WIP screen: HiDPI Alt+Tab thumbnails

[rbuj]

test: force 600px thumbnail on HiDPI display with scale factor x2

$ gsettings set org.mate.interface window-scaling-factor 1
$ gsettings set org.mate.Marco.general alt-tab-max-columns 1

Storing window in png file: (for testing...)

• Add the following lines before returning the scaled surface on get_window_surface method (src/core/screen.c)

  static cairo_surface_t *
  get_window_surface (MetaWindow *window)
  {
  <cut>
  char *file = g_strdup_printf ("/tmp/SC_TIME%lu.png", g_get_monotonic_time ());
  cairo_surface_write_to_png (scaled, file);
  g_free (file);
  return scaled;
  }

  Checking thumbnail dimension: 600 x 433, then MAX (600, 433) = 600px

  $ file /tmp/SC_TIME6898955720.png
  /tmp/SC_TIME6898955720.png: PNG image data, 600 x 433, 8-bit/color RGBA, non-interlaced