GH-1345 Simplify Vulkan check logic

[JoltedJon]

Resolves #1345

The checking logic I originally implemented did not take into account OpenXR which needs to handle it's own vulkan devices. This keeps some of the logic without initializing any vulkan devices.

Summary by CodeRabbit

• Bug Fixes
  • Improved Vulkan support detection for faster, more reliable startup.
  • Corrected the OpenXR initialization error message to reference Redot when falling back to normal mode.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Team

Run ID: 445f4e74-68f4-48c6-9cc2-050982a7f0b1

📥 Commits

Reviewing files that changed from the base of the PR and between 335d159 and 6552290.

📒 Files selected for processing (2)

• drivers/vulkan/rendering_context_driver_vulkan.cpp
• modules/openxr/register_types.cpp

Included review availability: Your plan provides up to 8 included reviews per hour; 7 remain after this review.

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Walkthrough

The Vulkan support check no longer creates a probe instance or enumerates physical devices. With USE_VOLK, it checks volk initialization and vkGetInstanceProcAddr. The OpenXR initialization failure message now refers to Redot.

Changes

Vulkan support detection

Layer / File(s)	Summary
Simplify Vulkan availability checks drivers/vulkan/rendering_context_driver_vulkan.cpp	_vulkan_is_supported() removes VulkanHooks and probe-instance checks. With USE_VOLK, it initializes volk and verifies vkGetInstanceProcAddr.

OpenXR initialization message

Layer / File(s)	Summary
Update initialization failure text modules/openxr/register_types.cpp	The fallback message now says “Redot will start in normal mode”.

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: 🔵 Low · up to 65522

The change simplifies Vulkan/OpenXR startup checks without bypassing final device validation. If device acquisition fails after instance creation, a failed rendering context may retain partial Vulkan state until it is destroyed; this appears bounded but warrants owner awareness or follow-up cleanup.

Suggested reviewers: mcdubhghlas, generalprotectionfault

🚥 Pre-merge checks | ✅ 3 | ❌ 2

❌ Failed checks (2 warnings)

Check name	Status	Explanation	Resolution
Out of Scope Changes check	⚠️ Warning	The OpenXR message change from "Godot will start in normal mode" to "Redot will start in normal mode" is unrelated to the Vulkan logic required by issue #1345.	Remove the unrelated OpenXR message change, or link an issue that requires the branding correction.
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 3 functions across 2 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly identifies the main change: simplifying Vulkan support-check logic.
Linked Issues check	✅ Passed	The Vulkan change removes temporary Vulkan instance and physical-device initialization while retaining the volk availability check. This directly supports OpenXR device management and addresses issue …

Full details: Linked Issues check

Explanation

The Vulkan change removes temporary Vulkan instance and physical-device initialization while retaining the volk availability check. This directly supports OpenXR device management and addresses issue #1345, which reports null rendering devices when OpenXR is enabled.

• Fix all pre-merge checks with AI

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[DaveTheEggman]

LGTM from the rendering side

[Arctis-Fireblight]

LGTM