[terminal] correct startOffset in TerminalOutputModelListener.afterContentChanged when update exceeds maxCapacity

GitOrigin-RevId: 4e9b06974f140624d16a2f13f084662d4be09f2f

plugins/terminal/src/org/jetbrains/plugins/terminal/block/reworked/TerminalOutputModelImpl.kt

@@ -13,6 +13,7 @@ import org.jetbrains.plugins.terminal.block.output.TerminalOutputHighlightingsSn
 import org.jetbrains.plugins.terminal.block.output.TextStyleAdapter
 import org.jetbrains.plugins.terminal.block.session.StyleRange
 import org.jetbrains.plugins.terminal.block.ui.BlockTerminalColorPalette
+import kotlin.math.max
 
 /**
  * [maxOutputLength] limits the length of the document. Zero means unlimited length.
@@ -92,7 +93,7 @@ internal class TerminalOutputModelImpl(
 
     val trimmedCount = trimToSize()
 
-    return replaceStartOffset - trimmedCount
+    return max(0, replaceStartOffset - trimmedCount)
   }
 
   /** Returns trimmed characters count */

plugins/terminal/tests/org/jetbrains/plugins/terminal/reworked/TerminalOutputModelTest.kt

@@ -9,6 +9,7 @@ import kotlinx.coroutines.runBlocking
 import org.jetbrains.plugins.terminal.block.output.HighlightingInfo
 import org.jetbrains.plugins.terminal.block.output.TerminalOutputHighlightingsSnapshot
 import org.jetbrains.plugins.terminal.block.output.TextStyleAdapter
+import org.jetbrains.plugins.terminal.block.reworked.TerminalOutputModelListener
 import org.jetbrains.plugins.terminal.block.session.StyleRange
 import org.jetbrains.plugins.terminal.block.ui.BlockTerminalColorPalette
 import org.jetbrains.plugins.terminal.reworked.util.TerminalSessionTestUtil
@@ -140,6 +141,38 @@ internal class TerminalOutputModelTest : BasePlatformTestCase() {
     assertEquals(expectedHighlightingsSnapshot, model.getHighlightings())
   }
 
+  @Test
+  fun `update exceeds maxCapacity`() = runBlocking(Dispatchers.EDT) {
+    val model = TerminalSessionTestUtil.createOutputModel(maxLength = 10)
+    val startOffsets = mutableListOf<Int>()
+    model.addListener(testRootDisposable, object: TerminalOutputModelListener {
+      override fun afterContentChanged(startOffset: Int) {
+        startOffsets.add(startOffset)
+      }
+    })
+
+    model.update(0, """
+      abcdef
+      ghijkl
+    """.trimIndent(), emptyList())
+
+    assertEquals("""
+      def
+      ghijkl
+    """.trimIndent(), model.document.text)
+
+    model.update(1, """
+      mnopqrs
+      tuvwxyz
+    """.trimIndent(), emptyList())
+
+    assertEquals("""
+      rs
+      tuvwxyz
+    """.trimIndent(), model.document.text)
+    assertEquals(listOf(0, 0), startOffsets)
+  }
+
   @Test
   fun `update editor content from the start when some lines were trimmed already (clear)`() = runBlocking(Dispatchers.EDT) {
     val model = TerminalSessionTestUtil.createOutputModel(maxLength = 10)