Gdk::Pixmap is giving me a segmentation fault on create() - c++

Question

I am doing pixel drawing onto a Gtk::DrawingArea. Sometimes an expose event occurs and I need to redraw everything. But drawing every pixel again is slow, so I'm trying to create a Sdk::Pixmap and draw to it, then draw it to the screen when needed.
I'm trying to create a Sdk::Pixmap and draw to it with draw_point(). Here is my code:
In the hpp:
Glib::RefPtr<Gdk::Pixmap>pixmap;
Glib::RefPtr<Gdk::GC>pixGC;
In the cpp:
Glib::RefPtr<Gdk::Drawable> d = Gdk::Drawable::create(); // this has a value of 1
pixmap = Gdk::Pixmap::create(d, width, height, 3); // this call is giving me a seg fault
pixGC = Gdk::GC::create();
And when drawing:
pixmap->draw_point(pixGC,x, y); // don't even know if this works yet because of the seg fault
What's wrong with my code? :(
Also, I haven't written the code to draw to the actual DrawingArea yet.
Edit: Ok I fixed the first seg fault with:
pixmap = Gdk::Pixmap::create(get_window(), width, height, 3);
pixGC = Gdk::GC::create(get_window());
Thanks to this link:
http://marc.info/?l=gtkmm&m=108547746915009
But now I get this:
The program 'programName' received an X Window System error.
This probably reflects a bug in the program.
The error was 'BadDrawable (invalid Pixmap or Window parameter)'.
(Details: serial 69525 error_code 9 request_code 64 minor_code 0)
(Note to programmers: normally, X errors are reported asynchronously;
that is, you will receive the error a while after causing it.
To debug your program, run it with the --sync command line
option to change this behavior. You can then get a meaningful
backtrace from your debugger if you break on the gdk_x_error() function.)
Stack trace:
Breakpoint 3, 0x00007ffff72830e0 in _XError ()
from /usr/lib/x86_64-linux-gnu/libX11.so.6
(gdb) bt
#0 0x00007ffff72830e0 in _XError () from /usr/lib/x86_64-linux-gnu/libX11.so.6
#1 0x00007ffff72801d1 in ?? () from /usr/lib/x86_64-linux-gnu/libX11.so.6
#2 0x00007ffff7280215 in ?? () from /usr/lib/x86_64-linux-gnu/libX11.so.6
#3 0x00007ffff7281050 in _XReply () from /usr/lib/x86_64-linux-gnu/libX11.so.6
#4 0x00007ffff727c99d in XSync () from /usr/lib/x86_64-linux-gnu/libX11.so.6
#5 0x00007ffff727ca2b in ?? () from /usr/lib/x86_64-linux-gnu/libX11.so.6
#6 0x00007ffff725f954 in XCreatePixmap ()
from /usr/lib/x86_64-linux-gnu/libX11.so.6
#7 0x00007ffff3e2f48d in ?? ()
from /usr/lib/x86_64-linux-gnu/libgdk-x11-2.0.so.0
#8 0x00007ffff6de048d in Gdk::Pixmap::Pixmap (this=0x7fffd4000930,
drawable=..., width=256, height=256, depth=3, __in_chrg=<optimized out>,
__vtt_parm=<optimized out>) at pixmap.cc:55
#9 0x00007ffff6de0d71 in Gdk::Pixmap::create (drawable=..., width=256,
height=256, depth=<optimized out>) at pixmap.cc:317
#10 0x00000000004408e1 in Viewer::start (this=0x7fffffffea00, width=256,
height=256) at viewer.cpp:23
#11 0x000000000042e380 in AppWindow::rayTraceDrawer (this=0x7fffffffe8e0)
at appwindow.cpp:25
#12 0x0000000000432cd8 in std::_Mem_fn<void (AppWindow::*)()>::operator() (
this=0x767b58, __object=0x7fffffffe8e0)
at /usr/include/c++/4.6/functional:551
#13 0x0000000000432b8b in std::_Bind_result<void, std::_Mem_fn<void (AppWindow::---Type <return> to continue, or q <return> to quit---
*)()> (AppWindow*)>::__call<void, , 0>(std::tuple<>&&, std::_Index_tuple<0>, std::_Bind_result<void, std::_Mem_fn<void (AppWindow::*)()> (AppWindow*)>::__enable_if_void<void>::type) (this=0x767b58, __args=...)
at /usr/include/c++/4.6/functional:1287
#14 0x0000000000432ae3 in std::_Bind_result<void, std::_Mem_fn<void (AppWindow::*)()> (AppWindow*)>::operator()<>() (this=0x767b58)
at /usr/include/c++/4.6/functional:1378
#15 0x0000000000432972 in std::thread::_Impl<std::_Bind_result<void, std::_Mem_fn<void (AppWindow::*)()> (AppWindow*)> >::_M_run() (this=0x767b40)
at /usr/include/c++/4.6/thread:117
#16 0x00007ffff6031c78 in ?? () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#17 0x00007ffff589de9a in start_thread ()
from /lib/x86_64-linux-gnu/libpthread.so.0
#18 0x00007ffff55ca3fd in clone () from /lib/x86_64-linux-gnu/libc.so.6
#19 0x0000000000000000 in ?? ()
Is this because I'm creating the pixmap on a background thread?
Edit 2:
Nope, moved to UI thread and still crashing...
Edit 3:
Looks like I may have fixed it. The problem was accessing get_window() too early. Moved code to on_realize and it stopped crashing. Not sure if pixmap is valid yet though...will post after I figure out how to draw from pixmap to drawingarea.

Answer 1

And the solution after so many hours is:
In on_realize of your DrawingArea:
pixmap = Gdk::Pixmap::create(get_window(), width, height, get_window()->get_depth());
pixGC = Gdk::GC::create(get_window());
Draw to pixmap:
pixGC->set_foreground(color);
pixmap->draw_point(pixGC,x,y);
Then to draw to DrawingArea:
get_window()->draw_drawable(get_style()->get_fg_gc(get_state()),
pixmap,
0,0,0,0);