From 17597f4681fb7d4e200a021092a351645003f394 Mon Sep 17 00:00:00 2001
From: Brandon Scott <xeons@users.noreply.github.com>
Date: Tue, 1 Oct 2019 20:49:10 -0500
Subject: [PATCH] LibGUI: Fix GDirectoryModel lifetime bug.

Thumbnail generation callbacks were getting called after the class was already being destroyed causing a crash to occur.
---
 Libraries/LibGUI/GDirectoryModel.cpp | 8 +++++++-
 Libraries/LibGUI/GDirectoryModel.h   | 3 ++-
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/Libraries/LibGUI/GDirectoryModel.cpp b/Libraries/LibGUI/GDirectoryModel.cpp
index 21955a03c5..20c80c4c0f 100644
--- a/Libraries/LibGUI/GDirectoryModel.cpp
+++ b/Libraries/LibGUI/GDirectoryModel.cpp
@@ -126,14 +126,20 @@ bool GDirectoryModel::fetch_thumbnail_for(const Entry& entry)
     s_thumbnail_cache.set(path, nullptr);
     m_thumbnail_progress_total++;
 
+    auto directory_model = make_weak_ptr();
+
     LibThread::BackgroundAction<RefPtr<GraphicsBitmap>>::create(
         [path] {
             return render_thumbnail(path);
         },
 
-        [this, path](auto thumbnail) {
+        [this, path, directory_model](auto thumbnail) {
             s_thumbnail_cache.set(path, move(thumbnail));
 
+            // class was destroyed, no need to update progress or call any event handlers.
+            if (directory_model.is_null())
+                return;
+
             m_thumbnail_progress++;
             if (on_thumbnail_progress)
                 on_thumbnail_progress(m_thumbnail_progress, m_thumbnail_progress_total);
diff --git a/Libraries/LibGUI/GDirectoryModel.h b/Libraries/LibGUI/GDirectoryModel.h
index 5f7ac03049..3a94e5ff2e 100644
--- a/Libraries/LibGUI/GDirectoryModel.h
+++ b/Libraries/LibGUI/GDirectoryModel.h
@@ -5,7 +5,8 @@
 #include <LibGUI/GModel.h>
 #include <sys/stat.h>
 
-class GDirectoryModel final : public GModel {
+class GDirectoryModel final : public GModel
+    , public Weakable<GDirectoryModel> {
 public:
     static NonnullRefPtr<GDirectoryModel> create() { return adopt(*new GDirectoryModel); }
     virtual ~GDirectoryModel() override;