light: fix for -dirt not implying -minlight_dirt, -sunlight_dirt, -sunlight2_dirt

include/light/light.hh

@@ -388,6 +388,7 @@ extern char mapfilename[1024];
 
 lockable_setting_t *FindSetting(std::string name);
 void SetGlobalSetting(std::string name, std::string value, bool cmdline);
+void FixupGlobalSettings(void);
 void GetFileSpace(byte **lightdata, byte **colordata, byte **deluxdata, int size);
 const modelinfo_t *ModelInfoForFace(const bsp2_t *bsp, int facenum);
 const vec_t *GetSurfaceVertexNormal(const bsp2_t *bsp, const bsp2_dface_t *f, const int v);

light/entities.cc

@@ -864,6 +864,8 @@ LoadEntities(const globalconfig_t &cfg, const bsp2_t *bsp)
     for (const auto &epair : WorldEnt()) {
         SetGlobalSetting(epair.first, epair.second, false);
     }
+    /* apply side effects of settings (in particular "dirt") */
+    FixupGlobalSettings();
     
     assert(all_lights.size() == 0);
     if (nolights) {

light/light.cc

@@ -110,6 +110,31 @@ void SetGlobalSetting(std::string name, std::string value, bool cmdline) {
     sd.setSetting(name, value, cmdline);
 }
 
+void FixupGlobalSettings() {
+    static bool once = false;
+    assert(!once);
+    once = true;
+    
+    // NOTE: This is confusing.. Setting "dirt" "1" implies "minlight_dirt" "1"
+    // (and sunlight_dir/sunlight2_dirt as well), unless those variables were
+    // set by the user to "0".
+    //
+    // We can't just default "minlight_dirt" to "1" because that would enable
+    // dirtmapping by default.
+    
+    if (cfg_static.globalDirt.boolValue()) {
+        if (!cfg_static.minlightDirt.isChanged()) {
+            cfg_static.minlightDirt.setBoolValue(true);
+        }
+        if (!cfg_static.sunlight_dirt.isChanged()) {
+            cfg_static.sunlight_dirt.setFloatValue(1);
+        }
+        if (!cfg_static.sunlight2_dirt.isChanged()) {
+            cfg_static.sunlight2_dirt.setFloatValue(1);
+        }
+    }
+}
+
 static void
 PrintOptionsSummary(void)
 {