Updated change log for 2.5
@@ -9,16 +9,36 @@ clocked at 4.2 GHz, running astcenc using 6 threads.
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## 2.5
-**Status:** In development
+**Status:** In development, due late March 2021
-The 2.5 release is the sixth release in the 2.x series. For this release
-onwards the 2.x series is aiming to freeze image quality compared to 2.4,
-allowing only minor differences caused by rounding and association changes.
+The 2.5 release is planned to be the last major release in the 2.x series.
+After this release a `2.x` branch will be created to provide stable long-term
+support, and the `main` branch will switch to focusing on more radical changes
+for the 3.x series.
+
+Reminder for users of the library interface - the API is not designed to be
+stable across versions, and this release is not compatible with earlier 2.x
+releases. Please update and rebuild your client-side code using the updated
+`astcenc.h` header.
**General:**
* **Feature:** The `ISA_INVARIANCE` build option is no longer supported, as
there is no longer any performance benefit from the variant paths. All
- builds are now using the equivalent of the `ISA_INVARIANCE=ON` setting.
+ builds are now using the equivalent of the `ISA_INVARIANCE=ON` setting, and
+ all builds are now believed to be invariant across operating systems,
+ compilers, CPU architectures, and SIMD instruction sets.
+* **Core API:**
+ * **API Change:** The core API has been changed to be a pure C API, making it
+ easier to wrap the codec in a stable shared library ABI. Some entry points
+ that used to accept references now expect pointers.
+ * **API Change:** The decompression functionality in the core API has been
+ changed to allow use of multiple threads. The design pattern matches the
+ compression functionality, requiring the caller to create the threads,
+ synchronize them between images, and call the new
+ `astcenc_decompress_reset()` function between images.
+ * **API Feature:** Defines to support exporting public API entry point
+ symbols from a shared object are provided, but not exposed off-the-shelf by
+ the CMake provided by the project.
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## 2.4
