Custom syntax highlighting: highlight match following keyword

Question

This question might be related to Custom syntax highlighting: highlight word following keyword but after studying that for hours, I could not get it to work.

What I want is to highlight vulkan types that match vk::(Instance|Device) (in reality a much longer expression, but this will do as example).

It should not match vk::InstanceCreateInfo (because that is a different type). It should work when this match is contained inside a unrelated region. For example, I have a very complex regions that match parenthesis for different type of things; so complex that I really don't want this to be added as exception too. Yet, the highlight should work in code like:

void setup(vk::Instance vh_instance, vk::SurfaceKHR surface, DeviceCreateInfo&& device_create_info);

Aka, work while contained inside region cParen.

I already have:

syn keyword cwNamespaceTag vk

which is auto-generated; I'd prefer to be able to leave that alone. But if necessary it can be changed.

I tried the following (already changing the above keyword):

syn keyword cwNamespaceVkTag vk nextgroup=cwVulkanHandle
syn match cwVulkanHandle '\v::(Instance|Device)>' contained

but that fails in that ::Device in

void setup(foo::Device foo);

is highlighted (because it is contained (in cParen). Obviously this is not what I want; cwVulkanHandle should only be enabled when immediately following cwNamespaceVkTag.

I also tried,

syn keyword cwNamespaceVkTag vk contained
syn match cwVulkanHandle '\v<vk::(Instance|Device)>' contains=cwNamespaceVkTag

but that highlights vk (as cwNamespaceVkTag) and then cwVulkanHandle isn't used anymore for some reason. When I remove the keyword line then the match works. It seems that the fact that vk already matches a keyword stops the region from matching against it, despite that I say that it contains it.

How can I get this to work?

EDIT:

This,

syn match cwNamespaceVkTag /vk::\(Instance\|Device\)\>/ contains=cwVulkanHandle
syn match cwVulkanHandle /::\w\+/ contained

leads to

Answer 1

How about this?

syn region cParen start=/setup(/ end=/)/ contains=cwNamespaceVkTag
syn match cwNamespaceVkTag /\<vk::\(Instance\|Device\)\>/ contains=cwVulkanHandle contained
syn match cwVulkanHandle /::\w\+/ contained

I didn't use the \v (very magic) atom because I'm more used to Vim's "standard" regular expression format.

Answer 2

I moved on, after hacking something together that works for now:

" Add syntax group for vulkan types that are handles.

" The regular expression was generated with:
" RE=$(egrep '^(VK_DEFINE_NON_DISPATCHABLE_HANDLE|VK_DEFINE_HANDLE)' Vulkan-Hpp/Vulkan-Headers/include/vulkan/vulkan_core.h | sed -e 's/.*(\([^)]*\)).*/\1/;s/^Vk//' | sort | awk '{ printf("%s|", $0); }' | sed -e 's/^/(/;s/|$/)/')
syn match cwNameSpaceTag "\v<vk>"
syn match cwVulkanHandle "\v<vk::(AccelerationStructureKHR|AccelerationStructureNV|Buffer|BufferView|CommandBuffer|CommandPool|CuFunctionNVX|CuModuleNVX|DebugReportCallbackEXT|DebugUtilsMessengerEXT|DeferredOperationKHR|DescriptorPool|DescriptorSet|DescriptorSetLayout|DescriptorUpdateTemplate|Device|DeviceMemory|DisplayKHR|DisplayModeKHR|Event|Fence|Framebuffer|Image|ImageView|IndirectCommandsLayoutNV|Instance|PerformanceConfigurationINTEL|PhysicalDevice|Pipeline|PipelineCache|PipelineLayout|PrivateDataSlotEXT|QueryPool|Queue|RenderPass|Sampler|SamplerYcbcrConversion|Semaphore|ShaderModule|SurfaceKHR|SwapchainKHR|ValidationCacheEXT)>"hs=s+4 contains=cwNamespaceTag
syn match cwVulkanHandle "\v<Vk(AccelerationStructureKHR|AccelerationStructureNV|Buffer|BufferView|CommandBuffer|CommandPool|CuFunctionNVX|CuModuleNVX|DebugReportCallbackEXT|DebugUtilsMessengerEXT|DeferredOperationKHR|DescriptorPool|DescriptorSet|DescriptorSetLayout|DescriptorUpdateTemplate|Device|DeviceMemory|DisplayKHR|DisplayModeKHR|Event|Fence|Framebuffer|Image|ImageView|IndirectCommandsLayoutNV|Instance|PerformanceConfigurationINTEL|PhysicalDevice|Pipeline|PipelineCache|PipelineLayout|PrivateDataSlotEXT|QueryPool|Queue|RenderPass|Sampler|SamplerYcbcrConversion|Semaphore|ShaderModule|SurfaceKHR|SwapchainKHR|ValidationCacheEXT)>"

hi def link cwVulkanHandle cVulkanHandle                    " Highlight vulkan handle types.

For this to work I also had to make sure that the previous keyword rule for vk was no longer generated.

Or as short version that we used here as example / test case:

syn match cwNameSpaceTag "\v<vk>"
syn match cwVulkanHandle "\v<vk::(Instance|Device)>"hs=s+4 contains=cwNamespaceTag

The main trick here is using a match for the namespace vk instead of a keyword. Apparently a keyword always has a higher precedence, so when that exists you can not add a match that contains it. By using another match it works: when the match that follow the first one matches, it become the one that is picked, overruling the first more general match.

My conclusion is that vim's highlighting interface needs a rewrite: for most things that are just a little bit more advanced one quickly has to resort to hacks and far from intuitive. I suppose that the preferred method (for C++) would be one that is based of llvm (clang).

Things that I ran into:

1. It is not possible to delete/remove a rule later on (ie, a keyword rule).
2. It is not possible to explicitly state that rule should ONLY match when contained in LIST, automatically avoiding any existing rules with a contains=ALL_BUT,... without having to add to each and every such list.
3. I could not figure out how (seems not possible) to match a start pattern against text that was already matched (vk::), which made it impossible to even begin to use regions here.