From ad4cf7db4cd61d01f1e2191d1d69edd5916d6e88 Mon Sep 17 00:00:00 2001
From: Jan Sucan <jan@jansucan.com>
Date: Sun, 14 Sep 2025 16:17:03 +0200
Subject: 23_a_1: Add solution

---
 ch23/23_a_1/23_a_1.txt    |  1 +
 ch23/23_a_1/PodMainGUI.hs | 47 +++++++++++++++++++++++++++++------------------
 2 files changed, 30 insertions(+), 18 deletions(-)
 create mode 100644 ch23/23_a_1/23_a_1.txt

(limited to 'ch23/23_a_1')

diff --git a/ch23/23_a_1/23_a_1.txt b/ch23/23_a_1/23_a_1.txt
new file mode 100644
index 0000000..7b594a0
--- /dev/null
+++ b/ch23/23_a_1/23_a_1.txt
@@ -0,0 +1 @@
+Present a helpful GUI error message if the call to xmlNew returns Nothing.
diff --git a/ch23/23_a_1/PodMainGUI.hs b/ch23/23_a_1/PodMainGUI.hs
index e557d8b..6c7190d 100644
--- a/ch23/23_a_1/PodMainGUI.hs
+++ b/ch23/23_a_1/PodMainGUI.hs
@@ -47,28 +47,39 @@ main gladepath = withSocketsDo $ handleSqlError $
        timeoutAddFull (yield >> return True)
                       priorityDefaultIdle 100
 
-       -- Load the GUI from the Glade file
-       gui <- loadGlade gladepath
-
-       -- Connect to the database
-       dbh <- connect "pod.db"
-
-       -- Set up our events 
-       connectGui gui dbh
-
-       -- Run the GTK+ main loop; exits after GUI is done
-       mainGUI
+       -- Load XML from glade path
+       xmlGlade <- xmlNew gladepath
+       case xmlGlade of
+         Nothing -> do
+           let errorMsg = "Cannot load glade file " ++ gladepath
+           d <- messageDialogNew Nothing -- No parent window
+                                 [] -- No dialog flags
+                                 MessageError
+                                 ButtonsClose
+                                 errorMsg
+           windowSetTitle d "Error"
+           dialogRun d
+           return ()
+         Just xml -> do
+           -- Load the GUI from the Glade file
+           gui <- loadGlade xml
+
+           -- Connect to the database
+           dbh <- connect "pod.db"
+
+           -- Set up our events 
+           connectGui gui dbh
+
+           -- Run the GTK+ main loop; exits after GUI is done
+           mainGUI
        
-       -- Disconnect from the database at the end
-       disconnect dbh
+           -- Disconnect from the database at the end
+           disconnect dbh
 {-- /snippet main --}
 
 {-- snippet loadGlade --}
-loadGlade gladepath =
-    do -- Load XML from glade path.
-       -- Note: crashes with a runtime error on console if fails!
-       Just xml <- xmlNew gladepath
-
+loadGlade xml =
+    do
        -- Load main window
        mw <- xmlGetWidget xml castToWindow "mainWindow"
 
-- 
cgit v1.2.3