[Fix] (MG_Backend/DirectVulkan): materialize mid-pass pending color clears at the subpass color slot index, not the compacted description index

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)
                         });
                     }

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;

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(),