rhi: Expose the maximum uniform buffer range limit

Pick-to: 6.2
Task-number: QTBUG-97715
Change-Id: I7f0a52c410b9b77f735fb3b7fd33141674bb0cda
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Andy Nichols <andy.nichols@qt.io>

1 files changed, 15 insertions, 0 deletions

diff --git a/src/gui/rhi/qrhi.cpp b/src/gui/rhi/qrhi.cpp
index efa3c1893d..952183f55e 100644
--- a/src/gui/rhi/qrhi.cpp
+++ b/src/gui/rhi/qrhi.cpp
@@ -776,6 +776,12 @@ Q_LOGGING_CATEGORY(QRHI_LOG_INFO, "qt.rhi.general")
     \value TextureArraySizeMax Maximum texture array size. Typically in range
     256 - 2048. Attempting to \l{QRhi::newTextureArray()}{create a texture
     array} with more elements will likely fail.
+
+    \value MaxUniformBufferRange The number of bytes that can be exposed from a
+    uniform buffer to the shaders at once. On OpenGL ES 2.0 and 3.0
+    implementations this may be as low as 3584 bytes (224 four component, 32
+    bits per component vectors). Elsewhere the value is typically 16384 (1024
+    vec4s) or 65536 (4096 vec4s).
  */
 
 /*!
@@ -3228,6 +3234,9 @@ bool QRhiShaderResourceBinding::isLayoutCompatible(const QRhiShaderResourceBindi
     suitable for creating pipelines. Such a pipeline must then always be used
     together with another, layout compatible QRhiShaderResourceBindings with
     resources present passed to QRhiCommandBuffer::setShaderResources().
+
+    \note If the size of \a buf exceeds the limit reported for
+    QRhi::MaxUniformBufferRange, unexpected errors may occur.
  */
 QRhiShaderResourceBinding QRhiShaderResourceBinding::uniformBuffer(
         int binding, StageFlags stage, QRhiBuffer *buf)
@@ -3262,6 +3271,9 @@ QRhiShaderResourceBinding QRhiShaderResourceBinding::uniformBuffer(
     suitable for creating pipelines. Such a pipeline must then always be used
     together with another, layout compatible QRhiShaderResourceBindings with
     resources present passed to QRhiCommandBuffer::setShaderResources().
+
+    \note If \a size exceeds the limit reported for QRhi::MaxUniformBufferRange,
+    unexpected errors may occur.
  */
 QRhiShaderResourceBinding QRhiShaderResourceBinding::uniformBuffer(
         int binding, StageFlags stage, QRhiBuffer *buf, int offset, int size)
@@ -3296,6 +3308,9 @@ QRhiShaderResourceBinding QRhiShaderResourceBinding::uniformBuffer(
     suitable for creating pipelines. Such a pipeline must then always be used
     together with another, layout compatible QRhiShaderResourceBindings with
     resources present passed to QRhiCommandBuffer::setShaderResources().
+
+    \note If \a size exceeds the limit reported for QRhi::MaxUniformBufferRange,
+    unexpected errors may occur.
  */
 QRhiShaderResourceBinding QRhiShaderResourceBinding::uniformBufferWithDynamicOffset(
         int binding, StageFlags stage, QRhiBuffer *buf, int size)