From 6d44e9a1c65b8b70db029feb70cfd8f9bab5e5b3 Mon Sep 17 00:00:00 2001
From: Paul Cornett <paulcor@users.noreply.github.com>
Date: Wed, 18 Sep 2019 22:45:47 -0700
Subject: [PATCH] Fix changing mask on bitmap with alpha on GTK2

See #18508
---
 src/gtk/bitmap.cpp | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/src/gtk/bitmap.cpp b/src/gtk/bitmap.cpp
index 609ab479d0..abef7901a8 100644
--- a/src/gtk/bitmap.cpp
+++ b/src/gtk/bitmap.cpp
@@ -960,6 +960,13 @@ void wxBitmap::SetMask( wxMask *mask )
     AllocExclusive();
     delete M_BMPDATA->m_mask;
     M_BMPDATA->m_mask = mask;
+#ifndef __WXGTK3__
+    if (M_BMPDATA->m_pixbufMask)
+    {
+        g_object_unref(M_BMPDATA->m_pixbufMask);
+        M_BMPDATA->m_pixbufMask = NULL;
+    }
+#endif
 }
 
 bool wxBitmap::CopyFromIcon(const wxIcon& icon)