improve doxygen documentation of PMsgBox.*

src/include/PMsgBox.h

@@ -38,14 +38,67 @@
 #include <TGListBox.h>
 #include <TList.h>
 
+//--------------------------------------------------------------------------
+/**
+ * \brief GUI message box for displaying error messages and warnings.
+ *
+ * PMsgBox is a ROOT-based GUI window that displays multi-line error messages
+ * in a scrollable list box. It provides a simple, modal-like interface for
+ * showing diagnostic information to the user.
+ *
+ * The message box:
+ * - Parses multi-line error messages (separated by newline characters)
+ * - Displays each line in a scrollable list box
+ * - Provides an Exit button that terminates the application
+ * - Uses ROOT's TGMainFrame for window management
+ *
+ * Typical use case:
+ * \code
+ * std::string errorMsg = "Error parsing file:\nLine 42: Invalid syntax\nAborting...";
+ * PMsgBox msgBox(errorMsg, gClient->GetRoot(), 640, 240);
+ * \endcode
+ *
+ * \see TGMainFrame for the base class
+ */
 class PMsgBox : public TGMainFrame {
 
 private:
-   TGListBox *fListBox;
+   TGListBox *fListBox;  ///< List box widget displaying error message lines
 
 public:
+   //-----------------------------------------------------------------------
+   /**
+    * \brief Constructor that creates and displays the message box window.
+    *
+    * Creates a GUI window containing:
+    * - A scrollable list box with the parsed error message
+    * - An Exit button that terminates the application
+    *
+    * The error message is split at newline characters, and each line is
+    * displayed as a separate entry in the list box.
+    *
+    * \param errMsg Multi-line error message string (lines separated by '\n')
+    * \param p Parent window (typically gClient->GetRoot())
+    * \param w Window width in pixels
+    * \param h Window height in pixels
+    */
    PMsgBox(const std::string errMsg, const TGWindow *p, UInt_t w, UInt_t h);
+
+   //-----------------------------------------------------------------------
+   /**
+    * \brief Destructor that cleans up the message box resources.
+    */
    ~PMsgBox() override;
+
+   //-----------------------------------------------------------------------
+   /**
+    * \brief Exit button callback that terminates the application.
+    *
+    * This method is called when the user clicks the Exit button.
+    * It terminates the entire application with exit code 0.
+    *
+    * \note This will exit the entire application, not just close the window
+    */
    void DoExit();
 
    ClassDefOverride(PMsgBox, 0)