Decode HDR-encoded colour ASTC textures, not just linear ones (fixes the Focused vista)

Some environments store colour (sRGB) textures as HDR-encoded ASTC — the Focused vista's sky, water and glow. The
LDR decoder fills those with magenta error texels (the vista showed a huge magenta plane). We already re-decode
linear UNORM textures through the HDR profile for the same reason; do it for colour textures too: when the LDR decode
comes back mostly magenta, re-decode through the HDR profile and sRGB-encode the clamped linear colour so the sRGB
view samples it right (alpha stays linear). Verified by rendering the vista before/after. (A few of the vista's
special detail textures are neither plain LDR nor plain HDR colour and still look speckled; left for a follow-up.)

Also: a GUI-subsystem Windows build now sends the tool modes' log (--snapshot, --panorama, --bench) to the file,
since there's no console for them.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/hsl_renderer.cpp

@@ -2110,7 +2110,7 @@ void HslRenderer::startWorkers() {
                 // Linear (UNORM) textures — normals, ORM, masks — may carry HDR-encoded ASTC blocks, which the LDR
                 // profile turns into magenta error texels (a corrupt ORM made the converted Cascadia's floor a
                 // mirror). Decode them with the HDR profile, unclamped, then clamp to 8 bits (HSR Studio decodes
-                // every UNORM ASTC texture through float too). sRGB colour textures keep the LDR path.
+                // every UNORM ASTC texture through float too). Colour (sRGB) textures start on the LDR path.
                 bool decoded = false;
                 if (!job.srgb) {
                     std::vector<uint16_t> half;
@@ -2125,6 +2125,25 @@ void HslRenderer::startWorkers() {
                     }
                 }
                 if (decoded || astc::decodeASTC(job.src->astc.data() + off, static_cast<u32>(lvl), w, h, job.src->bw, job.src->bh, rgba, false, 1)) {
+                    // A colour texture can be HDR-encoded too (the Focused vista's sky, water and glow): the LDR decode
+                    // then fills it with magenta error texels. Spot that (a lot of exact-magenta texels) and re-decode
+                    // through the HDR profile, sRGB-encoding the clamped linear colour so the sRGB view samples it
+                    // right; alpha is linear either way.
+                    if (job.srgb && !decoded && rgba.size() >= static_cast<size_t>(w) * h * 4) {
+                        size_t mag = 0;
+                        for (size_t q = 0; q + 3 < rgba.size(); q += 4)
+                            if (rgba[q] > 250 && rgba[q + 1] < 8 && rgba[q + 2] > 250) ++mag;
+                        std::vector<uint16_t> half;
+                        if (mag * 4 > static_cast<size_t>(w) * h &&      // a quarter or more of the texels are the error colour
+                            astc::decodeASTCHalf(job.src->astc.data() + off, static_cast<u32>(lvl), w, h, job.src->bw, job.src->bh, half) &&
+                            half.size() >= static_cast<size_t>(w) * h * 4) {
+                            auto toSrgb = [](float c) { c = std::clamp(c, 0.0f, 1.0f); return c <= 0.0031308f ? c * 12.92f : 1.055f * std::pow(c, 1.0f / 2.4f) - 0.055f; };
+                            for (size_t q = 0; q < rgba.size(); ++q) {
+                                const float v = fromHalf(half[q]);
+                                rgba[q] = static_cast<u8>(std::lround(((q & 3) == 3 ? std::clamp(v, 0.0f, 1.0f) : toSrgb(v)) * 255.0f));
+                            }
+                        }
+                    }
                     // A texture cooked without mips (a 6000^2 flipbook) arrives full size: brought within the cap here.
                     while (std::max(w, h) > maxDecodedSide() && rgba.size() >= static_cast<size_t>(w) * h * 4) halveRGBA(rgba, w, h);
                     // The image and its filled staging buffer are made here too: the frame only records the copy.

src/main.cpp

@@ -2064,6 +2064,15 @@ int runInstall(bool install) {
 
 int main(int argc, char** argv) {
     homeos::logCrashes();
+#ifdef _WIN32
+    // A GUI-subsystem build (no console window) has nowhere for the tool modes (--snapshot, --panorama, --bench) to
+    // print; send their messages to the log instead. runVr reopens it afresh for the environment itself.
+    if (!homeos::stderrIsTerminal()) {
+        std::error_code ec;
+        fs::create_directories(rootDir() / "logs", ec);
+        homeos::reopenStderr(rootDir() / "logs" / "frame-home.log", "a");
+    }
+#endif
 #ifdef FH_USE_VOLK
     if (volkInitialize() != VK_SUCCESS) { std::fprintf(stderr, "frame-home: no Vulkan on this system\n"); return 1; }
 #endif