VuIkan: invalid Dynamic Rendering functions from the Instance-level loader about imgui HOT 3 OPEN

Just as I pressed publish, another find:

While this can be a long discussion I decided to avoid modifying ImGui files and tried to settle with handling such cases via the callback. I give priority to loading device-level functions and if I fail, fallback to instance-level functions.

Spoiler: it didn't help. vkBeginRenderingKHR and vkEndRenderingKHR could not be found in device, so they're still requested from the instance.

But I found another difference in regards of obtaining vulkan functions:

ImGui uses KHR variant

While my ImportTable uses clean variant

So I returned to imgui_impl_vulkan.cpp and removed KHR postfix in the strings for Begin/End rendering and we're golden! Functions successfully obtained from the device

Note: For my app I create Vulkan 1.3 instance and have validation layers enabled for it

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Because it can be very setup-specific, here's my Vulkan SDK version, driver and related hardware:

Vulkan SDK: 1.3.261.0
Nvidia GeForce RTX 3070
Driver version: 543.33

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Hello,

Thanks for the careful report! Dealing with fringe backend-related issues, and in particular Vulkan ones, has been too time consuming so for now I haven't really read this.
The (unfortunate :) goal is that the vulkan backend should ideally work for everyone in every condition.

I am open to PR with solution given than you carefully research the reason current things are in place this way (you can generally use git blame). The trail gives: 121072c, 7812e83, #5446, #5037, see discussions in those threads.

Thank you!

So I have defines that force ImGui to do almost the same thing:
#define IMGUI_IMPL_VULKAN_HAS_DYNAMIC_RENDERING

FYI you shouldn't need to define this, it's defined automatically when the Vulkan header version has it.

Is it worth providing Device-level function loading?

Unless I am mistaken, in your specific configuration IMGUI_IMPL_VULKAN_USE_LOADER will NOT be defined, therefore this code in imgui_impl_vulkan never runs:

ImGuiImplVulkanFuncs_vkCmdBeginRenderingKHR = reinterpret_cast<PFN_vkCmdBeginRenderingKHR>(vkGetInstanceProcAddr(info->Instance, "vkCmdBeginRenderingKHR"));
ImGuiImplVulkanFuncs_vkCmdEndRenderingKHR = reinterpret_cast<PFN_vkCmdEndRenderingKHR>(vkGetInstanceProcAddr(info->Instance, "vkCmdEndRenderingKHR"));

Therefore the only function loading code that runs is through your loader?
I am right? In that case it wouldn't be of any use if those two lines where complemented with the equivalent call to vkGetDeviceProcAddr() ?

So I returned to imgui_impl_vulkan.cpp and removed KHR postfix in the strings for Begin/End rendering and we're golden! Functions successfully obtained from the device

I noticed by looking at your screenshots that your version of the code is before b720c0f. This was meant to solve another issue but it interfere in same places of the code making this a little confusion.

• 1. Could you update to latest?
• 2. Then confirm things based on latest and help decide what we can do in the backend to fix this for you?

Thanks a lot!

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