Skybox image: fix HDR sky binding; clip checkbox/arrow drawing

The HDR sky materials use the "sky" shader with $hdrcompressedtexture (DXT5).
Assigning an RGBA8 procedural texture there sampled as compressed data and
rendered black. Point $hdrbasetexture at the image, undefine
$hdrcompressedtexture (and its 0/1/2 variants) so the shader falls back, and
call IMaterial::Refresh (37) because the sky shader binds textures in
SHADER_INIT, which is otherwise cached.

GUI: draw_checkbox and the card expand chevron ignored the content clip, so
cards scrolled out of view leaked header widgets outside the window.

Log the first regenerator call (size/pitch/first pixel) for diagnosis.

3 files changed, 65 insertions, 23 deletions

diff --git a/CONTEXT.md b/CONTEXT.md
index 5bd0436..b07e407 100644
--- a/CONTEXT.md
+++ b/CONTEXT.md
@@ -144,6 +144,10 @@ vocabulary / decisions.
   `x`, `y`, `category` and an `expanded` bitmask (card index order). Every
   feature now persists an `active` and `bind` pair, including movement, melee
   and spread.
+- All card contents are clipped to the scrolling content rect, including
+  checkboxes and the expand chevron; only clipped fills/text were handled
+  before, so cards scrolled out of view leaked header widgets outside the
+  window.
 - **Colour control (`CK_COLOR`)**: row shows a live swatch; clicking the row
   expands an inline picker (saturation/value square + hue bar + hex/RGB
   preview) instead of three RGB sliders, growing the card in place so it
@@ -377,9 +381,15 @@ vocabulary / decisions.
   `IVTFTexture::ImageData(frame,face,mip)` (39). `IVTFTexture`'s virtual
   destructor occupies two slots, so Width=15, Height=16, RowSizeInBytes=19.
 - The texture is assigned with `IMaterialVar::SetTextureValue` to
-  `$basetexture`, plus `$hdrbasetexture` / `$hdrcompressedtexture` when those
-  vars exist, on every material in the `SkyBox textures` group or named
-  `skybox/*`. The same image is mapped onto all six faces.
+  `$basetexture` and `$hdrbasetexture` on every material in the `SkyBox
+  textures` group or named `skybox/*`. The same image maps onto all six faces.
+- HDR sky materials use the `sky` shader, whose texture binding happens in
+  `SHADER_INIT`: it samples `$hdrcompressedtexture` (DXT5) when defined and
+  otherwise `$hdrbasetexture`. Putting an RGBA8 texture into the DXT5 slot
+  renders black, so `$hdrcompressedtexture` (+ its `0/1/2` variants) is
+  `SetUndefined()` and `$hdrbasetexture` is pointed at our texture instead.
+  The shader state is then rebuilt with `IMaterial::Refresh()` (slot 37),
+  otherwise the old bindings stay cached.
 - Original textures are recorded per material/var (texture pointer plus the
   string as a fallback) and restored when the feature is disabled. Records
   survive level changes so a reused sky material can still be restored; the
diff --git a/src/gui.cpp b/src/gui.cpp
index eb53dff..ebc1f62 100644
--- a/src/gui.cpp
+++ b/src/gui.cpp
@@ -1672,10 +1672,11 @@ void gui_handle_input() {
 // Draw
 // ---------------------------------------------------------------------------
 
-static void draw_checkbox(int x, int y, bool on) {
+static void draw_checkbox(int x, int y, bool on,
+                          const Rect *clip = nullptr) {
   Rect box{x, y, S(15.0f), S(15.0f)};
-  fill(box, on ? C_ACCENT : Col{30, 34, 42, 255});
-  outline(box, C_BORDER);
+  fill(box, on ? C_ACCENT : Col{30, 34, 42, 255}, clip);
+  outline(box, C_BORDER, clip);
   if (on) {
     line(x + S(3.0f), y + S(8.0f), x + S(7.0f), y + S(12.0f), C_BG);
     line(x + S(7.0f), y + S(12.0f), x + S(13.0f), y + S(4.0f), C_BG);
@@ -1719,14 +1720,17 @@ static void draw_card(const Rect &clip, int index, int y) {
   Rect head{cr.x, cr.y, cr.w, hh};
   fill(head, C_HEADER, &clip);
 
-  // expand arrow
+  // expand arrow (clipped like the rest of the card; header rows of cards
+  // scrolled out of view must not leak into the window chrome)
   int ax = cr.x + S(10.0f), ay = cr.y + (hh - S(8.0f)) / 2;
-  if (c.expanded) {
-    line(ax, ay, ax + S(4.0f), ay + S(5.0f), C_DIM);
-    line(ax + S(4.0f), ay + S(5.0f), ax + S(8.0f), ay, C_DIM);
-  } else {
-    line(ax, ay, ax + S(5.0f), ay + S(4.0f), C_DIM);
-    line(ax + S(5.0f), ay + S(4.0f), ax, ay + S(8.0f), C_DIM);
+  if (ay >= clip.y && ay + S(8.0f) <= clip.y + clip.h) {
+    if (c.expanded) {
+      line(ax, ay, ax + S(4.0f), ay + S(5.0f), C_DIM);
+      line(ax + S(4.0f), ay + S(5.0f), ax + S(8.0f), ay, C_DIM);
+    } else {
+      line(ax, ay, ax + S(5.0f), ay + S(4.0f), C_DIM);
+      line(ax + S(5.0f), ay + S(4.0f), ax, ay + S(8.0f), C_DIM);
+    }
   }
 
   // title (wraps instead of truncating)
@@ -1741,7 +1745,7 @@ static void draw_card(const Rect &clip, int index, int y) {
   if (c.feat) {
     bool active = c.feat->active;
     int active_y = cr.y + (hh - S(18.0f)) / 2;
-    draw_checkbox(cr.x + cr.w - S(170.0f), active_y, active);
+    draw_checkbox(cr.x + cr.w - S(170.0f), active_y, active, &clip);
     text_in(clip, cr.x + cr.w - S(148.0f),
             active_y + (S(18.0f) - g_body_h) / 2, active ? "On" : "Off",
             g_font_body, g_body_h, 0, active ? C_GOOD : C_DIM);
@@ -1798,7 +1802,8 @@ static void draw_card(const Rect &clip, int index, int y) {
                    maxw, C_TEXT, S(2.0f));
       if (ct.kind == CK_TOGGLE) {
         bool on = ctrl_val(ct) != 0;
-        draw_checkbox(cr.x + cr.w - S(31.0f), by + (rh - S(15.0f)) / 2, on);
+        draw_checkbox(cr.x + cr.w - S(31.0f), by + (rh - S(15.0f)) / 2, on,
+                      &clip);
         text_in(clip, cr.x + cr.w - S(58.0f), by + (rh - g_body_h) / 2,
                 on ? "On" : "Off", g_font_body, g_body_h, 0,
                 on ? C_GOOD : C_DIM);
diff --git a/src/world.cpp b/src/world.cpp
index 621e5f7..aaee058 100644
--- a/src/world.cpp
+++ b/src/world.cpp
@@ -587,6 +587,13 @@ public:
       return;
     int pitch = vfunc<PitchFn>(vtf, 19)(vtf, 0);   // RowSizeInBytes(0)
     unsigned char *dst = vfunc<DataFn>(vtf, 39)(vtf, 0, 0, 0); // ImageData
+    static bool logged_regen = false;
+    if (!logged_regen) {
+      logged_regen = true;
+      logf("skybox: regenerator %dx%d pitch=%d dst=%p first=%02x%02x%02x%02x",
+           w, h, pitch, dst, g_sky_pixels[0], g_sky_pixels[1],
+           g_sky_pixels[2], g_sky_pixels[3]);
+    }
     if (!dst || pitch <= 0)
       return;
     int rows = h < g_sky_px_h ? h : g_sky_px_h;
@@ -675,24 +682,44 @@ int apply_sky_texture() {
     using SetTexFn = void (*)(void *, void *);
     auto find_var = vfunc<FindVarFn>(mat, 11); // IMaterial::FindVar
 
-    static const char *vars[] = {"$basetexture", "$hdrbasetexture",
-                                 "$hdrcompressedtexture", nullptr};
-    for (int vi = 0; vars[vi]; vi++) {
+    using GetTexFn = void *(*)(void *);
+    using IsDefFn = bool (*)(void *);
+    using UndefFn = void (*)(void *);
+    static const char *tex_vars[] = {"$basetexture", "$hdrbasetexture",
+                                     nullptr};
+    for (int vi = 0; tex_vars[vi]; vi++) {
       bool found = false;
-      void *var = find_var(mat, vars[vi], &found, false);
+      void *var = find_var(mat, tex_vars[vi], &found, false);
       if (!found || !var)
         continue;
-      using GetTexFn = void *(*)(void *);
       auto vget = vfunc<GetStrFn>(var, 6);      // GetStringValue
       auto vgettex = vfunc<GetTexFn>(var, 0);   // GetTextureValue
       auto vset = vfunc<SetTexFn>(var, 14);     // SetTextureValue
-      const char *orig = vget(var);
-      void *orig_tex = vgettex(var);
-      record_orig(name, vars[vi], orig, orig_tex);
+      record_orig(name, tex_vars[vi], vget(var), vgettex(var));
       vset(var, g_sky_tex);
       if (vi == 0)
         hits++;
     }
+    // The HDR sky shader samples $hdrcompressedtexture (DXT5) when defined,
+    // which cannot hold our RGBA texture. Undefine it so the shader falls back
+    // to $hdrbasetexture, which now points at our image.
+    static const char *undef_vars[] = {
+        "$hdrcompressedtexture", "$hdrcompressedtexture0",
+        "$hdrcompressedtexture1", "$hdrcompressedtexture2", nullptr};
+    for (int vi = 0; undef_vars[vi]; vi++) {
+      bool found = false;
+      void *var = find_var(mat, undef_vars[vi], &found, false);
+      if (!found || !var)
+        continue;
+      if (!vfunc<IsDefFn>(var, 17)(var))
+        continue;
+      record_orig(name, undef_vars[vi], vfunc<GetStrFn>(var, 6)(var),
+                  vfunc<GetTexFn>(var, 0)(var));
+      vfunc<UndefFn>(var, 18)(var); // SetUndefined
+    }
+    // The sky shader binds its texture in SHADER_INIT, so changing the vars is
+    // not enough: rebuild the material's shader state.
+    vfunc<void (*)(void *)>(mat, 37)(mat); // IMaterial::Refresh
   }
   return hits;
 }