Fix issue Minetest crash when custom font path is not exist

We try to use default fallback for both mono and main font when custom font path is not exist. This way, if Minetest is not corrupted, we could avoid crash.

src/fontengine.cpp

@@ -341,32 +341,70 @@ void FontEngine::initFont(unsigned int basesize, FontMode mode)
 				font_path.c_str(), size, true, true, font_shadow,
 				font_shadow_alpha);
 
-		if (font != NULL) {
+		if (font) {
 			m_font_cache[mode][basesize] = font;
 			return;
 		}
 
-		// try fallback font
+		if (font_config_prefix == "mono_") {
-		errorstream << "FontEngine: failed to load: " << font_path << ", trying to fall back "
+			const std::string &mono_font_path = m_settings->getDefault("mono_font_path");
-				"to fallback font" << std::endl;
 
-		font_path = g_settings->get(font_config_prefix + "fallback_font_path");
+			if (font_path != mono_font_path) {
+				// try original mono font
+				errorstream << "FontEngine: failed to load custom mono "
+						"font: " << font_path << ", trying to fall back to "
+						"original mono font" << std::endl;
 
-		font = gui::CGUITTFont::createTTFont(m_env,
+				font = gui::CGUITTFont::createTTFont(m_env,
-			font_path.c_str(), size, true, true, font_shadow,
+					mono_font_path.c_str(), size, true, true,
-			font_shadow_alpha);
+					font_shadow, font_shadow_alpha);
 
-		if (font != NULL) {
+				if (font) {
-			m_font_cache[mode][basesize] = font;
+					m_font_cache[mode][basesize] = font;
-			return;
+					return;
+				}
+			}
+		} else {
+			// try fallback font
+			errorstream << "FontEngine: failed to load: " << font_path <<
+					", trying to fall back to fallback font" << std::endl;
+
+			font_path = g_settings->get(font_config_prefix + "fallback_font_path");
+
+			font = gui::CGUITTFont::createTTFont(m_env,
+				font_path.c_str(), size, true, true, font_shadow,
+				font_shadow_alpha);
+
+			if (font) {
+				m_font_cache[mode][basesize] = font;
+				return;
+			}
+
+			const std::string &fallback_font_path = m_settings->getDefault("fallback_font_path");
+
+			if (font_path != fallback_font_path) {
+				// try original fallback font
+				errorstream << "FontEngine: failed to load custom fallback "
+						"font: " << font_path << ", trying to fall back to "
+						"original fallback font" << std::endl;
+
+				font = gui::CGUITTFont::createTTFont(m_env,
+					fallback_font_path.c_str(), size, true, true,
+					font_shadow, font_shadow_alpha);
+
+				if (font) {
+					m_font_cache[mode][basesize] = font;
+					return;
+				}
+			}
 		}
 
 		// give up
 		errorstream << "FontEngine: failed to load freetype font: "
 				<< font_path << std::endl;
-		errorstream << "minetest can not continue without a valid font. Please correct "
+		errorstream << "minetest can not continue without a valid font. "
-				"the 'font_path' setting or install the font file in the proper "
+				"Please correct the 'font_path' setting or install the font "
-				"location" << std::endl;
+				"file in the proper location" << std::endl;
 		abort();
 	}
 #endif
@@ -468,7 +506,7 @@ void FontEngine::initSimpleFont(unsigned int basesize, FontMode mode)
 		}
 	}
 
-	if (font != NULL) {
+	if (font) {
 		font->grab();
 		m_font_cache[mode][basesize] = font;
 	}

src/settings.cpp

@@ -362,6 +362,18 @@ const SettingsEntry &Settings::getEntry(const std::string &name) const
 }
 
 
+const SettingsEntry &Settings::getEntryDefault(const std::string &name) const
+{
+	MutexAutoLock lock(m_mutex);
+
+	SettingEntries::const_iterator n;
+	if ((n = m_defaults.find(name)) == m_defaults.end()) {
+		throw SettingNotFoundException("Setting [" + name + "] not found.");
+	}
+	return n->second;
+}
+
+
 Settings *Settings::getGroup(const std::string &name) const
 {
 	const SettingsEntry &entry = getEntry(name);
@@ -380,6 +392,15 @@ const std::string &Settings::get(const std::string &name) const
 }
 
 
+const std::string &Settings::getDefault(const std::string &name) const
+{
+	const SettingsEntry &entry = getEntryDefault(name);
+	if (entry.is_group)
+		throw SettingNotFoundException("Setting [" + name + "] is a group.");
+	return entry.value;
+}
+
+
 bool Settings::getBool(const std::string &name) const
 {
 	return is_yes(get(name));
@@ -568,6 +589,17 @@ bool Settings::getEntryNoEx(const std::string &name, SettingsEntry &val) const
 }
 
 
+bool Settings::getEntryDefaultNoEx(const std::string &name, SettingsEntry &val) const
+{
+	try {
+		val = getEntryDefault(name);
+		return true;
+	} catch (SettingNotFoundException &e) {
+		return false;
+	}
+}
+
+
 bool Settings::getGroupNoEx(const std::string &name, Settings *&val) const
 {
 	try {
@@ -590,6 +622,17 @@ bool Settings::getNoEx(const std::string &name, std::string &val) const
 }
 
 
+bool Settings::getDefaultNoEx(const std::string &name, std::string &val) const
+{
+	try {
+		val = getDefault(name);
+		return true;
+	} catch (SettingNotFoundException &e) {
+		return false;
+	}
+}
+
+
 bool Settings::getFlag(const std::string &name) const
 {
 	try {

src/settings.h

@@ -135,8 +135,10 @@ public:
 	 ***********/
 
 	const SettingsEntry &getEntry(const std::string &name) const;
+	const SettingsEntry &getEntryDefault(const std::string &name) const;
 	Settings *getGroup(const std::string &name) const;
 	const std::string &get(const std::string &name) const;
+	const std::string &getDefault(const std::string &name) const;
 	bool getBool(const std::string &name) const;
 	u16 getU16(const std::string &name) const;
 	s16 getS16(const std::string &name) const;
@@ -165,8 +167,10 @@ public:
 	 ***************************************/
 
 	bool getEntryNoEx(const std::string &name, SettingsEntry &val) const;
+	bool getEntryDefaultNoEx(const std::string &name, SettingsEntry &val) const;
 	bool getGroupNoEx(const std::string &name, Settings *&val) const;
 	bool getNoEx(const std::string &name, std::string &val) const;
+	bool getDefaultNoEx(const std::string &name, std::string &val) const;
 	bool getFlag(const std::string &name) const;
 	bool getU16NoEx(const std::string &name, u16 &val) const;
 	bool getS16NoEx(const std::string &name, s16 &val) const;