gui: Use "minimize" window hint on Windows

Resolves the second half of #300.

This adds conditional code to the gtk_window_present () call in gui.c
to prevent it from running if the user requested it stay minimized in the shortcut
or commandline call on Windows.
It also keeps the splashscreen minimized in that case.

app/display/gimpimagewindow.c

@@ -1170,9 +1170,6 @@ gimp_image_window_set_aux_info (GimpSessionManaged *session_managed,
   else if (StartupInfo.wShowWindow == SW_SHOWMINIMIZED   ||
            StartupInfo.wShowWindow == SW_SHOWMINNOACTIVE ||
            StartupInfo.wShowWindow == SW_MINIMIZE)
-    /* XXX Iconification does not seem to work. I see the
-     * window being iconified and immediately re-raised.
-     * I leave this piece of code for later improvement. */
     gtk_window_iconify (GTK_WINDOW (session_managed));
   else
     /* Another show property not relevant to min/max.

app/gui/gui.c

@@ -86,6 +86,12 @@
 #include "splash.h"
 #include "themes.h"
 
+#ifdef G_OS_WIN32
+#include <windef.h>
+#include <winbase.h>
+#include <windows.h>
+#endif
+
 #ifdef GDK_WINDOWING_QUARTZ
 #import <AppKit/AppKit.h>
 
@@ -539,6 +545,11 @@ gui_restore_after_callback (Gimp               *gimp,
   GimpGuiConfig *gui_config = GIMP_GUI_CONFIG (gimp->config);
   GimpUIManager *image_ui_manager;
   GimpDisplay   *display;
+#ifdef G_OS_WIN32
+  STARTUPINFO    StartupInfo;
+
+  GetStartupInfo (&StartupInfo);
+#endif
 
   if (gimp->be_verbose)
     g_print ("INIT: %s\n", G_STRFUNC);
@@ -611,6 +622,14 @@ gui_restore_after_callback (Gimp               *gimp,
 
       toplevel = gtk_widget_get_toplevel (GTK_WIDGET (shell));
 
+#ifdef G_OS_WIN32
+      /* Prevents window from reappearing on start-up if the user
+       * requested it to be minimized via window hints 
+       */
+      if (StartupInfo.wShowWindow != SW_SHOWMINIMIZED   &&
+          StartupInfo.wShowWindow != SW_SHOWMINNOACTIVE &&
+          StartupInfo.wShowWindow != SW_MINIMIZE)
+#endif
       /*  move keyboard focus to the display  */
       gtk_window_present (GTK_WINDOW (toplevel));
     }

app/gui/splash.c

@@ -25,6 +25,12 @@
 #include <gdk/gdkwayland.h>
 #endif
 
+#ifdef G_OS_WIN32
+#include <windef.h>
+#include <winbase.h>
+#include <windows.h>
+#endif
+
 #include "libgimpbase/gimpbase.h"
 #include "libgimpmath/gimpmath.h"
 #include "libgimpcolor/gimpcolor.h"
@@ -121,6 +127,11 @@ splash_create (Gimp         *gimp,
   GdkRectangle        workarea;
   gint                max_width;
   gint                max_height;
+#ifdef G_OS_WIN32
+  STARTUPINFO         StartupInfo;
+
+  GetStartupInfo (&StartupInfo);
+#endif
 
   g_return_if_fail (splash == NULL);
   g_return_if_fail (GDK_IS_MONITOR (monitor));
@@ -251,6 +262,13 @@ splash_create (Gimp         *gimp,
 
   gtk_widget_show (splash->window);
 
+#ifdef G_OS_WIN32
+  if (StartupInfo.wShowWindow == SW_SHOWMINIMIZED   ||
+      StartupInfo.wShowWindow == SW_SHOWMINNOACTIVE ||
+      StartupInfo.wShowWindow == SW_MINIMIZE)
+    gtk_window_iconify (GTK_WINDOW (splash->window));
+#endif
+
   if (FALSE)
     splash->timer = g_timer_new ();
 }