From 37ef2cb600af2c7534f15466e501dbf487c4351c Mon Sep 17 00:00:00 2001
From: Swung0x48 <swung0x48@outlook.com>
Date: Thu, 16 Jul 2026 19:13:25 -0400
Subject: [PATCH] [Fix] (MG_Backend/DirectVulkan): materialize mid-pass pending
 color clears at the subpass color slot index, not the compacted description
 index

---
 .../MG_Backend/DirectVulkan/Renderer/VkRenderPassManager.cpp | 1 +
 .../MG_Backend/DirectVulkan/Renderer/VkRenderPassManager.h   | 5 +++++
 MobileGL/MG_Backend/DirectVulkan/Renderer/VulkanRenderer.cpp | 4 +++-
 3 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/MobileGL/MG_Backend/DirectVulkan/Renderer/VkRenderPassManager.cpp b/MobileGL/MG_Backend/DirectVulkan/Renderer/VkRenderPassManager.cpp
index 143e2412..9a6ca4ce 100644
--- a/MobileGL/MG_Backend/DirectVulkan/Renderer/VkRenderPassManager.cpp
+++ b/MobileGL/MG_Backend/DirectVulkan/Renderer/VkRenderPassManager.cpp
@@ -718,6 +718,7 @@ namespace MobileGL::MG_Backend::DirectVulkan {
                     if (hasClear) {
                         pendingClearAttachments.emplace_back(PendingClearAttachmentInfo {
                             .attachmentIndex = attachmentIndex,
+                            .colorAttachmentSlot = i,
                             .key = VkClearManager::MakePendingClearKey(att)
                         });
                     }
diff --git a/MobileGL/MG_Backend/DirectVulkan/Renderer/VkRenderPassManager.h b/MobileGL/MG_Backend/DirectVulkan/Renderer/VkRenderPassManager.h
index 7364dc46..7fe370a6 100644
--- a/MobileGL/MG_Backend/DirectVulkan/Renderer/VkRenderPassManager.h
+++ b/MobileGL/MG_Backend/DirectVulkan/Renderer/VkRenderPassManager.h
@@ -27,7 +27,12 @@ namespace MobileGL::MG_Backend::DirectVulkan {
     };
 
     struct PendingClearAttachmentInfo {
+        // Index into the render pass attachment descriptions (VkRenderPassBeginInfo::pClearValues space).
         Uint32 attachmentIndex = 0;
+        // Index into the subpass pColorAttachments (VkClearAttachment::colorAttachment space) — the GL
+        // draw-buffer slot. Differs from attachmentIndex when earlier slots are GL_NONE/incomplete.
+        // Only meaningful for color clears.
+        Uint32 colorAttachmentSlot = 0;
         PendingClearKey key{};
         MG_State::GLState::RenderbufferObject* renderbuffer = nullptr;
         Bool hasInlinePayload = false;
diff --git a/MobileGL/MG_Backend/DirectVulkan/Renderer/VulkanRenderer.cpp b/MobileGL/MG_Backend/DirectVulkan/Renderer/VulkanRenderer.cpp
index a10f7fd6..973cfdc7 100644
--- a/MobileGL/MG_Backend/DirectVulkan/Renderer/VulkanRenderer.cpp
+++ b/MobileGL/MG_Backend/DirectVulkan/Renderer/VulkanRenderer.cpp
@@ -6908,7 +6908,9 @@ void main() {
             clearAttachment.clearValue.depthStencil = {1.0f, 0};
             if ((clearPayload.mask & GL_COLOR_BUFFER_BIT) != 0) {
                 clearAttachment.aspectMask = VK_IMAGE_ASPECT_COLOR_BIT;
-                clearAttachment.colorAttachment = pending.attachmentIndex;
+                // VkClearAttachment::colorAttachment indexes the subpass pColorAttachments (draw-buffer
+                // slot space, with UNUSED holes), not the compacted attachment descriptions.
+                clearAttachment.colorAttachment = pending.colorAttachmentSlot;
                 clearAttachment.clearValue.color = {
                         clearPayload.color.x(),
                         clearPayload.color.y(),