Fix cursor x-position on empty lines with first-line indent

ComposeTextEditor/src/commonMain/kotlin/com/darkrockstudios/texteditor/cursor/CursorExt.kt

@@ -20,7 +20,7 @@ fun TextEditorState.calculateCursorPosition(): CursorMetrics {
 	val safeCharIndex = charIndex.coerceIn(0, textLength)
 
 	val cursorX = layout.getHorizontalPosition(safeCharIndex, usePrimaryDirection = true) +
-			emptyLineBlockIndent()
+			emptyLineIndent()
 	val cursorY = currentWrappedLine.offset.y - scrollState.value
 	val lineHeight = layout.multiParagraph.getLineHeight(virtualLineIndex)
 
@@ -43,16 +43,22 @@ fun TextEditorState.calculateCursorPosition(): CursorMetrics {
  * Compose's `getHorizontalPosition` returns 0 on an empty line because the
  * paragraph style's [androidx.compose.ui.text.style.TextIndent] doesn't apply
  * to a degenerate `[0, 0)` paragraph range. Add the indent manually so the
- * cursor sits at the indented position on an empty bullet/quote line — without
+ * cursor sits at the indented position on an empty indented line — without
  * this it jumps from `x=0` to `x=indent` the moment the user types the first
- * character. Returns 0 if the line isn't an empty line-block.
+ * character. Covers both line-block indents (bullet/quote/list/code) and the
+ * editor-wide [androidx.compose.ui.text.TextStyle.textIndent]. Returns 0 if
+ * the line isn't empty or no first-line indent is in effect.
  */
-private fun TextEditorState.emptyLineBlockIndent(): Float {
+private fun TextEditorState.emptyLineIndent(): Float {
 	if (cursorPosition.char != 0) return 0f
 	val line = textLines.getOrNull(cursorPosition.line) ?: return 0f
 	if (line.text.isNotEmpty()) return 0f
-	val block = detectLineBlock(cursorPosition.line) ?: return 0f
-	val indent = block.paragraphStyle.textIndent?.firstLine ?: return 0f
+	// Block lines carry their own paragraph-style indent; plain lines inherit
+	// the editor-wide textStyle indent (baked in by updateBookKeeping).
+	val block = detectLineBlock(cursorPosition.line)
+	val indent = block?.paragraphStyle?.textIndent?.firstLine
+		?: textStyle.textIndent?.firstLine
+		?: return 0f
 	val d = density ?: return 0f
 	return with(d) { indent.toPx() }
 }

ComposeTextEditor/src/desktopTest/kotlin/texteditor/CursorIndentTest.kt

@@ -0,0 +1,87 @@
+package texteditor
+
+import androidx.compose.ui.geometry.Size
+import androidx.compose.ui.text.TextMeasurer
+import androidx.compose.ui.text.TextStyle
+import androidx.compose.ui.text.font.createFontFamilyResolver
+import androidx.compose.ui.text.style.TextIndent
+import androidx.compose.ui.unit.Density
+import androidx.compose.ui.unit.LayoutDirection
+import androidx.compose.ui.unit.sp
+import com.darkrockstudios.texteditor.cursor.calculateCursorPosition
+import com.darkrockstudios.texteditor.richstyle.BulletList
+import com.darkrockstudios.texteditor.richstyle.applyLineBlock
+import com.darkrockstudios.texteditor.state.TextEditorState
+import kotlinx.coroutines.test.TestScope
+import org.junit.Test
+import kotlin.test.assertEquals
+
+/**
+ * Verifies that the cursor on an empty line sits at the effective first-line
+ * indent position rather than at `x=0`. Without this, the cursor jumps from 0
+ * to the indent the moment the user types the first character — visible
+ * regression as "the cursor snaps right when I start typing".
+ */
+class CursorIndentTest {
+	private val testScope = TestScope()
+	private val density = Density(1f, 1f)
+
+	private fun realTextMeasurer(): TextMeasurer = TextMeasurer(
+		defaultFontFamilyResolver = createFontFamilyResolver(),
+		defaultDensity = density,
+		defaultLayoutDirection = LayoutDirection.Ltr,
+	)
+
+	private fun freshState(): TextEditorState = TextEditorState(
+		scope = testScope,
+		measurer = realTextMeasurer(),
+	).also {
+		it.density = density
+		it.onViewportSizeChange(Size(500f, 200f))
+	}
+
+	@Test
+	fun `cursor on empty line with editor-wide firstLine indent sits at indent`() {
+		val state = freshState()
+		state.textStyle = TextStyle(textIndent = TextIndent(firstLine = 40.sp))
+
+		val metrics = state.calculateCursorPosition()
+
+		// With Density(1f, 1f), 40.sp == 40px.
+		assertEquals(40f, metrics.position.x, 0.5f)
+	}
+
+	@Test
+	fun `cursor on empty line without firstLine indent sits at x=0`() {
+		val state = freshState()
+		// No textIndent applied.
+
+		val metrics = state.calculateCursorPosition()
+
+		assertEquals(0f, metrics.position.x, 0.5f)
+	}
+
+	@Test
+	fun `cursor on empty bullet line sits at bullet indent`() {
+		val state = freshState()
+		state.applyLineBlock(0, BulletList)
+
+		val metrics = state.calculateCursorPosition()
+
+		// BULLET_LIST_PARAGRAPH_STYLE.textIndent.firstLine == 16.sp.
+		assertEquals(16f, metrics.position.x, 0.5f)
+	}
+
+	@Test
+	fun `block-line indent takes precedence over editor-wide indent`() {
+		val state = freshState()
+		state.textStyle = TextStyle(textIndent = TextIndent(firstLine = 40.sp))
+		state.applyLineBlock(0, BulletList)
+
+		val metrics = state.calculateCursorPosition()
+
+		// Block lines carry their own paragraph style; the editor-wide indent
+		// is not layered on top.
+		assertEquals(16f, metrics.position.x, 0.5f)
+	}
+}