I wrote up this simple js-ctypes to take a screenshot on Linux/GTK systems based on StackOverflow :: Taking a screenshot with C\GTK. This code can be copied and pasted in scratchpad and run in browser environment and it works fine, we see that console.info('screenshot:', screenshot.toString()); logs a string with address pointing to somewhere:
Cu.import('resource://gre/modules/ctypes.jsm');
var gdk2 = ctypes.open('libgdk-x11-2.0.so.0');
var _void = ctypes.void_t;
var gint = ctypes.int;
var GdkPixbuf = ctypes.StructType('GdkPixbuf');
var GdkDrawable = ctypes.StructType('GdkDrawable');
var GdkColormap = ctypes.StructType('GdkColormap');
var GdkWindow = ctypes.StructType('GdkWindow');
var int = ctypes.int;
// https://developer.gnome.org/gdk3/stable/gdk3-Windows.html#gdk-get-default-root-window
var gdk_get_default_root_window = gdk2.declare('gdk_get_default_root_window', ctypes.default_abi, GdkWindow.ptr);
// https://developer.gnome.org/gdk3/stable/gdk3-Windows.html#gdk-window-get-origin
var gdk_drawable_get_size = gdk2.declare('gdk_drawable_get_size', ctypes.default_abi,
gint, // return
GdkWindow.ptr, // *window
gint.ptr, // *x
gint.ptr // *y
);
// https://developer.gnome.org/gdk3/stable/gdk3-Windows.html#gdk-window-get-origin
var gdk_window_get_origin = gdk2.declare('gdk_window_get_origin', ctypes.default_abi,
gint, // return
GdkWindow.ptr, // *window
gint.ptr, // *x
gint.ptr // *y
);
// https://developer.gnome.org/gdk2/stable/gdk2-Pixbufs.html#gdk-pixbuf-get-from-drawable
var gdk_pixbuf_get_from_drawable = gdk2.declare('gdk_pixbuf_get_from_drawable', ctypes.default_abi,
GdkPixbuf.ptr, // return
GdkPixbuf.ptr, // *dest
GdkDrawable.ptr, // *src
GdkColormap.ptr, // *cmap
int, // src_x
int, // src_y
int, // dest_x
int, // dest_y
int, // width
int // height
);
var rootGdkWin = gdk_get_default_root_window();
console.info('rootGdkWin:', rootGdkWin.toString());
var x_orig = gint();
var y_orig = gint();
var width = gint();
var height = gint();
var rez_gdkDrawGetSiz = gdk_drawable_get_size(rootGdkWin, width.address(), height.address());
console.info('width:', width.value, 'height:', height.value);
var rez_gdkWinGetOrg = gdk_window_get_origin(rootGdkWin, x_orig.address(), y_orig.address());
console.info('x:', x_orig.value, 'y:', y_orig.value);
var rootGdkDrawable = ctypes.cast(rootGdkWin, GdkDrawable.ptr);
var screenshot = gdk_pixbuf_get_from_drawable(null, rootGdkDrawable, null, x_orig.value, y_orig.value, 0, 0, width.value, height.value);
console.info('screenshot:', screenshot.toString());
gdk2.close();
Now my goal is to run this from a ChromeWorker (off of the main thread) but the call to gdk_pixbuf_get_from_drawable causes it to crash. Here is a super simple ChromeWorker with this code: https://github.com/yajd/ChromeWorker/tree/patch-1 you can install it directly from that github repo with AMO :: GitHub Extension Installer.
I posted asking why it’s crashing in GTK tag section of Stackoverflow here: http://stackoverflow.com/questions/30343641/gdk2-and-gdk3-methods-to-get-pixbuff-of-root-window-failing-with-error-message
I posted there the terminal dump too during crash and Ill paste it here too:
[xcb] Unknown sequence number while processing queue [xcb] Most likely this is a multi-threaded client and XInitThreads has not been called [xcb] Aborting, sorry about that. firefox: ../../src/xcb_io.c:274: poll_for_event: Assertion `!xcb_xlib_threads_sequence_lost' failed. firefox: Fatal IO error 11 (Resource temporarily unavailable) on X server :0.
They told me in the comments of that topic that they said probably running in a thread is casuing the issue, and they were right, but I don’t know how to fix this, I thought to try XInitThreads but this is redundant as this is already called when a ChromeWorker is made: https://dxr.mozilla.org/mozilla-central/search?q=XInitThreads&case=true&=mozilla-central&redirect=true
Does anyone have any ideas on how to run this gdk_pixbuf_get_from_drawable from ChromeWorker? I had same issue with GTK3 method of gdk_pixbuf_get_from_window in terminal on crash it threw this:
(firefox:2624): GLib-GObject-WARNING **: cannot register existing type 'GdkWindow'
(firefox:2624): GLib-CRITICAL **: g_once_init_leave: assertion 'result != 0' failed
(firefox:2624): Gdk-CRITICAL **: gdk_pixbuf_get_from_window: assertion 'GDK_IS_WINDOW (src)' failed
Anyone know how to fix?
Thanks very much I’ve been struggling with it for awhile.