* Bump API patch number and header version number to 68 for this update.
Github Issues:
* Added more details in the
<<extended-functionality-extensions-compatibility, Extension
Compatibility>> section, allowing explicit incompatibilities, and
simplify corresponding language in the style guide, which now defers to
the API Specification on this point (public issue 638).
* Fix typo in description of slink:VkCommandBufferLevel::pname:level
(public issue 651).
* Only include extension-dependent valid usage statement for
slink:VkImageSubresourceRange, and note that the extension names for
header files described in the <<boilerplate-wsi-header, Window
System-Specific Header Control>> section are only valid links, when the
specification being viewed is built with the corresponding extensions
enabled (public issue 652).
Internal Issues:
* Add language to elink:VkResult specifying that when commands return an
error, output parameter contents are undefined instead of unmodified
(except for pname:sType and pname:pNext). Note that this is a behavior
change. Add notes calling out slink:VkImageFormatProperties as an
exception (internal issue 1118).
* Add "`general-purpose`" to the style guide, and correct existing uses of
"`general purpose`" as an adjective (internal issue 1121).
* Add the ename:VK_DEBUG_REPORT_OBJECT_TYPE_VALIDATION_CACHE_EXT_EXT token
for the `VK_EXT_validation_cache` extension, following the same naming
pattern as other tokens in the extension, but keep the old
ename:VK_DEBUG_REPORT_OBJECT_TYPE_VALIDATION_CACHE_EXT token around for
backwards compatibility (internal issue 1126).
Other Issues:
* Specify that flink:vkCmdSetDiscardRectangleEXT does not affect copies or
clears, matching existing language for the scissor rectangle test.
* Move the <<boilerplate-sType, pname:sType>> definition from the
boilerplate appendix to the Fundamentals chapter, putting it together
with the valid usage of pname:sType rather than having the definition
split across two places.
* Inline all of the etext:Vk*Flags definitions, moving each one from the
boilerplate appendix to appear either after the corresponding
etext:Vk*FlagBits value if one is defined, or after the first structure
that includes them if not.