rhi: Include resource count in srb layout compatibility checks

Relevant for Vulkan, given that descriptorCount is part of
VkDescriptorSetLayoutBinding, meaning two srbs with arrays of
SampledTextures should only be reported as compatible if the
array size matches.

Also reduces the prealloc size for the VLAs. For Qt Quick even a
lower number would be sufficient, but we still keep the number
something fairly high in order to play nice with Quick3D.

Pick-to: 6.2
Change-Id: Id92b7c09b051ebe54b1fa2bf4ba78950fe60ba27
Reviewed-by: Andy Nichols <andy.nichols@qt.io>

1 files changed, 9 insertions, 4 deletions

diff --git a/src/gui/rhi/qrhi.cpp b/src/gui/rhi/qrhi.cpp
index b9cf0a1a36..228fc91ce3 100644
--- a/src/gui/rhi/qrhi.cpp
+++ b/src/gui/rhi/qrhi.cpp
@@ -3044,9 +3044,11 @@ void QRhiImplementation::updateLayoutDesc(QRhiShaderResourceBindings *srb)
     srb->m_layoutDesc.clear();
     for (const QRhiShaderResourceBinding &b : qAsConst(srb->m_bindings)) {
         const QRhiShaderResourceBinding::Data *d = b.data();
-        // must match QRhiShaderResourceBinding::isLayoutCompatible()
-        srb->m_layoutDescHash ^= uint(d->binding) ^ uint(d->stage) ^ uint(d->type);
-        srb->m_layoutDesc << uint(d->binding) << uint(d->stage) << uint(d->type);
+        // the logic must match QRhiShaderResourceBinding::isLayoutCompatible()
+        const int count = d->type == QRhiShaderResourceBinding::SampledTexture ? d->u.stex.count : 1;
+        // the number of entries here should match LAYOUT_DESC_FIELD_COUNT
+        srb->m_layoutDescHash ^= uint(d->binding) ^ uint(d->stage) ^ uint(d->type) ^ uint(count);
+        srb->m_layoutDesc << uint(d->binding) << uint(d->stage) << uint(d->type) << uint(count);
     }
 }
 
@@ -3110,7 +3112,10 @@ void QRhiImplementation::updateLayoutDesc(QRhiShaderResourceBindings *srb)
  */
 bool QRhiShaderResourceBinding::isLayoutCompatible(const QRhiShaderResourceBinding &other) const
 {
-    return d.binding == other.d.binding && d.stage == other.d.stage && d.type == other.d.type;
+    // i.e. everything that goes into a VkDescriptorSetLayoutBinding must match
+    const int thisCount = d.type == QRhiShaderResourceBinding::SampledTexture ? d.u.stex.count : 1;
+    const int otherCount = other.d.type == QRhiShaderResourceBinding::SampledTexture ? other.d.u.stex.count : 1;
+    return d.binding == other.d.binding && d.stage == other.d.stage && d.type == other.d.type && thisCount == otherCount;
 }
 
 /*!