Gtkmm - always same image when taking screenshot - c++

Question

I have a small c++ (c++11) program that screenshots the whole screen and save it in a file when a button is clicked
Here is my code:
#include <iostream>
#include <gtkmm.h>
using namespace Gtk;
class MainWindow : public Window
{
public:
MainWindow(): m_button("Take Screen Shot")
{
add(m_button);
m_button.signal_clicked().connect(std::bind(&MainWindow::on_mouse_clicked, this));
m_button.show();
}
virtual ~MainWindow() {};
protected:
void on_mouse_clicked()
{
auto root = Gdk::Window::get_default_root_window();
int height = root->get_height();
int width = root->get_width();
auto pixels = Gdk::Pixbuf::create(root, 0, 0, width, height);
pixels->save("s.png", "png");
}
Button m_button;
};
int main(int argc, char *argv[])
{
auto app = Gtk::Application::create(argc, argv);
MainWindow mainapp;
return app->run(mainapp);
}
The problem is: i get always the same image! the state of the screen when the app is launched. I want to get always the current state of the screen

Answer 1

Got the same issue, but on few computers only. Don't know, why this happened, but seems to be gtk and/or display driver error (I've got this bug with Intel display driver).
Anywhere, the followin solution works to me, but only with native x11:
Display *dpy = XOpenDisplay(NULL);
Window rootWnd = DefaultRootWindow(dpy);
XWindowAttributes wa;
XGetWindowAttributes(dpy, rootWnd, &wa);
XImage *rootImg = XGetImage(dpy, rootWnd, 0, 0, wa.width, wa.height, AllPlanes, ZPixmap);
const unsigned long mRed = rootImg->red_mask,
mBlue = rootImg->blue_mask,
mGreen = rootImg->green_mask
;
for(int y = 0; y < wa.height; y++)
{
for(int x = 0; x < wa.width; x++)
{
const unsigned long bgrPixel = XGetPixel(rootImg, x, y);
const unsigned char blue = bgrPixel & mBlue,
green = (bgrPixel & mGreen) >> 8,
red = (bgrPixel & mRed) >> 16,
alpha = bgrPixel >> 24
;
const unsigned long rgbPixel = red | (green << 8) | (blue << 16) | (alpha << 24);
XPutPixel(rootImg, x, y, rgbPixel);
}
}
Glib::RefPtr<Gdk::Pixbuf> img = Gdk::Pixbuf::create_from_data(
(guint8 *)rootImg->data,
Gdk::Colorspace::COLORSPACE_RGB,
rootImg->bits_per_pixel == 32,
8,
rootImg->width,
rootImg->height,
rootImg->bytes_per_line
);
img->save("s.png", "png");
XDestroyImage(rootImg);
XCloseDisplay(dpy);
P.S.: Please, do not forget that Xlib works with BGR, but Gdk::Pixbuf with RGB pattern.