(svn r8106) -Feature/Fix: Add the ability to load savegames when you don't have the exact GRF files in your list. GRF files that are found based on GRFID (but not on matching md5sum) are used instead of disabling them. This does not affect MP games, there you still need an exact match.

-GRF Window colour-codes changed a bit: Static is now grey, and compatible GRF (found locally only based on GRFID) are shown in orange. Compatible GRF's also have an orange status/warning text saying they're not the original the game was saved with.
-Loaded games with something amiss regarding GRF's will show an appropiate warning message.

5 files changed, 62 insertions, 25 deletions

diff --git a/src/lang/english.txt b/src/lang/english.txt
index 98234f09a..ca1baa8aa 100644
--- a/src/lang/english.txt
+++ b/src/lang/english.txt
@@ -2915,6 +2915,11 @@ STR_NEWGRF_DUPLICATE_GRFID                                      :{WHITE}Cannot a
 
 STR_NEWGRF_NOT_FOUND                                            :{RED}Matching file not found
 STR_NEWGRF_DISABLED                                             :{RED}Disabled
+STR_NEWGRF_COMPATIBLE_LOADED                                    :{ORANGE}Matching file not found (compatible GRF loaded)
+
+STR_NEWGRF_COMPATIBLE_LOAD_WARNING                              :{WHITE}Compatible GRF(s) loaded for missing files
+STR_NEWGRF_DISABLED_WARNING                                     :{WHITE}Missing GRF file(s) have been disabled
+STR_NEWGRF_NOT_FOUND_WARNING                                    :{WHITE}Missing GRF file(s) to be able to load game
 
 STR_CURRENCY_WINDOW                                             :{WHITE}Custom currency
 STR_CURRENCY_EXCHANGE_RATE                                      :{LTBLUE}Exchange rate: {ORANGE}{CURRENCY} = £ {COMMA}
diff --git a/src/newgrf_config.cpp b/src/newgrf_config.cpp
index 22cccaee6..534509e89 100644
--- a/src/newgrf_config.cpp
+++ b/src/newgrf_config.cpp
@@ -195,24 +195,45 @@ void ResetGRFConfig(bool defaults)
 }
 
 
-/* Check if all GRFs in the GRF Config can be loaded */
-bool IsGoodGRFConfigList(void)
+/** Check if all GRFs in the GRF config from a savegame can be loaded.
+ * @return will return any of the following 3 values:<br>
+ * <ul>
+ * <li> GCF_ACTIVATED: No problems occured, all GRF files were found and loaded
+ * <li> GCF_COMPATIBLE: For one or more GRF's no exact match was found, but a
+ *     compatible GRF with the same grfid was found and used instead
+ * <li> GCF_NOT_FOUND: For one or more GRF's no match was found at all
+ * </ul> */
+GCF_Flags IsGoodGRFConfigList(void)
 {
-	bool res = true;
-	GRFConfig *c;
+	GCF_Flags res = GCF_ACTIVATED;
 
-	for (c = _grfconfig; c != NULL; c = c->next) {
+	for (GRFConfig *c = _grfconfig; c != NULL; c = c->next) {
 		const GRFConfig *f = FindGRFConfig(c->grfid, c->md5sum);
 		if (f == NULL) {
-			char buf[512], *p = buf;
+			char buf[256], *p = buf;
+
+			/* If we have not found the exactly matching GRF try to find one with the
+			 * same grfid, as it most likely is compatible */
+			f = FindGRFConfig(c->grfid);
+			if (f != NULL) {
+				md5sumToString(buf, lastof(buf), c->md5sum);
+				DEBUG(grf, 1, "NewGRF %08X (%s) not found; checksum %s. Compatibility mode on", BSWAP32(c->grfid), c->filename, buf);
+				SETBIT(c->flags, GCF_COMPATIBLE);
+
+				/* Non-found has precedence over compatibility load */
+				if (res != GCF_NOT_FOUND) res = GCF_COMPATIBLE;
+				goto compatible_grf;
+			}
 
-			p += snprintf(p, lastof(buf) - p, "Couldn't find NewGRF %08X (%s) checksum ", BSWAP32(c->grfid), c->filename);
-			md5sumToString(p, lastof(buf), c->md5sum);
-			ShowInfo(buf);
+			/* No compatible grf was found, mark it as disabled */
+			md5sumToString(buf, lastof(buf), c->md5sum);
+			DEBUG(grf, 0, "NewGRF %08X (%s) not found; checksum %s", BSWAP32(c->grfid), c->filename, buf);
 
-			res = false;
+			SETBIT(c->flags, GCF_NOT_FOUND);
+			res = GCF_NOT_FOUND;
 		} else {
-			DEBUG(grf, 1, "Loading GRF %08X from '%s'", BSWAP32(c->grfid), f->filename);
+compatible_grf:
+			DEBUG(grf, 1, "Loading GRF %08X from %s", BSWAP32(f->grfid), f->filename);
 			/* The filename could be the filename as in the savegame. As we need
 			 * to load the GRF here, we need the correct filename, so overwrite that
 			 * in any case and set the name and info when it is not set already.
@@ -221,6 +242,7 @@ bool IsGoodGRFConfigList(void)
 			if (!HASBIT(c->flags, GCF_COPY)) {
 				free(c->filename);
 				c->filename = strdup(f->filename);
+				memcpy(c->md5sum, f->md5sum, sizeof(c->md5sum));
 				if (c->name == NULL) c->name = strdup(f->name);
 				if (c->info == NULL) c->info = strdup(f->info);
 			}
diff --git a/src/newgrf_config.h b/src/newgrf_config.h
index 7cc90d41f..0864a63a2 100644
--- a/src/newgrf_config.h
+++ b/src/newgrf_config.h
@@ -4,15 +4,16 @@
 #define NEWGRF_CONFIG_H
 
 /* GRF config bit flags */
-enum {
-	GCF_DISABLED,
-	GCF_NOT_FOUND,
-	GCF_ACTIVATED,
-	GCF_SYSTEM,
-	GCF_UNSAFE,
-	GCF_STATIC,
+typedef enum {
+	GCF_DISABLED,  ///< GRF file is disabled
+	GCF_NOT_FOUND, ///< GRF file was not found in the local cache
+	GCF_ACTIVATED, ///< GRF file is active
+	GCF_SYSTEM,    ///< GRF file is an openttd-internal system grf
+	GCF_UNSAFE,    ///< GRF file is unsafe for static usage
+	GCF_STATIC,    ///< GRF file is used statically (can be used in any MP game)
+	GCF_COMPATIBLE,///< GRF file does not exactly match the requested GRF (different MD5SUM), but grfid matches)
 	GCF_COPY,      ///< The data is copied from a grf in _all_grfs
-};
+} GCF_Flags;
 
 typedef struct GRFConfig {
 	char *filename;
@@ -48,7 +49,7 @@ void AppendStaticGRFConfigs(GRFConfig **dst);
 void ClearGRFConfig(GRFConfig **config);
 void ClearGRFConfigList(GRFConfig **config);
 void ResetGRFConfig(bool defaults);
-bool IsGoodGRFConfigList(void);
+GCF_Flags IsGoodGRFConfigList(void);
 bool FillGRFDetails(GRFConfig *config, bool is_static);
 char *GRFBuildParamList(char *dst, const GRFConfig *c, const char *last);
 
diff --git a/src/newgrf_gui.cpp b/src/newgrf_gui.cpp
index 8b1203563..126b4b4fb 100644
--- a/src/newgrf_gui.cpp
+++ b/src/newgrf_gui.cpp
@@ -71,8 +71,9 @@ static void ShowNewGRFInfo(const GRFConfig *c, uint x, uint y, uint w, bool show
 	}
 
 	/* Show flags */
-	if (HASBIT(c->flags, GCF_NOT_FOUND)) y += DrawStringMultiLine(x, y, STR_NEWGRF_NOT_FOUND, w);
-	if (HASBIT(c->flags, GCF_DISABLED))  y += DrawStringMultiLine(x, y, STR_NEWGRF_DISABLED, w);
+	if (HASBIT(c->flags, GCF_NOT_FOUND))  y += DrawStringMultiLine(x, y, STR_NEWGRF_NOT_FOUND, w);
+	if (HASBIT(c->flags, GCF_DISABLED))   y += DrawStringMultiLine(x, y, STR_NEWGRF_DISABLED, w);
+	if (HASBIT(c->flags, GCF_COMPATIBLE)) y += DrawStringMultiLine(x, y, STR_NEWGRF_COMPATIBLE_LOADED, w);
 
 	/* Draw GRF info if it exists */
 	if (c->info != NULL && !StrEmpty(c->info)) {
@@ -317,7 +318,9 @@ static void NewGRFWndProc(Window *w, WindowEvent *e)
 					if (HASBIT(c->flags, GCF_NOT_FOUND) || HASBIT(c->flags, GCF_DISABLED)) {
 						pal = PALETTE_TO_RED;
 					} else if (HASBIT(c->flags, GCF_STATIC)) {
-						pal = PALETTE_TO_YELLOW;
+						pal = PALETTE_TO_GREY;
+					} else if (HASBIT(c->flags, GCF_COMPATIBLE)) {
+						pal = PALETTE_TO_ORANGE;
 					} else if (HASBIT(c->flags, GCF_ACTIVATED)) {
 						pal = PALETTE_TO_GREEN;
 					} else {
diff --git a/src/openttd.cpp b/src/openttd.cpp
index b07622bf3..3640b0aee 100644
--- a/src/openttd.cpp
+++ b/src/openttd.cpp
@@ -1188,8 +1188,14 @@ bool AfterLoadGame(void)
 	// convert road side to my format.
 	if (_opt.road_side) _opt.road_side = 1;
 
-	/* Check all NewGRFs are present */
-	if (!IsGoodGRFConfigList()) return false;
+	/* Check if all NewGRFs are present, we are very strict in MP mode */
+	GCF_Flags gcf_res = IsGoodGRFConfigList();
+	if (_networking && gcf_res != GCF_ACTIVATED) return false;
+
+	switch (gcf_res) {
+		case GCF_COMPATIBLE: _switch_mode_errorstr = STR_NEWGRF_COMPATIBLE_LOAD_WARNING; break;
+		case GCF_NOT_FOUND: _switch_mode_errorstr = STR_NEWGRF_DISABLED_WARNING; break;
+	}
 
 	/* Update current year
 	 * must be done before loading sprites as some newgrfs check it */