Document recommendations and limitations of automatic layout creation (…

…vulkano-rs#2282)

vulkano/src/pipeline/layout.rs

@@ -902,6 +902,33 @@ pub struct PipelineDescriptorSetLayoutCreateInfo {
 impl PipelineDescriptorSetLayoutCreateInfo {
  /// Creates a new `PipelineDescriptorSetLayoutCreateInfo` from the union of the requirements of
  /// each shader stage in `stages`.
+ ///
+ /// This is intended for quick prototyping or for single use layouts that do not have any
+ /// bindings in common with other shaders. For the general case, it is strongly recommended
+ /// to create pipeline layouts manually:
+ /// - When multiple pipelines share the same layout object, it is faster than if they have
+ /// different objects, even if the objects both contain identical bindings. It is also faster
+ /// (though a little bit less), if multiple pipeline layout objects share common descriptor
+ /// set objects.
+ /// - Pipeline layouts only need to be a superset of what the shaders use, they don't have to
+ /// match exactly. Creating a manual pipeline layout therefore allows you to specify layouts
+ /// that are applicable for many shaders, as long as each one uses a subset. This allows
+ /// further sharing.
+ /// - Creating a manual pipeline layout makes your code more robust against changes in the
+ /// shader, in particular regarding whether a particular binding in the shader is used or not
+ /// (see also the limitations below).
+ ///
+ /// # Limitations:
+ ///
+ /// Only bindings that are [statically used] are included in the descriptor binding
+ /// requirements, and therefore are included in the descriptor set layout.
+ /// If the use of a binding depends on input variables to the shader (buffers, images,
+ /// push constants etc.) then the shader reflection is unable to know that the binding is in
+ /// use, and it will not be included in the pipeline layout.
+ ///
+ /// Note that this corresponds to the `shader_*_array_dynamic_indexing` device features.
+ ///
+ /// [statically used]: https://registry.khronos.org/vulkan/specs/1.3-extensions/html/vkspec.html#shaders-staticuse
  pub fn from_stages<'a>(
  stages: impl IntoIterator<Item = &'a PipelineShaderStageCreateInfo>,
  ) -> Self {