feat(devti): enhance issue input panel with placeholder functionality

#353

- Add placeholder text to the text area
- Implement focus listener to handle placeholder visibility
- Adjust text color for placeholder and user input- Update getText and setText methods to handle placeholder

Author: phodal

core/src/main/kotlin/cc/unitmesh/devti/shadow/IssueInputPanel.kt

@@ -5,9 +5,13 @@ import cc.unitmesh.devti.gui.chat.message.ChatActionType
 import cc.unitmesh.devti.sketch.AutoSketchMode
 import com.intellij.openapi.project.Project
 import com.intellij.ui.Gray
+import com.intellij.ui.JBColor
 import com.intellij.ui.components.JBScrollPane
 import com.intellij.util.ui.JBUI
+import com.intellij.util.ui.UIUtil
 import java.awt.*
+import java.awt.event.FocusEvent
+import java.awt.event.FocusListener
 import javax.swing.*
 import javax.swing.border.LineBorder
 
@@ -18,75 +22,80 @@ class IssueInputPanel(
     private val onCancel: () -> Unit
 ) : JPanel(BorderLayout()) {
     private val textArea: JTextArea
+    private var isPlaceholderVisible = true
 
     init {
         background = JBUI.CurrentTheme.ToolWindow.background()
+        border = JBUI.Borders.customLine(UIUtil.getBoundsColor(), 1, 0, 1, 0)
 
         val mainPanel = JPanel(BorderLayout(8, 8)).apply {
-            border = BorderFactory.createCompoundBorder(
-                JBUI.Borders.empty(8),
-                BorderFactory.createCompoundBorder(LineBorder(Gray._230, 1, true),
-                    JBUI.Borders.empty(8)
-                )
-            )
             background = JBUI.CurrentTheme.ToolWindow.background()
         }
 
-        val headerLabel = JLabel(title).apply {
-            font = font.deriveFont(font.size + 2f)
-            border = JBUI.Borders.emptyBottom(10)
-        }
-
         textArea = JTextArea().apply {
             lineWrap = true
             wrapStyleWord = true
-            border = null
             font = Font("Arial", Font.PLAIN, 16)
             rows = 10
+            text = title
+            foreground = JBColor.GRAY
+
+            addFocusListener(object : FocusListener {
+                override fun focusGained(e: FocusEvent?) {
+                    if (isPlaceholderVisible) {
+                        text = ""
+                        foreground = UIManager.getColor("TextArea.foreground")
+                        isPlaceholderVisible = false
+                    }
+                }
+
+                override fun focusLost(e: FocusEvent?) {
+                    if (text.isEmpty()) {
+                        text = title
+                        foreground = JBColor.GRAY
+                        isPlaceholderVisible = true
+                    }
+                }
+            })
         }
 
         val scrollPane = JBScrollPane(textArea).apply {
             border = null
-            preferredSize = Dimension(400, 300)
+            preferredSize = Dimension(preferredSize.width, 300)
         }
 
         val controlsPanel = JPanel(BorderLayout(10, 0)).apply {
-            border = JBUI.Borders.emptyTop(10)
             background = JBUI.CurrentTheme.ToolWindow.background()
         }
 
         val buttonsPanel = JPanel().apply {
             layout = FlowLayout(FlowLayout.RIGHT, 8, 0)
+            background = JBUI.CurrentTheme.ToolWindow.background()
             isOpaque = false
         }
 
         val submitButton = JButton("Submit").apply {
             addActionListener {
-                val text = textArea.text
+                val text = if (isPlaceholderVisible) "" else textArea.text
                 if (text.isNotBlank()) {
                     handlingExecute(text)
                     onSubmit(text)
                 }
             }
-
-            preferredSize = Dimension(90, 32)
         }
 
         val cancelButton = JButton("Cancel").apply {
             addActionListener {
                 onCancel()
             }
-
-            preferredSize = Dimension(90, 32)
         }
 
         buttonsPanel.add(submitButton)
-        buttonsPanel.add(Box.createHorizontalStrut(5))
+        buttonsPanel.add(Box.createHorizontalStrut(4))
         buttonsPanel.add(cancelButton)
 
         controlsPanel.add(buttonsPanel, BorderLayout.EAST)
 
-        mainPanel.add(headerLabel, BorderLayout.NORTH)
         mainPanel.add(scrollPane, BorderLayout.CENTER)
         mainPanel.add(controlsPanel, BorderLayout.SOUTH)
 
@@ -100,10 +109,18 @@ class IssueInputPanel(
         }
     }
 
-    fun getText(): String = textArea.text
+    fun getText(): String = if (isPlaceholderVisible) "" else textArea.text
 
     fun setText(text: String) {
-        textArea.text = text
+        if (text.isNotBlank()) {
+            textArea.text = text
+            textArea.foreground = UIManager.getColor("TextArea.foreground")
+            isPlaceholderVisible = false
+        } else {
+            textArea.text = title
+            textArea.foreground = JBColor.GRAY
+            isPlaceholderVisible = true
+        }
     }
 
     fun requestTextAreaFocus() {