update readme to explain the feature gl and the new cpu only default
@@ -32,9 +32,21 @@ Wrappers for functions that take callbacks and virtual classes are not supported
Skia-safe supports the following features that can be configured [via cargo](https://doc.rust-lang.org/cargo/reference/manifest.html#the-features-section):
+### `gl`
+
+Platform support for OpenGL or OpenGL ES can be enabled by enabling the feature `gl`. Since version `0.25.0`, rust-skia is configured by default to enable CPU rendering only. Before that, OpenGL support was included in every feature configuration. To render the examples with OpenGL, use
+
+```bash
+(cd skia-safe && cargo run --features gl --example skia-org -- [OUTPUT_DIR] --driver opengl)
+```
+
### `vulkan`
-Vulkan support can be enabled by setting the Cargo feature `default = ["vulkan"]` in `skia-safe/Cargo.toml`, which will cause a rebuild of Skia. To render the examples with Vulkan use `cargo run --example skia-org -- [OUTPUT_DIR] --driver vulkan`.
+Vulkan support can be enabled by enabling the feature `vulkan`. To render the examples with Vulkan, use
+
+```bash
+(cd skia-safe && cargo run --features vulkan --example skia-org -- [OUTPUT_DIR] --driver bulkan)
+```
Note that Vulkan drivers need to be available. On Windows, they are most likely available already, on Linux [this article on linuxconfig.org](<https://linuxconfig.org/install-and-test-vulkan-on-linux>) might get you started, and on macOS with Metal support, [install the Vulkan SDK](<https://vulkan.lunarg.com/sdk/home>) for Mac and configure MoltenVK by setting the `DYLD_LIBRARY_PATH`, `VK_LAYER_PATH`, and `VK_ICD_FILENAMES` environment variables as described in `Documentation/getting_started_macos.html`.
