Allow to unscale the output window with a Ctrl-Alt-u hotkey

Signed-off-by: malc <av1474@comtv.ru>

qemu-doc.texi

diff --git a/qemu-doc.texi b/qemu-doc.texi
index 68a6842..2f566b6 100644
--- a/qemu-doc.texi
+++ b/qemu-doc.texi
@@ -241,6 +241,9 @@
 @item Ctrl-Alt-f
 Toggle full screen
 
+@item Ctrl-Alt-u
+Restore the screen's un-scaled dimensions
+
 @item Ctrl-Alt-n
 Switch to virtual console 'n'. Standard console mappings are:
 @table @emph

sdl.c

diff --git a/sdl.c b/sdl.c
index 33edfb8..de63c7f 100644
--- a/sdl.c
+++ b/sdl.c
@@ -569,6 +569,12 @@
                         toggle_full_screen(ds);
                         gui_keysym = 1;
                         break;
+                    case 0x16: /* 'u' key on US keyboard */
+                        scaling_active = 0;
+                        sdl_resize(ds);
+                        vga_hw_invalidate();
+                        vga_hw_update();
+                        break;
                     case 0x02 ... 0x0a: /* '1' to '9' keys */
                         /* Reset the modifiers sent to the current console */
                         reset_keys();