rendering.render(firstRootNode).toString()).isEqualTo(
 			"""
-			|Static
-			|TopTopTop
-			|LeftLeft$s
-			|
+			|${ansiMoveCursorToFirstColumn}Static$ansiClearLineAfterCursor
+			|TopTopTop$ansiClearLineAfterCursor
+			|LeftLeft $ansiClearLineAfterCursor$ansiClearAllAfterCursor
 			""".trimMargin().wrapWithAnsiSynchronizedUpdate().replaceLineEndingsWithCRLF(),
 		)
 	}

mosaic-runtime/src/commonTest/kotlin/com/jakewharton/mosaic/CounterTest.kt

@@ -33,18 +33,9 @@ class CounterTest {
 	@Test fun counterWithAnsi() = runTest {
 		runMosaicTest(withAnsi = true) {
 			setCounter()
-			assertThat(awaitRenderSnapshot()).isEqualTo(
-				"""
-				|${ansiBeginSynchronizedUpdate}The count is: 0
-				|$ansiEndSynchronizedUpdate
-				""".trimMargin().replaceLineEndingsWithCRLF(),
-			)
-			for (i in 1..20) {
+			for (i in 0..20) {
 				assertThat(awaitRenderSnapshot()).isEqualTo(
-					"""
-					|${ansiBeginSynchronizedUpdate}${cursorUp}The count is: ${i}$clearLine
-					|$ansiEndSynchronizedUpdate
-					""".trimMargin().replaceLineEndingsWithCRLF(),
+					"${ansiMoveCursorToFirstColumn}The count is: ${i}$ansiClearLineAfterCursor$ansiClearAllAfterCursor".wrapWithAnsiSynchronizedUpdate(),
 				)
 			}
 		}

mosaic-runtime/src/commonTest/kotlin/com/jakewharton/mosaic/MosaicTest.kt

@@ -45,10 +45,9 @@ class MosaicTest {
 		}
 		assertThat(actual).isEqualTo(
 			"""
-			|One $s
-			|Two $s
-			|Three
-			|
+			|${ansiMoveCursorToFirstColumn}One  $ansiClearLineAfterCursor
+			|Two  $ansiClearLineAfterCursor
+			|Three$ansiClearLineAfterCursor$ansiClearAllAfterCursor
 			""".trimMargin().wrapWithAnsiSynchronizedUpdate().replaceLineEndingsWithCRLF(),
 		)
 	}
@@ -75,10 +74,9 @@ class MosaicTest {
 		}
 		assertThat(actual).isEqualTo(
 			"""
-			|One $s
-			|Two $s
-			|Three
-			|
+			|${ansiMoveCursorToFirstColumn}One  $ansiClearLineAfterCursor
+			|Two  $ansiClearLineAfterCursor
+			|Three$ansiClearLineAfterCursor$ansiClearAllAfterCursor
 			""".trimMargin().wrapWithAnsiSynchronizedUpdate().replaceLineEndingsWithCRLF(),
 		)
 	}
@@ -105,10 +103,9 @@ class MosaicTest {
 		}
 		assertThat(actual).isEqualTo(
 			"""
-			|One $s
-			|Two $s
-			|Three
-			|
+			|${ansiMoveCursorToFirstColumn}One  $ansiClearLineAfterCursor
+			|Two  $ansiClearLineAfterCursor
+			|Three$ansiClearLineAfterCursor$ansiClearAllAfterCursor
 			""".trimMargin().wrapWithAnsiSynchronizedUpdate().replaceLineEndingsWithCRLF(),
 		)
 	}
@@ -147,10 +144,9 @@ class MosaicTest {
 		}
 		assertThat(actual).isEqualTo(
 			"""
-			|One $s
-			|Two $s
-			|Three
-			|
+			|${ansiMoveCursorToFirstColumn}One  $ansiClearLineAfterCursor
+			|Two  $ansiClearLineAfterCursor
+			|Three$ansiClearLineAfterCursor$ansiClearAllAfterCursor
 			""".trimMargin().wrapWithAnsiSynchronizedUpdate().replaceLineEndingsWithCRLF(),
 		)
 	}
@@ -167,10 +163,9 @@ class MosaicTest {
 		}
 		assertThat(actual).isEqualTo(
 			"""
-			|One $s
-			|Two $s
-			|Three
-			|
+			|${ansiMoveCursorToFirstColumn}One  $ansiClearLineAfterCursor
+			|Two  $ansiClearLineAfterCursor
+			|Three$ansiClearLineAfterCursor$ansiClearAllAfterCursor
 			""".trimMargin().wrapWithAnsiSynchronizedUpdate().replaceLineEndingsWithCRLF(),
 		)
 	}
@@ -191,10 +186,9 @@ class MosaicTest {
 		actuals.forEach { actual ->
 			assertThat(actual).isEqualTo(
 				"""
-				|One $s
-				|Two $s
-				|Three
-				|
+				|${ansiMoveCursorToFirstColumn}One  $ansiClearLineAfterCursor
+				|Two  $ansiClearLineAfterCursor
+				|Three$ansiClearLineAfterCursor$ansiClearAllAfterCursor
 				""".trimMargin().wrapWithAnsiSynchronizedUpdate().replaceLineEndingsWithCRLF(),
 			)
 		}

mosaic-runtime/src/commonTest/kotlin/com/jakewharton/mosaic/TestMosaicComposition.kt

@@ -80,9 +80,10 @@ private class RealTestMosaicComposition(
 		} else {
 			rendering.render(rootNode).toString()
 				.removeSurrounding(ansiBeginSynchronizedUpdate, ansiEndSynchronizedUpdate)
-				.removeSuffix("\r\n") // without last line break for simplicity
-				.replace(clearLine, "")
-				.replace(cursorUp, "")
+				.replace(Regex("$ESC\\[\\d+A"), "")
+				.removePrefix(ansiMoveCursorToFirstColumn)
+				.removeSuffix(ansiClearAllAfterCursor)
+				.replace(ansiClearLineAfterCursor, "")
 				.replace("\r\n", "\n") // CRLF to LF for simplicity
 		}
 		renderSnapshots.trySend(stringRender)