World: replace skybox changer with a PNG skybox image

sv_skyname did not take effect at runtime in this build, so the Skybox card now
replaces the skybox materials' textures with <config dir>/skybox.png.

The PNG is decoded through libpng16's simplified API (dlopen'ed, so no new link
dependency) and uploaded with IMaterialSystem::CreateTextureFromBits as an
RGBA8888 texture. IMaterialVar::SetTextureValue assigns it to $basetexture and
the HDR variants for every material in the SkyBox textures group (all six
faces get the same image).

Original textures are recorded per material/var (texture pointer plus string
fallback) and restored when the feature is off. Records survive level changes
so a reused sky material is still restorable; the override is re-applied to a
new map automatically. The card shows the image path and has a Reload image
button; a missing/unreadable PNG raises an error toast.

1 files changed, 14 insertions, 13 deletions

diff --git a/src/menu.cpp b/src/menu.cpp
index dfd973d..92131d4 100644
--- a/src/menu.cpp
+++ b/src/menu.cpp
@@ -59,8 +59,7 @@ bool g_fog_disable = false;
 int g_fog_rgb[3] = {160, 170, 190};
 int g_fog_start = 200;
 int g_fog_end = 3000;
-FeatureState g_skybox{false, 0}; // sv_skyname override
-int g_skybox_choice = 0;         // 0 = map default
+FeatureState g_skybox{false, 0}; // skybox.png image override
 bool g_item_health = true;
 bool g_item_ammo = true;
 bool g_item_armor = true;
@@ -214,8 +213,8 @@ void config_save() {
              "start=%d\nend=%d\nskybox=%d\ndisable=%d\n",
           g_fog.active, g_fog.bind, g_fog_rgb[0], g_fog_rgb[1], g_fog_rgb[2],
           g_fog_start, g_fog_end, (int)g_fog_skybox, (int)g_fog_disable);
-  fprintf(f, "[skybox]\nactive=%d\nbind=%d\nchoice=%d\n", g_skybox.active,
-          g_skybox.bind, g_skybox_choice);
+  fprintf(f, "[skybox]\nactive=%d\nbind=%d\n", g_skybox.active,
+          g_skybox.bind);
   fprintf(f, "[items]\nactive=%d\nbind=%d\nhealth=%d\nammo=%d\n"
              "armor=%d\nweapons=%d\ncrates=%d\ndistance=%d\nmax_dist=%d\n",
           g_item_esp.active, g_item_esp.bind, (int)g_item_health,
@@ -250,7 +249,7 @@ static bool config_load() {
   FeatureState *cur = nullptr;
   bool in_esp = false, in_bhop = false, in_aim = false, in_silent = false,
        in_jumpbug = false, in_spread = false, in_items = false,
-       in_tint = false, in_fog = false, in_skybox = false;
+       in_tint = false, in_fog = false;
   while (fgets(line, sizeof(line), f)) {
     line[strcspn(line, "\r\n")] = 0;
     if (line[0] == '[') {
@@ -293,7 +292,6 @@ static bool config_load() {
       in_items = (cur == &g_item_esp);
       in_tint = (cur == &g_world_tint);
       in_fog = (cur == &g_fog);
-      in_skybox = (cur == &g_skybox);
     } else if (cur) {
       char *eq = strchr(line, '=');
       if (!eq)
@@ -414,12 +412,6 @@ static bool config_load() {
           g_fog_disable = atoi(val) != 0;
         }
       }
-      if (in_skybox && strcmp(key, "choice") == 0) {
-        int v = atoi(val);
-        if (v < 0) v = 0;
-        if (v >= skybox_option_count()) v = 0;
-        g_skybox_choice = v;
-      }
       if (in_esp) {
         if (strcmp(key, "neutral") == 0)
           g_esp_opt[ESP_OPT_SHOW_NEUTRAL] = atoi(val) != 0;
@@ -459,6 +451,16 @@ const char *config_path_cstr() {
   return path.c_str();
 }
 
+const char *config_file_cstr(const char *name) {
+  static std::string path;
+  std::string p = config_path();
+  size_t slash = p.find_last_of('/');
+  std::string dir =
+      slash == std::string::npos ? std::string(".") : p.substr(0, slash);
+  path = dir + "/" + (name ? name : "");
+  return path.c_str();
+}
+
 void config_reset_defaults() {
   g_bhop = {true, 0};
   g_bhop_autostrafe = true;
@@ -489,7 +491,6 @@ void config_reset_defaults() {
   g_fog_start = 200;
   g_fog_end = 3000;
   g_skybox = {false, 0};
-  g_skybox_choice = 0;
   g_item_health = true;
   g_item_ammo = true;
   g_item_armor = true;