rhi: Add backing format hint to QRhiRenderBuffer

Task-number: QTBUG-83707
Change-Id: I63548f4ace70af614a2aa082663bb3ae9fbedc25
Reviewed-by: Paul Olav Tvete <paul.tvete@qt.io>

src/gui/rhi/qrhi.cpp

@@ -2123,9 +2123,11 @@ QRhiBuffer::NativeBuffer QRhiBuffer::nativeBuffer()
     \internal
  */
 QRhiRenderBuffer::QRhiRenderBuffer(QRhiImplementation *rhi, Type type_, const QSize &pixelSize_,
-                                   int sampleCount_, Flags flags_)
+                                   int sampleCount_, Flags flags_,
+                                   QRhiTexture::Format backingFormatHint_)
     : QRhiResource(rhi),
-      m_type(type_), m_pixelSize(pixelSize_), m_sampleCount(sampleCount_), m_flags(flags_)
+      m_type(type_), m_pixelSize(pixelSize_), m_sampleCount(sampleCount_), m_flags(flags_),
+      m_backingFormatHint(backingFormatHint_)
 {
 }
 
@@ -5488,14 +5490,29 @@ QRhiBuffer *QRhi::newBuffer(QRhiBuffer::Type type,
     \return a new renderbuffer with the specified \a type, \a pixelSize, \a
     sampleCount, and \a flags.
 
+    When \a backingFormatHint is set to a texture format other than
+    QRhiTexture::UnknownFormat, it may be used by the backend to decide what
+    format to use for the storage backing the renderbuffer.
+
+    \note \a backingFormatHint becomes relevant typically when multisampling
+    and floating point texture formats are involved: rendering into a
+    multisample QRhiRenderBuffer and then resolving into a non-RGBA8
+    QRhiTexture implies (with some graphics APIs) that the storage backing the
+    QRhiRenderBuffer uses the matching non-RGBA8 format. That means that
+    passing a format like QRhiTexture::RGBA32F is important, because backends
+    will typically opt for QRhiTexture::RGBA8 by default, which would then
+    break later on due to attempting to set up RGBA8->RGBA32F multisample
+    resolve in the color attachment(s) of the QRhiTextureRenderTarget.
+
     \sa QRhiResource::release()
  */
 QRhiRenderBuffer *QRhi::newRenderBuffer(QRhiRenderBuffer::Type type,
                                         const QSize &pixelSize,
                                         int sampleCount,
-                                        QRhiRenderBuffer::Flags flags)
+                                        QRhiRenderBuffer::Flags flags,
+                                        QRhiTexture::Format backingFormatHint)
 {
-    return d->createRenderBuffer(type, pixelSize, sampleCount, flags);
+    return d->createRenderBuffer(type, pixelSize, sampleCount, flags, backingFormatHint);
 }
 
 /*!

src/gui/rhi/qrhi_p.h

@@ -908,11 +908,12 @@ public:
 
 protected:
     QRhiRenderBuffer(QRhiImplementation *rhi, Type type_, const QSize &pixelSize_,
-                     int sampleCount_, Flags flags_);
+                     int sampleCount_, Flags flags_, QRhiTexture::Format backingFormatHint_);
     Type m_type;
     QSize m_pixelSize;
     int m_sampleCount;
     Flags m_flags;
+    QRhiTexture::Format m_backingFormatHint;
 };
 
 Q_DECLARE_OPERATORS_FOR_FLAGS(QRhiRenderBuffer::Flags)
@@ -1493,7 +1494,8 @@ public:
     QRhiRenderBuffer *newRenderBuffer(QRhiRenderBuffer::Type type,
                                       const QSize &pixelSize,
                                       int sampleCount = 1,
-                                      QRhiRenderBuffer::Flags flags = QRhiRenderBuffer::Flags());
+                                      QRhiRenderBuffer::Flags flags = QRhiRenderBuffer::Flags(),
+                                      QRhiTexture::Format backingFormatHint = QRhiTexture::UnknownFormat);
 
     QRhiTexture *newTexture(QRhiTexture::Format format,
                             const QSize &pixelSize,

src/gui/rhi/qrhi_p_p.h

@@ -80,7 +80,8 @@ public:
     virtual QRhiRenderBuffer *createRenderBuffer(QRhiRenderBuffer::Type type,
                                                  const QSize &pixelSize,
                                                  int sampleCount,
-                                                 QRhiRenderBuffer::Flags flags) = 0;
+                                                 QRhiRenderBuffer::Flags flags,
+                                                 QRhiTexture::Format backingFormatHint) = 0;
     virtual QRhiTexture *createTexture(QRhiTexture::Format format,
                                        const QSize &pixelSize,
                                        int sampleCount,

src/gui/rhi/qrhid3d11.cpp

@@ -528,9 +528,10 @@ bool QRhiD3D11::isDeviceLost() const
 }
 
 QRhiRenderBuffer *QRhiD3D11::createRenderBuffer(QRhiRenderBuffer::Type type, const QSize &pixelSize,
-                                                int sampleCount, QRhiRenderBuffer::Flags flags)
+                                                int sampleCount, QRhiRenderBuffer::Flags flags,
+                                                QRhiTexture::Format backingFormatHint)
 {
-    return new QD3D11RenderBuffer(this, type, pixelSize, sampleCount, flags);
+    return new QD3D11RenderBuffer(this, type, pixelSize, sampleCount, flags, backingFormatHint);
 }
 
 QRhiTexture *QRhiD3D11::createTexture(QRhiTexture::Format format, const QSize &pixelSize,
@@ -2613,8 +2614,9 @@ ID3D11UnorderedAccessView *QD3D11Buffer::unorderedAccessView()
 }
 
 QD3D11RenderBuffer::QD3D11RenderBuffer(QRhiImplementation *rhi, Type type, const QSize &pixelSize,
-                                       int sampleCount, QRhiRenderBuffer::Flags flags)
+                                       int sampleCount, QRhiRenderBuffer::Flags flags,
-    : QRhiRenderBuffer(rhi, type, pixelSize, sampleCount, flags)
+                                       QRhiTexture::Format backingFormatHint)
+    : QRhiRenderBuffer(rhi, type, pixelSize, sampleCount, flags, backingFormatHint)
 {
 }
 
@@ -2668,7 +2670,8 @@ bool QD3D11RenderBuffer::build()
     desc.Usage = D3D11_USAGE_DEFAULT;
 
     if (m_type == Color) {
-        dxgiFormat = DXGI_FORMAT_R8G8B8A8_UNORM;
+        dxgiFormat = m_backingFormatHint == QRhiTexture::UnknownFormat ? DXGI_FORMAT_R8G8B8A8_UNORM
+                                                                       : toD3DTextureFormat(m_backingFormatHint, {});
         desc.Format = dxgiFormat;
         desc.BindFlags = D3D11_BIND_RENDER_TARGET;
         HRESULT hr = rhiD->dev->CreateTexture2D(&desc, nullptr, &tex);
@@ -2721,7 +2724,10 @@ bool QD3D11RenderBuffer::build()
 
 QRhiTexture::Format QD3D11RenderBuffer::backingFormat() const
 {
-    return m_type == Color ? QRhiTexture::RGBA8 : QRhiTexture::UnknownFormat;
+    if (m_backingFormatHint != QRhiTexture::UnknownFormat)
+        return m_backingFormatHint;
+    else
+        return m_type == Color ? QRhiTexture::RGBA8 : QRhiTexture::UnknownFormat;
 }
 
 QD3D11Texture::QD3D11Texture(QRhiImplementation *rhi, Format format, const QSize &pixelSize,

src/gui/rhi/qrhid3d11_p_p.h

@@ -79,7 +79,8 @@ struct QD3D11Buffer : public QRhiBuffer
 struct QD3D11RenderBuffer : public QRhiRenderBuffer
 {
     QD3D11RenderBuffer(QRhiImplementation *rhi, Type type, const QSize &pixelSize,
-                       int sampleCount, QRhiRenderBuffer::Flags flags);
+                       int sampleCount, QRhiRenderBuffer::Flags flags,
+                       QRhiTexture::Format backingFormatHint);
     ~QD3D11RenderBuffer();
     void release() override;
     bool build() override;
@@ -567,7 +568,8 @@ public:
     QRhiRenderBuffer *createRenderBuffer(QRhiRenderBuffer::Type type,
                                          const QSize &pixelSize,
                                          int sampleCount,
-                                         QRhiRenderBuffer::Flags flags) override;
+                                         QRhiRenderBuffer::Flags flags,
+                                         QRhiTexture::Format backingFormatHint) override;
     QRhiTexture *createTexture(QRhiTexture::Format format,
                                const QSize &pixelSize,
                                int sampleCount,

src/gui/rhi/qrhigles2.cpp

@@ -690,6 +690,87 @@ static inline GLenum toGlCompressedTextureFormat(QRhiTexture::Format format, QRh
     }
 }
 
+static inline void toGlTextureFormat(QRhiTexture::Format format, const QRhiGles2::Caps &caps,
+                                     GLenum *glintformat, GLenum *glsizedintformat,
+                                     GLenum *glformat, GLenum *gltype)
+{
+    switch (format) {
+    case QRhiTexture::RGBA8:
+        *glintformat = GL_RGBA;
+        *glsizedintformat = caps.rgba8Format ? GL_RGBA8 : GL_RGBA;
+        *glformat = GL_RGBA;
+        *gltype = GL_UNSIGNED_BYTE;
+        break;
+    case QRhiTexture::BGRA8:
+        *glintformat = caps.bgraInternalFormat ? GL_BGRA : GL_RGBA;
+        *glsizedintformat = caps.rgba8Format ? GL_RGBA8 : GL_RGBA;
+        *glformat = GL_BGRA;
+        *gltype = GL_UNSIGNED_BYTE;
+        break;
+    case QRhiTexture::R16:
+        *glintformat = GL_R16;
+        *glsizedintformat = *glintformat;
+        *glformat = GL_RED;
+        *gltype = GL_UNSIGNED_SHORT;
+        break;
+    case QRhiTexture::R8:
+        *glintformat = GL_R8;
+        *glsizedintformat = *glintformat;
+        *glformat = GL_RED;
+        *gltype = GL_UNSIGNED_BYTE;
+        break;
+    case QRhiTexture::RED_OR_ALPHA8:
+        *glintformat = caps.coreProfile ? GL_R8 : GL_ALPHA;
+        *glsizedintformat = *glintformat;
+        *glformat = caps.coreProfile ? GL_RED : GL_ALPHA;
+        *gltype = GL_UNSIGNED_BYTE;
+        break;
+    case QRhiTexture::RGBA16F:
+        *glintformat = GL_RGBA16F;
+        *glsizedintformat = *glintformat;
+        *glformat = GL_RGBA;
+        *gltype = GL_HALF_FLOAT;
+        break;
+    case QRhiTexture::RGBA32F:
+        *glintformat = GL_RGBA32F;
+        *glsizedintformat = *glintformat;
+        *glformat = GL_RGBA;
+        *gltype = GL_FLOAT;
+        break;
+    case QRhiTexture::R16F:
+        *glintformat = GL_R16F;
+        *glsizedintformat = *glintformat;
+        *glformat = GL_RED;
+        *gltype = GL_HALF_FLOAT;
+        break;
+    case QRhiTexture::R32F:
+        *glintformat = GL_R32F;
+        *glsizedintformat = *glintformat;
+        *glformat = GL_RED;
+        *gltype = GL_FLOAT;
+        break;
+    case QRhiTexture::D16:
+        *glintformat = GL_DEPTH_COMPONENT16;
+        *glsizedintformat = *glintformat;
+        *glformat = GL_DEPTH_COMPONENT;
+        *gltype = GL_UNSIGNED_SHORT;
+        break;
+    case QRhiTexture::D32F:
+        *glintformat = GL_DEPTH_COMPONENT32F;
+        *glsizedintformat = *glintformat;
+        *glformat = GL_DEPTH_COMPONENT;
+        *gltype = GL_FLOAT;
+        break;
+    default:
+        Q_UNREACHABLE();
+        *glintformat = GL_RGBA;
+        *glsizedintformat = caps.rgba8Format ? GL_RGBA8 : GL_RGBA;
+        *glformat = GL_RGBA;
+        *gltype = GL_UNSIGNED_BYTE;
+        break;
+    }
+}
+
 bool QRhiGles2::isTextureFormatSupported(QRhiTexture::Format format, QRhiTexture::Flags flags) const
 {
     if (isCompressedFormat(format))
@@ -833,9 +914,10 @@ bool QRhiGles2::isDeviceLost() const
 }
 
 QRhiRenderBuffer *QRhiGles2::createRenderBuffer(QRhiRenderBuffer::Type type, const QSize &pixelSize,
-                                                int sampleCount, QRhiRenderBuffer::Flags flags)
+                                                int sampleCount, QRhiRenderBuffer::Flags flags,
+                                                QRhiTexture::Format backingFormatHint)
 {
-    return new QGles2RenderBuffer(this, type, pixelSize, sampleCount, flags);
+    return new QGles2RenderBuffer(this, type, pixelSize, sampleCount, flags, backingFormatHint);
 }
 
 QRhiTexture *QRhiGles2::createTexture(QRhiTexture::Format format, const QSize &pixelSize,
@@ -3435,8 +3517,9 @@ QRhiBuffer::NativeBuffer QGles2Buffer::nativeBuffer()
 }
 
 QGles2RenderBuffer::QGles2RenderBuffer(QRhiImplementation *rhi, Type type, const QSize &pixelSize,
-                                       int sampleCount, QRhiRenderBuffer::Flags flags)
+                                       int sampleCount, QRhiRenderBuffer::Flags flags,
-    : QRhiRenderBuffer(rhi, type, pixelSize, sampleCount, flags)
+                                       QRhiTexture::Format backingFormatHint)
+    : QRhiRenderBuffer(rhi, type, pixelSize, sampleCount, flags, backingFormatHint)
 {
 }
 
@@ -3522,13 +3605,26 @@ bool QGles2RenderBuffer::build()
         QRHI_PROF_F(newRenderBuffer(this, false, false, samples));
         break;
     case QRhiRenderBuffer::Color:
-        if (rhiD->caps.msaaRenderBuffer && samples > 1)
+    {
-            rhiD->f->glRenderbufferStorageMultisample(GL_RENDERBUFFER, samples, GL_RGBA8,
+        GLenum internalFormat = GL_RGBA4; // ES 2.0
+        if (rhiD->caps.rgba8Format) {
+            internalFormat = GL_RGBA8;
+            if (m_backingFormatHint != QRhiTexture::UnknownFormat) {
+                GLenum glintformat, glformat, gltype;
+                // only care about the sized internal format, the rest is not used here
+                toGlTextureFormat(m_backingFormatHint, rhiD->caps,
+                                  &glintformat, &internalFormat, &glformat, &gltype);
+            }
+        }
+        if (rhiD->caps.msaaRenderBuffer && samples > 1) {
+            rhiD->f->glRenderbufferStorageMultisample(GL_RENDERBUFFER, samples, internalFormat,
                                                       size.width(), size.height());
-        else
+        } else {
-            rhiD->f->glRenderbufferStorage(GL_RENDERBUFFER, rhiD->caps.rgba8Format ? GL_RGBA8 : GL_RGBA4,
+            rhiD->f->glRenderbufferStorage(GL_RENDERBUFFER, internalFormat,
                                            size.width(), size.height());
+        }
         QRHI_PROF_F(newRenderBuffer(this, false, false, samples));
+    }
         break;
     default:
         Q_UNREACHABLE();
@@ -3541,7 +3637,10 @@ bool QGles2RenderBuffer::build()
 
 QRhiTexture::Format QGles2RenderBuffer::backingFormat() const
 {
-    return m_type == Color ? QRhiTexture::RGBA8 : QRhiTexture::UnknownFormat;
+    if (m_backingFormatHint != QRhiTexture::UnknownFormat)
+        return m_backingFormatHint;
+    else
+        return m_type == Color ? QRhiTexture::RGBA8 : QRhiTexture::UnknownFormat;
 }
 
 QGles2Texture::QGles2Texture(QRhiImplementation *rhi, Format format, const QSize &pixelSize,
@@ -3608,76 +3707,8 @@ bool QGles2Texture::prepareBuild(QSize *adjustedSize)
         glsizedintformat = glintformat;
         glformat = GL_RGBA;
     } else {
-        switch (m_format) {
+        toGlTextureFormat(m_format, rhiD->caps,
-        case QRhiTexture::RGBA8:
+                          &glintformat, &glsizedintformat, &glformat, &gltype);
-            glintformat = GL_RGBA;
-            glsizedintformat = rhiD->caps.rgba8Format ? GL_RGBA8 : GL_RGBA;
-            glformat = GL_RGBA;
-            break;
-        case QRhiTexture::BGRA8:
-            glintformat = rhiD->caps.bgraInternalFormat ? GL_BGRA : GL_RGBA;
-            glsizedintformat = rhiD->caps.rgba8Format ? GL_RGBA8 : GL_RGBA;
-            glformat = GL_BGRA;
-            break;
-        case QRhiTexture::R16:
-            glintformat = GL_R16;
-            glsizedintformat = glintformat;
-            glformat = GL_RED;
-            gltype = GL_UNSIGNED_SHORT;
-            break;
-        case QRhiTexture::R8:
-            glintformat = GL_R8;
-            glsizedintformat = glintformat;
-            glformat = GL_RED;
-            break;
-        case QRhiTexture::RED_OR_ALPHA8:
-            glintformat = rhiD->caps.coreProfile ? GL_R8 : GL_ALPHA;
-            glsizedintformat = glintformat;
-            glformat = rhiD->caps.coreProfile ? GL_RED : GL_ALPHA;
-            break;
-        case QRhiTexture::RGBA16F:
-            glintformat = GL_RGBA16F;
-            glsizedintformat = glintformat;
-            glformat = GL_RGBA;
-            gltype = GL_HALF_FLOAT;
-            break;
-        case QRhiTexture::RGBA32F:
-            glintformat = GL_RGBA32F;
-            glsizedintformat = glintformat;
-            glformat = GL_RGBA;
-            gltype = GL_FLOAT;
-            break;
-        case QRhiTexture::R16F:
-            glintformat = GL_R16F;
-            glsizedintformat = glintformat;
-            glformat = GL_RED;
-            gltype = GL_HALF_FLOAT;
-            break;
-        case QRhiTexture::R32F:
-            glintformat = GL_R32F;
-            glsizedintformat = glintformat;
-            glformat = GL_RED;
-            gltype = GL_FLOAT;
-            break;
-        case QRhiTexture::D16:
-            glintformat = GL_DEPTH_COMPONENT16;
-            glsizedintformat = glintformat;
-            glformat = GL_DEPTH_COMPONENT;
-            gltype = GL_UNSIGNED_SHORT;
-            break;
-        case QRhiTexture::D32F:
-            glintformat = GL_DEPTH_COMPONENT32F;
-            glsizedintformat = glintformat;
-            glformat = GL_DEPTH_COMPONENT;
-            gltype = GL_FLOAT;
-            break;
-        default:
-            Q_UNREACHABLE();
-            glintformat = GL_RGBA;
-            glsizedintformat = rhiD->caps.rgba8Format ? GL_RGBA8 : GL_RGBA;
-            glformat = GL_RGBA;
-            break;
-        }
     }
 
     samplerState = QGles2SamplerData();

src/gui/rhi/qrhigles2_p_p.h

@@ -89,7 +89,8 @@ struct QGles2Buffer : public QRhiBuffer
 struct QGles2RenderBuffer : public QRhiRenderBuffer
 {
     QGles2RenderBuffer(QRhiImplementation *rhi, Type type, const QSize &pixelSize,
-                       int sampleCount, QRhiRenderBuffer::Flags flags);
+                       int sampleCount, QRhiRenderBuffer::Flags flags,
+                       QRhiTexture::Format backingFormatHint);
     ~QGles2RenderBuffer();
     void release() override;
     bool build() override;
@@ -694,7 +695,8 @@ public:
     QRhiRenderBuffer *createRenderBuffer(QRhiRenderBuffer::Type type,
                                          const QSize &pixelSize,
                                          int sampleCount,
-                                         QRhiRenderBuffer::Flags flags) override;
+                                         QRhiRenderBuffer::Flags flags,
+                                         QRhiTexture::Format backingFormatHint) override;
     QRhiTexture *createTexture(QRhiTexture::Format format,
                                const QSize &pixelSize,
                                int sampleCount,

src/gui/rhi/qrhimetal.mm

@@ -621,9 +621,10 @@ bool QRhiMetal::isDeviceLost() const
 }
 
 QRhiRenderBuffer *QRhiMetal::createRenderBuffer(QRhiRenderBuffer::Type type, const QSize &pixelSize,
-                                                int sampleCount, QRhiRenderBuffer::Flags flags)
+                                                int sampleCount, QRhiRenderBuffer::Flags flags,
+                                                QRhiTexture::Format backingFormatHint)
 {
-    return new QMetalRenderBuffer(this, type, pixelSize, sampleCount, flags);
+    return new QMetalRenderBuffer(this, type, pixelSize, sampleCount, flags, backingFormatHint);
 }
 
 QRhiTexture *QRhiMetal::createTexture(QRhiTexture::Format format, const QSize &pixelSize,
@@ -2232,149 +2233,6 @@ QRhiBuffer::NativeBuffer QMetalBuffer::nativeBuffer()
     return { { &d->buf[0] }, 1 };
 }
 
-QMetalRenderBuffer::QMetalRenderBuffer(QRhiImplementation *rhi, Type type, const QSize &pixelSize,
-                                       int sampleCount, QRhiRenderBuffer::Flags flags)
-    : QRhiRenderBuffer(rhi, type, pixelSize, sampleCount, flags),
-      d(new QMetalRenderBufferData)
-{
-}
-
-QMetalRenderBuffer::~QMetalRenderBuffer()
-{
-    release();
-    delete d;
-}
-
-void QMetalRenderBuffer::release()
-{
-    if (!d->tex)
-        return;
-
-    QRhiMetalData::DeferredReleaseEntry e;
-    e.type = QRhiMetalData::DeferredReleaseEntry::RenderBuffer;
-    e.lastActiveFrameSlot = lastActiveFrameSlot;
-
-    e.renderbuffer.texture = d->tex;
-    d->tex = nil;
-
-    QRHI_RES_RHI(QRhiMetal);
-    rhiD->d->releaseQueue.append(e);
-    QRHI_PROF;
-    QRHI_PROF_F(releaseRenderBuffer(this));
-    rhiD->unregisterResource(this);
-}
-
-bool QMetalRenderBuffer::build()
-{
-    if (d->tex)
-        release();
-
-    if (m_pixelSize.isEmpty())
-        return false;
-
-    QRHI_RES_RHI(QRhiMetal);
-    samples = rhiD->effectiveSampleCount(m_sampleCount);
-
-    MTLTextureDescriptor *desc = [[MTLTextureDescriptor alloc] init];
-    desc.textureType = samples > 1 ? MTLTextureType2DMultisample : MTLTextureType2D;
-    desc.width = NSUInteger(m_pixelSize.width());
-    desc.height = NSUInteger(m_pixelSize.height());
-    if (samples > 1)
-        desc.sampleCount = NSUInteger(samples);
-    desc.resourceOptions = MTLResourceStorageModePrivate;
-    desc.usage = MTLTextureUsageRenderTarget;
-
-    bool transientBacking = false;
-    switch (m_type) {
-    case DepthStencil:
-#ifdef Q_OS_MACOS
-        desc.storageMode = MTLStorageModePrivate;
-        d->format = rhiD->d->dev.depth24Stencil8PixelFormatSupported
-                ? MTLPixelFormatDepth24Unorm_Stencil8 : MTLPixelFormatDepth32Float_Stencil8;
-#else
-        desc.storageMode = MTLStorageModeMemoryless;
-        transientBacking = true;
-        d->format = MTLPixelFormatDepth32Float_Stencil8;
-#endif
-        desc.pixelFormat = d->format;
-        break;
-    case Color:
-        desc.storageMode = MTLStorageModePrivate;
-        d->format = MTLPixelFormatRGBA8Unorm;
-        desc.pixelFormat = d->format;
-        break;
-    default:
-        Q_UNREACHABLE();
-        break;
-    }
-
-    d->tex = [rhiD->d->dev newTextureWithDescriptor: desc];
-    [desc release];
-
-    if (!m_objectName.isEmpty())
-        d->tex.label = [NSString stringWithUTF8String: m_objectName.constData()];
-
-    QRHI_PROF;
-    QRHI_PROF_F(newRenderBuffer(this, transientBacking, false, samples));
-
-    lastActiveFrameSlot = -1;
-    generation += 1;
-    rhiD->registerResource(this);
-    return true;
-}
-
-QRhiTexture::Format QMetalRenderBuffer::backingFormat() const
-{
-    return m_type == Color ? QRhiTexture::RGBA8 : QRhiTexture::UnknownFormat;
-}
-
-QMetalTexture::QMetalTexture(QRhiImplementation *rhi, Format format, const QSize &pixelSize,
-                             int sampleCount, Flags flags)
-    : QRhiTexture(rhi, format, pixelSize, sampleCount, flags),
-      d(new QMetalTextureData(this))
-{
-    for (int i = 0; i < QMTL_FRAMES_IN_FLIGHT; ++i)
-        d->stagingBuf[i] = nil;
-
-    for (int i = 0; i < QRhi::MAX_LEVELS; ++i)
-        d->perLevelViews[i] = nil;
-}
-
-QMetalTexture::~QMetalTexture()
-{
-    release();
-    delete d;
-}
-
-void QMetalTexture::release()
-{
-    if (!d->tex)
-        return;
-
-    QRhiMetalData::DeferredReleaseEntry e;
-    e.type = QRhiMetalData::DeferredReleaseEntry::Texture;
-    e.lastActiveFrameSlot = lastActiveFrameSlot;
-
-    e.texture.texture = d->owns ? d->tex : nil;
-    d->tex = nil;
-
-    for (int i = 0; i < QMTL_FRAMES_IN_FLIGHT; ++i) {
-        e.texture.stagingBuffers[i] = d->stagingBuf[i];
-        d->stagingBuf[i] = nil;
-    }
-
-    for (int i = 0; i < QRhi::MAX_LEVELS; ++i) {
-        e.texture.views[i] = d->perLevelViews[i];
-        d->perLevelViews[i] = nil;
-    }
-
-    QRHI_RES_RHI(QRhiMetal);
-    rhiD->d->releaseQueue.append(e);
-    QRHI_PROF;
-    QRHI_PROF_F(releaseTexture(this));
-    rhiD->unregisterResource(this);
-}
-
 static inline MTLPixelFormat toMetalTextureFormat(QRhiTexture::Format format, QRhiTexture::Flags flags)
 {
     const bool srgb = flags.testFlag(QRhiTexture::sRGB);
@@ -2507,6 +2365,156 @@ static inline MTLPixelFormat toMetalTextureFormat(QRhiTexture::Format format, QR
     }
 }
 
+QMetalRenderBuffer::QMetalRenderBuffer(QRhiImplementation *rhi, Type type, const QSize &pixelSize,
+                                       int sampleCount, QRhiRenderBuffer::Flags flags,
+                                       QRhiTexture::Format backingFormatHint)
+    : QRhiRenderBuffer(rhi, type, pixelSize, sampleCount, flags, backingFormatHint),
+      d(new QMetalRenderBufferData)
+{
+}
+
+QMetalRenderBuffer::~QMetalRenderBuffer()
+{
+    release();
+    delete d;
+}
+
+void QMetalRenderBuffer::release()
+{
+    if (!d->tex)
+        return;
+
+    QRhiMetalData::DeferredReleaseEntry e;
+    e.type = QRhiMetalData::DeferredReleaseEntry::RenderBuffer;
+    e.lastActiveFrameSlot = lastActiveFrameSlot;
+
+    e.renderbuffer.texture = d->tex;
+    d->tex = nil;
+
+    QRHI_RES_RHI(QRhiMetal);
+    rhiD->d->releaseQueue.append(e);
+    QRHI_PROF;
+    QRHI_PROF_F(releaseRenderBuffer(this));
+    rhiD->unregisterResource(this);
+}
+
+bool QMetalRenderBuffer::build()
+{
+    if (d->tex)
+        release();
+
+    if (m_pixelSize.isEmpty())
+        return false;
+
+    QRHI_RES_RHI(QRhiMetal);
+    samples = rhiD->effectiveSampleCount(m_sampleCount);
+
+    MTLTextureDescriptor *desc = [[MTLTextureDescriptor alloc] init];
+    desc.textureType = samples > 1 ? MTLTextureType2DMultisample : MTLTextureType2D;
+    desc.width = NSUInteger(m_pixelSize.width());
+    desc.height = NSUInteger(m_pixelSize.height());
+    if (samples > 1)
+        desc.sampleCount = NSUInteger(samples);
+    desc.resourceOptions = MTLResourceStorageModePrivate;
+    desc.usage = MTLTextureUsageRenderTarget;
+
+    bool transientBacking = false;
+    switch (m_type) {
+    case DepthStencil:
+#ifdef Q_OS_MACOS
+        desc.storageMode = MTLStorageModePrivate;
+        d->format = rhiD->d->dev.depth24Stencil8PixelFormatSupported
+                ? MTLPixelFormatDepth24Unorm_Stencil8 : MTLPixelFormatDepth32Float_Stencil8;
+#else
+        desc.storageMode = MTLStorageModeMemoryless;
+        transientBacking = true;
+        d->format = MTLPixelFormatDepth32Float_Stencil8;
+#endif
+        desc.pixelFormat = d->format;
+        break;
+    case Color:
+        desc.storageMode = MTLStorageModePrivate;
+        if (m_backingFormatHint != QRhiTexture::UnknownFormat)
+            d->format = toMetalTextureFormat(m_backingFormatHint, {});
+        else
+            d->format = MTLPixelFormatRGBA8Unorm;
+        desc.pixelFormat = d->format;
+        break;
+    default:
+        Q_UNREACHABLE();
+        break;
+    }
+
+    d->tex = [rhiD->d->dev newTextureWithDescriptor: desc];
+    [desc release];
+
+    if (!m_objectName.isEmpty())
+        d->tex.label = [NSString stringWithUTF8String: m_objectName.constData()];
+
+    QRHI_PROF;
+    QRHI_PROF_F(newRenderBuffer(this, transientBacking, false, samples));
+
+    lastActiveFrameSlot = -1;
+    generation += 1;
+    rhiD->registerResource(this);
+    return true;
+}
+
+QRhiTexture::Format QMetalRenderBuffer::backingFormat() const
+{
+    if (m_backingFormatHint != QRhiTexture::UnknownFormat)
+        return m_backingFormatHint;
+    else
+        return m_type == Color ? QRhiTexture::RGBA8 : QRhiTexture::UnknownFormat;
+}
+
+QMetalTexture::QMetalTexture(QRhiImplementation *rhi, Format format, const QSize &pixelSize,
+                             int sampleCount, Flags flags)
+    : QRhiTexture(rhi, format, pixelSize, sampleCount, flags),
+      d(new QMetalTextureData(this))
+{
+    for (int i = 0; i < QMTL_FRAMES_IN_FLIGHT; ++i)
+        d->stagingBuf[i] = nil;
+
+    for (int i = 0; i < QRhi::MAX_LEVELS; ++i)
+        d->perLevelViews[i] = nil;
+}
+
+QMetalTexture::~QMetalTexture()
+{
+    release();
+    delete d;
+}
+
+void QMetalTexture::release()
+{
+    if (!d->tex)
+        return;
+
+    QRhiMetalData::DeferredReleaseEntry e;
+    e.type = QRhiMetalData::DeferredReleaseEntry::Texture;
+    e.lastActiveFrameSlot = lastActiveFrameSlot;
+
+    e.texture.texture = d->owns ? d->tex : nil;
+    d->tex = nil;
+
+    for (int i = 0; i < QMTL_FRAMES_IN_FLIGHT; ++i) {
+        e.texture.stagingBuffers[i] = d->stagingBuf[i];
+        d->stagingBuf[i] = nil;
+    }
+
+    for (int i = 0; i < QRhi::MAX_LEVELS; ++i) {
+        e.texture.views[i] = d->perLevelViews[i];
+        d->perLevelViews[i] = nil;
+    }
+
+    QRHI_RES_RHI(QRhiMetal);
+    rhiD->d->releaseQueue.append(e);
+    QRHI_PROF;
+    QRHI_PROF_F(releaseTexture(this));
+    rhiD->unregisterResource(this);
+}
+
 bool QMetalTexture::prepareBuild(QSize *adjustedSize)
 {
     if (d->tex)

src/gui/rhi/qrhimetal_p_p.h

@@ -79,7 +79,8 @@ struct QMetalRenderBufferData;
 struct QMetalRenderBuffer : public QRhiRenderBuffer
 {
     QMetalRenderBuffer(QRhiImplementation *rhi, Type type, const QSize &pixelSize,
-                       int sampleCount, QRhiRenderBuffer::Flags flags);
+                       int sampleCount, QRhiRenderBuffer::Flags flags,
+                       QRhiTexture::Format backingFormatHint);
     ~QMetalRenderBuffer();
     void release() override;
     bool build() override;
@@ -349,7 +350,8 @@ public:
     QRhiRenderBuffer *createRenderBuffer(QRhiRenderBuffer::Type type,
                                          const QSize &pixelSize,
                                          int sampleCount,
-                                         QRhiRenderBuffer::Flags flags) override;
+                                         QRhiRenderBuffer::Flags flags,
+                                         QRhiTexture::Format backingFormatHint) override;
     QRhiTexture *createTexture(QRhiTexture::Format format,
                                const QSize &pixelSize,
                                int sampleCount,

src/gui/rhi/qrhinull.cpp

@@ -182,9 +182,10 @@ bool QRhiNull::isDeviceLost() const
 }
 
 QRhiRenderBuffer *QRhiNull::createRenderBuffer(QRhiRenderBuffer::Type type, const QSize &pixelSize,
-                                               int sampleCount, QRhiRenderBuffer::Flags flags)
+                                               int sampleCount, QRhiRenderBuffer::Flags flags,
+                                               QRhiTexture::Format backingFormatHint)
 {
-    return new QNullRenderBuffer(this, type, pixelSize, sampleCount, flags);
+    return new QNullRenderBuffer(this, type, pixelSize, sampleCount, flags, backingFormatHint);
 }
 
 QRhiTexture *QRhiNull::createTexture(QRhiTexture::Format format, const QSize &pixelSize,
@@ -564,8 +565,9 @@ bool QNullBuffer::build()
 }
 
 QNullRenderBuffer::QNullRenderBuffer(QRhiImplementation *rhi, Type type, const QSize &pixelSize,
-                                     int sampleCount, QRhiRenderBuffer::Flags flags)
+                                     int sampleCount, QRhiRenderBuffer::Flags flags,
-    : QRhiRenderBuffer(rhi, type, pixelSize, sampleCount, flags)
+                                     QRhiTexture::Format backingFormatHint)
+    : QRhiRenderBuffer(rhi, type, pixelSize, sampleCount, flags, backingFormatHint)
 {
 }
 

src/gui/rhi/qrhinull_p_p.h

@@ -66,7 +66,8 @@ struct QNullBuffer : public QRhiBuffer
 struct QNullRenderBuffer : public QRhiRenderBuffer
 {
     QNullRenderBuffer(QRhiImplementation *rhi, Type type, const QSize &pixelSize,
-                       int sampleCount, QRhiRenderBuffer::Flags flags);
+                      int sampleCount, QRhiRenderBuffer::Flags flags,
+                      QRhiTexture::Format backingFormatHint);
     ~QNullRenderBuffer();
     void release() override;
     bool build() override;
@@ -207,7 +208,8 @@ public:
     QRhiRenderBuffer *createRenderBuffer(QRhiRenderBuffer::Type type,
                                          const QSize &pixelSize,
                                          int sampleCount,
-                                         QRhiRenderBuffer::Flags flags) override;
+                                         QRhiRenderBuffer::Flags flags,
+                                         QRhiTexture::Format backingFormatHint) override;
     QRhiTexture *createTexture(QRhiTexture::Format format,
                                const QSize &pixelSize,
                                int sampleCount,

src/gui/rhi/qrhivulkan.cpp

@@ -4084,9 +4084,10 @@ bool QRhiVulkan::isDeviceLost() const
 }
 
 QRhiRenderBuffer *QRhiVulkan::createRenderBuffer(QRhiRenderBuffer::Type type, const QSize &pixelSize,
-                                                 int sampleCount, QRhiRenderBuffer::Flags flags)
+                                                 int sampleCount, QRhiRenderBuffer::Flags flags,
+                                                 QRhiTexture::Format backingFormatHint)
 {
-    return new QVkRenderBuffer(this, type, pixelSize, sampleCount, flags);
+    return new QVkRenderBuffer(this, type, pixelSize, sampleCount, flags, backingFormatHint);
 }
 
 QRhiTexture *QRhiVulkan::createTexture(QRhiTexture::Format format, const QSize &pixelSize,
@@ -5241,8 +5242,9 @@ QRhiBuffer::NativeBuffer QVkBuffer::nativeBuffer()
 }
 
 QVkRenderBuffer::QVkRenderBuffer(QRhiImplementation *rhi, Type type, const QSize &pixelSize,
-                                 int sampleCount, Flags flags)
+                                 int sampleCount, Flags flags,
-    : QRhiRenderBuffer(rhi, type, pixelSize, sampleCount, flags)
+                                 QRhiTexture::Format backingFormatHint)
+    : QRhiRenderBuffer(rhi, type, pixelSize, sampleCount, flags, backingFormatHint)
 {
 }
 
@@ -5300,7 +5302,7 @@ bool QVkRenderBuffer::build()
     case QRhiRenderBuffer::Color:
     {
         if (!backingTexture) {
-            backingTexture = QRHI_RES(QVkTexture, rhiD->createTexture(QRhiTexture::RGBA8,
+            backingTexture = QRHI_RES(QVkTexture, rhiD->createTexture(backingFormat(),
                                                                       m_pixelSize,
                                                                       m_sampleCount,
                                                                       QRhiTexture::RenderTarget | QRhiTexture::UsedAsTransferSource));
@@ -5344,7 +5346,10 @@ bool QVkRenderBuffer::build()
 
 QRhiTexture::Format QVkRenderBuffer::backingFormat() const
 {
-    return m_type == Color ? QRhiTexture::RGBA8 : QRhiTexture::UnknownFormat;
+    if (m_backingFormatHint != QRhiTexture::UnknownFormat)
+        return m_backingFormatHint;
+    else
+        return m_type == Color ? QRhiTexture::RGBA8 : QRhiTexture::UnknownFormat;
 }
 
 QVkTexture::QVkTexture(QRhiImplementation *rhi, Format format, const QSize &pixelSize,

src/gui/rhi/qrhivulkan_p_p.h

@@ -98,7 +98,8 @@ struct QVkTexture;
 struct QVkRenderBuffer : public QRhiRenderBuffer
 {
     QVkRenderBuffer(QRhiImplementation *rhi, Type type, const QSize &pixelSize,
-                    int sampleCount, Flags flags);
+                    int sampleCount, Flags flags,
+                    QRhiTexture::Format backingFormatHint);
     ~QVkRenderBuffer();
     void release() override;
     bool build() override;
@@ -658,7 +659,8 @@ public:
     QRhiRenderBuffer *createRenderBuffer(QRhiRenderBuffer::Type type,
                                          const QSize &pixelSize,
                                          int sampleCount,
-                                         QRhiRenderBuffer::Flags flags) override;
+                                         QRhiRenderBuffer::Flags flags,
+                                         QRhiTexture::Format backingFormatHint) override;
     QRhiTexture *createTexture(QRhiTexture::Format format,
                                const QSize &pixelSize,
                                int sampleCount,