Index: trunk/src/board.c
===================================================================
--- trunk/src/board.c	(revision 29045)
+++ trunk/src/board.c	(revision 29046)
@@ -45,6 +45,8 @@
 
 pcb_board_t *PCB;
 
+static const char core_board_cookie[] = "core/board";
+
 void pcb_board_free(pcb_board_t * pcb)
 {
 	int i;
@@ -259,10 +261,10 @@
 	return pcb_true;
 }
 
-void pcb_board_resize(pcb_coord_t Width, pcb_coord_t Height)
+static void pcb_board_resize_(pcb_board_t *pcb, pcb_coord_t Width, pcb_coord_t Height)
 {
-	PCB->hidlib.size_x = Width;
-	PCB->hidlib.size_y = Height;
+	pcb->hidlib.size_x = Width;
+	pcb->hidlib.size_y = Height;
 
 	/* crosshair range is different if pastebuffer-mode
 	 * is enabled
@@ -276,9 +278,58 @@
 	else
 		pcb_crosshair_set_range(0, 0, Width, Height);
 
-	pcb_board_changed(0);
+	if (pcb == PCB)
+		pcb_board_changed(0);
 }
 
+/*** undoable board resize ***/
+
+typedef struct {
+	pcb_board_t *pcb;
+	pcb_coord_t w, h;
+} undo_board_size_t;
+
+static int undo_board_size_swap(void *udata)
+{
+	undo_board_size_t *s = udata;
+	pcb_coord_t oldw = s->pcb->hidlib.size_x, oldh = s->pcb->hidlib.size_y;
+	pcb_board_resize_(s->pcb, s->w, s->h);
+	s->w = oldw;
+	s->h = oldh;
+	return 0;
+}
+
+static void undo_board_size_print(void *udata, char *dst, size_t dst_len)
+{
+	undo_board_size_t *s = udata;
+	pcb_snprintf(dst, dst_len, "board_size: %mmx%mm", s->w, s->h);
+}
+
+static const uundo_oper_t undo_board_size = {
+	core_board_cookie,
+	NULL, /* free */
+	undo_board_size_swap,
+	undo_board_size_swap,
+	undo_board_size_print
+};
+
+void pcb_board_resize(pcb_coord_t width, pcb_coord_t height, int undoable)
+{
+	undo_board_size_t *s;
+
+	if (!undoable) {
+		pcb_board_resize_(PCB, width, height);
+		return;
+	}
+
+	s = pcb_undo_alloc(PCB, &undo_board_size, sizeof(undo_board_size_t));
+	s->pcb = PCB;
+	s->w = width;
+	s->h = height;
+	undo_board_size_swap(s);
+}
+
+
 void pcb_board_remove(pcb_board_t *Ptr)
 {
 	pcb_undo_clear_list(pcb_true);
Index: trunk/src/board.h
===================================================================
--- trunk/src/board.h	(revision 29045)
+++ trunk/src/board.h	(revision 29046)
@@ -136,7 +136,7 @@
 
 /* changes the maximum size of a layout, notifies the GUI
  * and adjusts the cursor confinement box */
-void pcb_board_resize(pcb_coord_t Width, pcb_coord_t Height);
+void pcb_board_resize(pcb_coord_t Width, pcb_coord_t Height, int undoable);
 
 
 /* free the board and remove its undo list */
Index: trunk/src/plug_io.c
===================================================================
--- trunk/src/plug_io.c	(revision 29045)
+++ trunk/src/plug_io.c	(revision 29046)
@@ -547,7 +547,7 @@
 			pcb_crosshair.Y = PCB->hidlib.size_y/2;
 
 			/* update cursor confinement and output area (scrollbars) */
-			pcb_board_resize(PCB->hidlib.size_x, PCB->hidlib.size_y);
+			pcb_board_resize(PCB->hidlib.size_x, PCB->hidlib.size_y, 0);
 		}
 
 		/* have to be called after pcb_board_resize() so vis update is after a board changed update */
@@ -733,7 +733,7 @@
 				res = -1;
 			}
 			else
-				pcb_board_resize(b.X2*1.5, b.Y2*1.5);
+				pcb_board_resize(b.X2*1.5, b.Y2*1.5, 0);
 		}
 	}
 	return res;
Index: trunk/src_plugins/autocrop/autocrop.c
===================================================================
--- trunk/src_plugins/autocrop/autocrop.c	(revision 29045)
+++ trunk/src_plugins/autocrop/autocrop.c	(revision 29046)
@@ -2,9 +2,9 @@
  *                            COPYRIGHT
  *
  *  pcb-rnd, interactive printed circuit board design
- *  Copyright (C) 2016 Tibor 'Igor2' Palinkas
+ *  Copyright (C) 2016,2020 Tibor 'Igor2' Palinkas
  *
- *  This module, debug, was written and is Copyright (C) 2016 by Tibor Palinkas
+ *  This module, debug, was written and is Copyright (C) by Tibor Palinkas
  *  this module is also subject to the GNU GPL as described below
  *
  *  This program is free software; you can redistribute it and/or modify
@@ -60,7 +60,7 @@
 	pcb_draw_inhibit_inc();
 	pcb_data_clip_inhibit_inc(PCB->Data);
 	pcb_data_move(PCB->Data, dx, dy);
-	pcb_board_resize(w, h);
+	pcb_board_resize(w, h, 0);
 	pcb_data_clip_inhibit_dec(PCB->Data, 1);
 	pcb_draw_inhibit_dec();
 
Index: trunk/src_plugins/dialogs/dlg_pref_sizes.c
===================================================================
--- trunk/src_plugins/dialogs/dlg_pref_sizes.c	(revision 29045)
+++ trunk/src_plugins/dialogs/dlg_pref_sizes.c	(revision 29046)
@@ -47,7 +47,7 @@
 
 	ctx->sizes.lock++;
 	if ((PCB->hidlib.size_x != ctx->dlg[ctx->sizes.wwidth].val.crd) || (PCB->hidlib.size_y != ctx->dlg[ctx->sizes.wheight].val.crd))
-		pcb_board_resize(ctx->dlg[ctx->sizes.wwidth].val.crd, ctx->dlg[ctx->sizes.wheight].val.crd);
+		pcb_board_resize(ctx->dlg[ctx->sizes.wwidth].val.crd, ctx->dlg[ctx->sizes.wheight].val.crd, 0);
 	ctx->sizes.lock--;
 }
 
Index: trunk/src_plugins/io_hyp/parser.c
===================================================================
--- trunk/src_plugins/io_hyp/parser.c	(revision 29045)
+++ trunk/src_plugins/io_hyp/parser.c	(revision 29046)
@@ -655,7 +655,7 @@
 
 	/* resize if board too small */
 	if ((width > PCB->hidlib.size_x) || (height > PCB->hidlib.size_y))
-		pcb_board_resize(width, height);
+		pcb_board_resize(width, height, 0);
 
 	return;
 
Index: trunk/src_plugins/propedit/propsel.c
===================================================================
--- trunk/src_plugins/propedit/propsel.c	(revision 29045)
+++ trunk/src_plugins/propedit/propsel.c	(revision 29046)
@@ -378,7 +378,7 @@
 
 static int brd_resize(pcb_coord_t w, pcb_coord_t h)
 {
-	pcb_board_resize(w, h);
+	pcb_board_resize(w, h, 0);
 	return 1;
 }