Crash when scrolling through PDF with sidebar open on Layer/Layerstack Preview

[nicolae-stroncea]

Affects versions :

• OS: Linux
• Desktop environment: Ubuntu 20.04, Gnome X11
• libtk: libgtk: 3.24.20
• Xournal version: Xournal++ 1.1.0+dev
• Installation method: From source

To Reproduce

1. Open PDF with X++.
2. Open sidebar on Layer preview.
3. Scroll through PDF. Note: It typically crashes within 1-10 seconds of continuous scrolling.
4. X++ crashes.

Random PDF I found online to test on, but I think this problem occurs on any pdf.
Report_Writing_Process_principles_and_styles.pdf

Additional Details

• I've gotten this crash many times in the past but this is the first time I was able to find a reproducible patern for it.
• Don't think it occurs for 1.0.20

[nicolae-stroncea]

Stack trace:

Date: Sat Feb 27 13:21:44 2021
Error: signal 11
[bt]: (0) xournalpp(+0x4311c2) [0x55d6e6d4e1c2]
[bt]: (1) /lib/x86_64-linux-gnu/libc.so.6(+0x46210) [0x7f60d4191210]
[bt]: (2) /lib/x86_64-linux-gnu/libgtk-3.so.0(gtk_widget_queue_draw+0x32) [0x7f60d5288812]
[bt]: (3) xournalpp(+0x2addf3) [0x55d6e6bcadf3]
[bt]: (4) xournalpp(+0x2ae71e) [0x55d6e6bcb71e]
[bt]: (5) xournalpp(_ZNKSt8functionIFvvEEclEv+0x36) [0x55d6e6d58772]
[bt]: (6) xournalpp(+0x43af9d) [0x55d6e6d57f9d]
[bt]: (7) /lib/x86_64-linux-gnu/libgdk-3.so.0(+0x30f4d) [0x7f60d4e19f4d]
[bt]: (8) /lib/x86_64-linux-gnu/libglib-2.0.so.0(g_main_context_dispatch+0x14e) [0x7f60d56f0e6e]
[bt]: (9) /lib/x86_64-linux-gnu/libglib-2.0.so.0(+0x52220) [0x7f60d56f1220]
[bt]: (10) /lib/x86_64-linux-gnu/libglib-2.0.so.0(g_main_context_iteration+0x33) [0x7f60d56f12c3]
[bt]: (11) /lib/x86_64-linux-gnu/libgio-2.0.so.0(g_application_run+0x205) [0x7f60d4b3cfd5]
[bt]: (12) xournalpp(_ZN11XournalMain3runEiPPc+0x5ef) [0x55d6e6bbdb12]
[bt]: (13) xournalpp(main+0x29) [0x55d6e6b7b2d2]
[bt]: (14) /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf3) [0x7f60d41720b3]
[bt]: (15) xournalpp(_start+0x2e) [0x55d6e6b7b1ee]

Try to get a better stracktrace...
[bt] #1 xournalpp(+0x431734) [0x55d6e6d4e734]
??:0
[bt] #2 /lib/x86_64-linux-gnu/libc.so.6(+0x46210) [0x7f60d4191210]
??:0
[bt] #3 /lib/x86_64-linux-gnu/libgtk-3.so.0(gtk_widget_queue_draw+0x32) [0x7f60d5288812]
??:0
[bt] #4 xournalpp(+0x2addf3) [0x55d6e6bcadf3]
??:0
[bt] #5 xournalpp(+0x2ae71e) [0x55d6e6bcb71e]
??:0
[bt] #6 xournalpp(_ZNKSt8functionIFvvEEclEv+0x36) [0x55d6e6d58772]
??:0
[bt] #7 xournalpp(+0x43af9d) [0x55d6e6d57f9d]
??:0
[bt] #8 /lib/x86_64-linux-gnu/libgdk-3.so.0(+0x30f4d) [0x7f60d4e19f4d]
??:0
[bt] #9 /lib/x86_64-linux-gnu/libglib-2.0.so.0(g_main_context_dispatch+0x14e) [0x7f60d56f0e6e]
??:0
[bt] #10 /lib/x86_64-linux-gnu/libglib-2.0.so.0(+0x52220) [0x7f60d56f1220]
??:0
[bt] #11 /lib/x86_64-linux-gnu/libglib-2.0.so.0(g_main_context_iteration+0x33) [0x7f60d56f12c3]
??:0
[bt] #12 /lib/x86_64-linux-gnu/libgio-2.0.so.0(g_application_run+0x205) [0x7f60d4b3cfd5]
??:0
[bt] #13 xournalpp(_ZN11XournalMain3runEiPPc+0x5ef) [0x55d6e6bbdb12]
??:0
[bt] #14 xournalpp(main+0x29) [0x55d6e6b7b2d2]
??:0
[bt] #15 /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf3) [0x7f60d41720b3]
??:0
[bt] #16 xournalpp(_start+0x2e) [0x55d6e6b7b1ee]
??:0

[nicolae-stroncea]

Update: Layerstack preview in the sidebar has the same issue, though Page Preview does not.

[personalizedrefrigerator]

Additional information & backtrace

This is the backtrace I'm getting from GDB:

GDB says that the segfault is happening on the line highlighted below:

This is where we're calling it:

xournalpp/src/control/jobs/PreviewJob.cpp

Lines 43 to 48 in 81982f8

	ref();
	Util::execInUiThread([=]() {
	gtk_widget_queue_draw(this->sidebarPreview->widget);
	// After the UI job is also done, it can be unreferenced

Adding an if (GTK_IS_WIDGET(this->sidebarPreview->widget)) { block that surrounds gtk_widget_queue_draw moves the segfault to the GTK_IS_WIDGET in the if test.

[personalizedrefrigerator]

I'm working on a fix for this!