improve doxygen documentation of PMsgBox.*

src/classes/PMsgBox.cpp

@@ -29,10 +29,42 @@
 
 #include "PMsgBox.h"
 
+//--------------------------------------------------------------------------
+// Constructor
+//--------------------------------------------------------------------------
+/**
+ * \brief Constructor that creates and displays the message box GUI.
+ *
+ * This constructor performs the following steps:
+ * 1. Creates a scrollable list box widget
+ * 2. Parses the error message string by splitting at newline characters
+ * 3. Populates the list box with individual message lines
+ * 4. Creates an Exit button with callback to DoExit()
+ * 5. Configures layout and displays the window
+ *
+ * The message parsing algorithm:
+ * - Adds an initial empty line
+ * - Splits the input string at each '\n' character
+ * - Each substring becomes a separate list box entry
+ * - Handles multi-line messages gracefully
+ *
+ * GUI Layout:
+ * - List box: 600x200 pixels, expandable, with 5-pixel margins
+ * - Button frame: Fixed width (150px), contains Exit button
+ * - Window title: "Error Message"
+ *
+ * \param errMsg Multi-line error message string with '\n' separators
+ * \param p Parent window pointer (typically gClient->GetRoot())
+ * \param w Initial window width in pixels
+ * \param h Initial window height in pixels
+ *
+ * \note The window is automatically mapped (displayed) after construction
+ * \note The list box ID is set to 89 (ROOT widget identifier)
+ */
 PMsgBox::PMsgBox(const std::string errMsg, const TGWindow *p, UInt_t w, UInt_t h) : TGMainFrame(p, w, h)
 {
    fListBox = new TGListBox(this, 89);
-   
+
    // feed list box with errMsg
    size_t start = 0;
    size_t end = errMsg.find("\n");
@@ -45,7 +77,7 @@ PMsgBox::PMsgBox(const std::string errMsg, const TGWindow *p, UInt_t w, UInt_t h
      end = errMsg.find("\n", start);
      fListBox->AddEntry(tok.c_str(), i++);
    }
-   
+
    fListBox->Resize(600, 200);
    AddFrame(fListBox, new TGLayoutHints(kLHintsTop | kLHintsLeft | kLHintsExpandX | kLHintsExpandY, 5, 5, 5, 5));
 
@@ -67,11 +99,45 @@ PMsgBox::PMsgBox(const std::string errMsg, const TGWindow *p, UInt_t w, UInt_t h
    MapWindow();
 }
 
+//--------------------------------------------------------------------------
+// Destructor
+//--------------------------------------------------------------------------
+/**
+ * \brief Destructor that cleans up the message box resources.
+ *
+ * The ROOT framework automatically handles cleanup of GUI components
+ * (list box, buttons, frames) through the TGMainFrame destructor chain,
+ * so no explicit cleanup is required here.
+ *
+ * \note GUI widgets are managed by ROOT and are automatically deleted
+ *       when the main frame is destroyed
+ */
 PMsgBox::~PMsgBox()
 {
-  // nothing to be done here?
+  // nothing to be done here - ROOT handles GUI cleanup automatically
 }
 
+//--------------------------------------------------------------------------
+// DoExit
+//--------------------------------------------------------------------------
+/**
+ * \brief Exit button callback that terminates the application.
+ *
+ * This method is invoked when the user clicks the Exit button.
+ * It terminates the entire ROOT application with exit code 0,
+ * which causes a clean shutdown of the program.
+ *
+ * The method is connected to the Exit button's "Pressed()" signal
+ * in the constructor via ROOT's signal/slot mechanism:
+ * \code
+ * exit->Connect("Pressed()", "PMsgBox", this, "DoExit()");
+ * \endcode
+ *
+ * \note This terminates the entire application, not just the message box window
+ * \note Exit code 0 indicates successful termination
+ *
+ * \see gApplication for ROOT's global application object
+ */
 void PMsgBox::DoExit()
 {
    gApplication->Terminate(0);