diff --git a/src/gamelog_internal.h b/src/gamelog_internal.h
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--- /dev/null
+++ b/src/gamelog_internal.h
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+/* $Id$ */
+
+/** @file gamelog_internal.h Declaration shared among gamelog.cpp and saveload/gamelog_sl.cpp */
+
+#ifndef GAMELOG_INTERNAL_H
+#define GAMELOG_INTERNAL_H
+
+#include "network/core/config.h"
+
+/** Type of logged change */
+enum GamelogChangeType {
+	GLCT_MODE,        ///< Scenario editor x Game, different landscape
+	GLCT_REVISION,    ///< Changed game revision string
+	GLCT_OLDVER,      ///< Loaded from savegame without logged data
+	GLCT_PATCH,       ///< Non-networksafe patch value changed
+	GLCT_GRFADD,      ///< Removed GRF
+	GLCT_GRFREM,      ///< Added GRF
+	GLCT_GRFCOMPAT,   ///< Loading compatible GRF
+	GLCT_GRFPARAM,    ///< GRF parameter changed
+	GLCT_GRFMOVE,     ///< GRF order changed
+	GLCT_GRFBUG,      ///< GRF bug triggered
+	GLCT_END,         ///< So we know how many GLCTs are there
+	GLCT_NONE = 0xFF, ///< In savegames, end of list
+};
+
+
+/** Contains information about one logged change */
+struct LoggedChange {
+	GamelogChangeType ct; ///< Type of change logged in this struct
+	union {
+		struct {
+			byte mode;       ///< new game mode - Editor x Game
+			byte landscape;  ///< landscape (temperate, arctic, ...)
+		} mode;
+		struct {
+			char text[NETWORK_REVISION_LENGTH]; ///< revision string, _openttd_revision
+			uint32 newgrf;   ///< _openttd_newgrf_version
+			uint16 slver;    ///< _sl_version
+			byte modified;   ///< _openttd_revision_modified
+		} revision;
+		struct {
+			uint32 type;     ///< type of savegame, @see SavegameType
+			uint32 version;  ///< major and minor version OR ttdp version
+		} oldver;
+		GRFIdentifier grfadd;    ///< ID and md5sum of added GRF
+		struct {
+			uint32 grfid;    ///< ID of removed GRF
+		} grfrem;
+		GRFIdentifier grfcompat; ///< ID and new md5sum of changed GRF
+		struct {
+			uint32 grfid;    ///< ID of GRF with changed parameters
+		} grfparam;
+		struct {
+			uint32 grfid;    ///< ID of moved GRF
+			int32 offset;    ///< offset, positive = move down
+		} grfmove;
+		struct {
+			char *name;      ///< name of the patch
+			int32 oldval;    ///< old value
+			int32 newval;    ///< new value
+		} patch;
+		struct {
+			uint64 data;     ///< additional data
+			uint32 grfid;    ///< ID of problematic GRF
+			byte bug;        ///< type of bug, @see enum GRFBugs
+		} grfbug;
+	};
+};
+
+
+/** Contains information about one logged action that caused at least one logged change */
+struct LoggedAction {
+	LoggedChange *change; ///< First logged change in this action
+	uint32 changes;       ///< Number of changes in this action
+	GamelogActionType at; ///< Type of action
+	uint16 tick;          ///< Tick when it happened
+};
+
+extern LoggedAction *_gamelog_action;
+extern uint _gamelog_actions;
+
+#endif /* GAMELOG_INTERNAL_H */