[librptexture] ASTC, GodotSTEX: Fix build with ASTC decoding disabled.

Note that the ASTC container parser is still available even if ASTC
decoding is disabled, since it can at least get metadata, e.g. the
image dimensions.

src/librptexture/fileformat/ASTC.cpp

@@ -98,9 +98,10 @@ rp_image_const_ptr ASTCPrivate::loadImage(void)
 		return img;
 	} else if (!this->isValid || !this->file) {
 		// Can't load the image.
-		return nullptr;
+		return {};
 	}
 
+#ifdef ENABLE_ASTC
 	// NOTE: We can't use astcHeader's width/height fields because
 	// they're 24-bit values. Use dimensions[] instead.
 
@@ -113,17 +114,17 @@ rp_image_const_ptr ASTCPrivate::loadImage(void)
 	    dimensions[1] > 32768)
 	{
 		// Invalid image dimensions.
-		return nullptr;
+		return {};
 	}
 
 	if (dimensions[2] > 1) {
 		// 3D textures are not supported.
-		return nullptr;
+		return {};
 	}
 
 	if (file->size() > 128*1024*1024) {
 		// Sanity check: VTF files shouldn't be more than 128 MB.
-		return nullptr;
+		return {};
 	}
 	const uint32_t file_sz = static_cast<uint32_t>(file->size());
 
@@ -137,7 +138,7 @@ rp_image_const_ptr ASTCPrivate::loadImage(void)
 		astcHeader.blockdimX, astcHeader.blockdimY);
 	if (expected_size == 0 || expected_size > file_sz) {
 		// Invalid image size.
-		return nullptr;
+		return {};
 	}
 
 	// The ASTC file format does not support mipmaps.
@@ -148,7 +149,7 @@ rp_image_const_ptr ASTCPrivate::loadImage(void)
 	int ret = file->seek(texDataStartAddr);
 	if (ret != 0) {
 		// Seek error.
-		return nullptr;
+		return {};
 	}
 
 	// Read the texture data.
@@ -156,7 +157,7 @@ rp_image_const_ptr ASTCPrivate::loadImage(void)
 	size_t size = file->read(buf.get(), expected_size);
 	if (size != expected_size) {
 		// Read error.
-		return nullptr;
+		return {};
 	}
 
 	// Decode the image.
@@ -165,6 +166,10 @@ rp_image_const_ptr ASTCPrivate::loadImage(void)
 		buf.get(), expected_size,
 		astcHeader.blockdimX, astcHeader.blockdimY);
 	return img;
+#else /* !ENABLE_ASTC */
+	// ASTC decoder is disabled.
+	return {};
+#endif /* ENABLE_ASTC */
 }
 
 /** ASTC **/

src/librptexture/fileformat/GodotSTEX.cpp

@@ -842,6 +842,7 @@ rp_image_const_ptr GodotSTEXPrivate::loadImage(int mip)
 				// TODO
 				break;
 
+#ifdef ENABLE_ASTC
 			case STEX4_FORMAT_ASTC_4x4:
 				img = ImageDecoder::fromASTC(
 					mdata.width, mdata.height,
@@ -852,6 +853,7 @@ rp_image_const_ptr GodotSTEXPrivate::loadImage(int mip)
 					mdata.width, mdata.height,
 					buf.get(), mdata.size, 8, 8);
 				break;
+#endif /* ENABLE_ASTC */
 		}
 	} else {
 		assert(!"Unsupported stexVersion value.");