Add support for new font handling for checkrefs.py

As the fonts specified in the GUI templates don't exist as files on disk
anymore after 734386ce9f we can't check if they're specified correctly
the same way as before anymore. Instead, this commit adds validation
of font names to the GUI Relax NG schema and adds a check whether all
fonts referenced in default.cfg exist in the proper location.

binaries/data/mods/mod/gui/gui.rng

@@ -87,6 +87,11 @@
       </data>
     </choice>
   </define>
+  <define name="font">
+    <data type="string">
+      <param name="pattern">(mono|sans)-(bold-|italic-)?(stroke-)?[0-9]{1,3}</param>
+    </data>
+  </define>
   <define name="size">
     <list>
       <data type="decimal"/>
@@ -272,7 +277,9 @@
         </attribute>
       </optional>
       <optional>
-        <attribute name="font"/>
+        <attribute name="font">
+          <ref name="font"/>
+        </attribute>
       </optional>
       <optional>
         <attribute name="format_x"/>
@@ -829,7 +836,9 @@
           </attribute>
         </optional>
         <optional>
-          <attribute name="font"/>
+          <attribute name="font">
+            <ref name="font"/>
+          </attribute>
         </optional>
         <optional>
           <attribute name="maxwidth">

source/tools/entity/checkrefs.py

@@ -1,4 +1,5 @@
 #!/usr/bin/env python3
+import configparser
 import re
 import sys
 from argparse import ArgumentParser
@@ -37,7 +38,6 @@ class CheckRefs:
             "styles": [],
             "scrollbars": [],
             "tooltips": [],
-            "fonts": [],
             "colors": [],
         }
         self.deps_gui_items: dict[str, list[tuple[Path, str]]] = {
@@ -46,7 +46,6 @@ class CheckRefs:
             "styles": [],
             "scrollbars": [],
             "tooltips": [],
-            "fonts": [],
             "colors": [],
         }
         # Three or four positive integers below 256 separated by spaces
@@ -57,7 +56,6 @@ class CheckRefs:
         self.supportedMeshesFormats = ("pmd", "dae")
         self.supportedAnimationFormats = ("psa", "dae")
         self.supportedAudioFormats = "ogg"
-        self.supportedFontFormats = "fnt"
         self.mods = []
         self.__init_logger()
         self.inError = False
@@ -145,7 +143,6 @@ class CheckRefs:
         self.add_particles()
         self.add_soundgroups()
         self.add_audio()
-        self.add_fonts()
         self.add_gui_xml()
         self.add_gui_data()
         self.add_civs()
@@ -156,6 +153,7 @@ class CheckRefs:
         self.add_tips()
         self.check_deps()
         self.check_deps_gui_items()
+        self.check_fonts()
         if args.check_unused:
             self.check_unused()
         if args.validate_templates:
@@ -613,14 +611,6 @@ class CheckRefs:
             [fp for (fp, ffp) in self.find_files("audio/", self.supportedAudioFormats)]
         )
 
-    def add_fonts(self):
-        self.logger.info("Loading fonts...")
-        for fp, _ffp in sorted(self.find_files("fonts/", "png")):
-            self.files.append(fp)
-        for fp, _ffp in sorted(self.find_files("fonts/", self.supportedFontFormats)):
-            self.gui_items["fonts"].append(fp.stem)
-            self.deps.append((fp, fp.with_suffix(".png")))
-
     def add_gui_object(self, parent, fp):
         if parent is None:
             return
@@ -635,8 +625,6 @@ class CheckRefs:
         for attr, val in parent.attrib.items():
             if attr == "name":
                 self.gui_items["gui_objects"].append(val)
-            elif attr == "font":
-                self.deps_gui_items["fonts"].append((fp, val))
             elif attr == "textcolor":
                 self.add_gui_color_attrib(val, fp)
             elif "sound" in attr:
@@ -748,8 +736,6 @@ class CheckRefs:
                                     self.add_gui_sprite_attrib(val, fp)
                                 elif attr == "textcolor":
                                     self.add_gui_color_attrib(val, fp)
-                                elif attr == "font":
-                                    self.deps_gui_items["fonts"].append((fp, val))
                         elif obj.tag == "color":
                             if "name" in obj.attrib:
                                 self.gui_items["colors"].append(obj.get("name"))
@@ -984,6 +970,45 @@ class CheckRefs:
 
             self.InError = True
 
+    def check_fonts(self):
+        """Check that fonts referenced in default.cfg exist."""
+        self.logger.info("Looking for missing font files...")
+
+        base_path = Path(__file__).parents[3]
+        default_cfg_path = base_path / "binaries/data/config/default.cfg"
+        font_dir = self.vfs_root / "mod/fonts"
+
+        try:
+            config = configparser.ConfigParser(allow_unnamed_section=True)
+            config.read(default_cfg_path)
+        except TypeError:
+            # fallback for Python <3.13
+            configparser.UNNAMED_SECTION = "<UNNAMED_SECTION>"
+            config = configparser.ConfigParser()
+            content = "[" + configparser.UNNAMED_SECTION + "]\n"
+            with default_cfg_path.open() as f:
+                content += f.read()
+            config.read_string(content)
+
+        referenced_fonts = set()
+        for section in config.sections():
+            if section == configparser.UNNAMED_SECTION or not section.startswith("fonts."):
+                continue
+
+            for key, value in config[section].items():
+                if key.split(".")[-1] in ["regular", "bold", "italic"]:
+                    for font_name in value.split(","):
+                        referenced_fonts.add(font_name.strip('"'))
+
+        for font in referenced_fonts:
+            if not (font_dir / font).is_file():
+                self.logger.error(
+                    "Missing font '%s' referenced by: %s",
+                    font,
+                    default_cfg_path.relative_to(base_path),
+                )
+                self.inError = True
+
     def check_unused(self):
         self.logger.info("Looking for unused files...")
         deps = defaultdict(set)