refactor(EditorFragment): simplify padding and collapse logic

- Remove unnecessary imports and methods.
- Simplify padding initialization in EditorPadding.
- Refactor collapse logic in EditorFragment.
- Extract common logic into helper functions.

Author: phodal

core/src/main/kotlin/com/intellij/temporary/gui/block/EditorFragment.kt

@@ -12,15 +12,14 @@ import com.intellij.util.ui.JBUI
 import com.intellij.util.ui.components.BorderLayoutPanel
 import java.awt.Color
 import java.awt.Dimension
-import java.awt.Graphics
 import java.awt.Insets
 import java.awt.event.MouseAdapter
 import java.awt.event.MouseEvent
 import javax.swing.Box
 import javax.swing.JComponent
 
 class EditorPadding(private val editor: Editor, pad: Int) :
-    Box.Filler(Dimension(pad, 0), Dimension(pad, 0), Dimension(pad, 32767)) {
+    Box.Filler(Dimension(pad, pad), Dimension(pad, pad), Dimension(pad, pad)) {
     init {
         setOpaque(true)
         editor.caretModel.addCaretListener(object : CaretListener {
@@ -30,76 +29,74 @@ class EditorPadding(private val editor: Editor, pad: Int) :
         })
     }
 
-    override fun getBackground(): Color {
-        return editor.contentComponent.getBackground()
-    }
-
-    override fun paintComponent(g: Graphics) {
-        super.paintComponent(g)
-    }
+    override fun getBackground(): Color = editor.contentComponent.getBackground()
 }
 
 
 class EditorFragment(private val editor: EditorEx, message: CompletableMessage) {
     private val editorLineThreshold = 6
     private val expandCollapseTextLabel: JBLabel = JBLabel(message.getRole().roleName(), 0).apply {
-        setOpaque(true)
+        isOpaque = true
         isVisible = false
     }
 
-    private val content: BorderLayoutPanel
+    private val content: BorderLayoutPanel = createContentPanel()
     private var collapsed = false
 
-    init {
-        content = object : BorderLayoutPanel() {
+    private fun createContentPanel(): BorderLayoutPanel {
+        return object : BorderLayoutPanel() {
             override fun getPreferredSize(): Dimension {
                 val preferredSize = super.getPreferredSize()
-                val lineCount = editor.document.lineCount
-                val shouldCollapse = lineCount > editorLineThreshold
-                if (shouldCollapse && getCollapsed()) {
+                if (editor.document.lineCount > editorLineThreshold && collapsed) {
                     val lineHeight = editor.lineHeight
-                    val insets = editor.scrollPane.getInsets()
-                    val height = lineHeight * editorLineThreshold + insets.height
-
-                    var editorMaxHeight = height + expandCollapseTextLabel.preferredSize.height + getInsets().height
-                    val header = editor.headerComponent
-                    if (header != null) {
-                        editorMaxHeight += header.getPreferredSize().height
-                    }
-
+                    val insets = editor.scrollPane.insets
+                    val editorMaxHeight = calculateMaxHeight(lineHeight, insets)
                     return Dimension(preferredSize.width, editorMaxHeight)
                 }
-
                 return preferredSize
             }
-        }
 
-        content.setBorder(
-            JBUI.Borders.compound(
+            private fun calculateMaxHeight(lineHeight: Int, insets: Insets): Int {
+                val height = lineHeight * editorLineThreshold + insets.height
+                val headerHeight = editor.headerComponent?.preferredSize?.height ?: 0
+                val labelHeight = expandCollapseTextLabel.preferredSize.height
+                return height + headerHeight + labelHeight + insets().height
+            }
+        }.apply {
+            border = JBUI.Borders.compound(
                 JBUI.Borders.empty(10, 0),
                 JBUI.Borders.customLine(JBColor(0xD4E1570, 0x474071))
             )
-        )
-        content.setOpaque(false)
-        content.addToLeft((EditorPadding(editor, 5)))
-        content.addToCenter((editor.component))
-        content.addToRight((EditorPadding(editor, 5)))
-        content.addToBottom((expandCollapseTextLabel))
+            isOpaque = false
+
+            addToLeft(EditorPadding(editor, 5))
+            addToCenter(editor.component)
+            addToRight(EditorPadding(editor, 5))
+            addToBottom(expandCollapseTextLabel)
+        }
+    }
 
+    init {
         expandCollapseTextLabel.addMouseListener(object : MouseAdapter() {
             override fun mouseClicked(e: MouseEvent?) {
-                setCollapsed(!getCollapsed())
+                toggleCollapsedState()
             }
         })
     }
 
     fun getContent(): JComponent = content
 
-    fun getCollapsed(): Boolean = collapsed
+    fun isCollapsed(): Boolean = collapsed
 
     fun setCollapsed(value: Boolean) {
-        collapsed = value
-        updateExpandCollapseLabel()
+        if (collapsed != value) {
+            collapsed = value
+            updateExpandCollapseLabel()
+        }
+    }
+
+    private fun toggleCollapsedState() {
+        setCollapsed(!collapsed)
     }
 
     fun updateExpandCollapseLabel() {