The bottom face can now be shifted and rotated as well.

- solidify/overlap.h, solidify/overlap.c (edit_top, overlap_edit): select
  the face to rotate and shift
- solidify/overlap.c (scroll_event): select face to manipulate based on
  edit_top
- solidify/solidify.c (a_b, gui_buttons): new button B+A to select the
  bottom face for editing
- solidify/solidify.c clicked): call overlap_edit to select face to edit

solidify/overlap.c

@@ -28,6 +28,7 @@
 
 
 static int has_osd;
+static int edit_top;
 
 
 static int sx(const struct solid *s)
@@ -405,16 +406,20 @@ static gboolean scroll_event(GtkWidget *widget, GdkEventScroll *event,
 	switch (event->direction) {
 	case GDK_SCROLL_UP:
 		if (center)
-			shift(&s->a->m, dx, dy, dist);
+			shift(edit_top ? &s->a->m : &s->b->m,
+			    edit_top ? dx : -dx, dy, dist);
 		else
-			rotate(&s->a->m, dx > 0 ? rot : -rot);
+			rotate(edit_top ? &s->a->m : &s->b->m,
+			    dx > 0 ? rot : -rot);
 		draw_image(darea, s, osd);
 		break;
 	case GDK_SCROLL_DOWN:
 		if (center)
-			shift(&s->a->m, dx, dy, -dist);
+			shift(edit_top ? &s->a->m : &s->b->m,
+			    edit_top ? dx : -dx, dy, -dist);
 		else
-			rotate(&s->a->m, dx > 0 ? -rot : rot);
+			rotate(edit_top ? &s->a->m : &s->b->m,
+			    dx > 0 ? -rot : rot);
 		draw_image(darea, s, osd);
 		break;
 	default:
@@ -446,6 +451,12 @@ static gboolean motion_notify_event(GtkWidget *widget, GdkEventMotion *event,
 }
 
 
+void overlap_edit(int top)
+{
+	edit_top = top;
+}
+
+
 void overlap(GtkWidget *canvas, struct solid *s)
 {
 	GtkWidget *evbox, *darea;

solidify/overlap.h

@@ -18,6 +18,7 @@
 #include "solid.h"
 
 
+void overlap_edit(int top);
 void overlap(GtkWidget *canvas, struct solid *solid);
 
 #endif /* !OVERLAP_H */

solidify/solidify.c

@@ -28,13 +28,16 @@
 
 static struct project *prj;
 static const struct face *active; /* NULL if overlapping */
-static GtkWidget *canvas;
+static GtkWidget *canvas, *a_b;
 
 
 static void clicked(GtkButton *button, gpointer user_data)
 {
 	struct face *face = user_data;
 
+	if (!face)
+		overlap_edit(button == GTK_BUTTON(a_b));
+
 	if (active == face)
 		return;
 
@@ -66,7 +69,12 @@ static GtkWidget *gui_buttons(void)
 	g_signal_connect(G_OBJECT(but), "clicked",
 	    G_CALLBACK(clicked), prj->s.b);
 
-	but = gtk_button_new_with_label("A+B");
+	a_b = gtk_button_new_with_label("A+B");
+	gtk_box_pack_start(GTK_BOX(vbox), a_b, FALSE, FALSE, 0);
+	g_signal_connect(G_OBJECT(a_b), "clicked",
+	    G_CALLBACK(clicked), NULL);
+
+	but = gtk_button_new_with_label("B+A");
 	gtk_box_pack_start(GTK_BOX(vbox), but, FALSE, FALSE, 0);
 	g_signal_connect(G_OBJECT(but), "clicked",
 	    G_CALLBACK(clicked), NULL);