11 files changed, 162 insertions, 2 deletions

diff --git a/src/gui/rhi/qrhi.cpp b/src/gui/rhi/qrhi.cpp
index 952183f55e..70525689e9 100644
--- a/src/gui/rhi/qrhi.cpp
+++ b/src/gui/rhi/qrhi.cpp
@@ -330,9 +330,22 @@ Q_LOGGING_CATEGORY(QRHI_LOG_INFO, "qt.rhi.general")
         ubuf->setSize(512);
         ubuf->create(); // same as ubuf->destroy(); ubuf->create();
 
-        // that's it, srb needs no changes whatsoever
+        // That's it, srb needs no changes whatsoever, any references in it to
+        // ubuf stay valid. When it comes to internal details, such as that
+        // ubuf may now be backed by a completely different native buffer
+        // resource, that is is recognized and handled automatically by the
+        // next setShaderResources().
     \endcode
 
+    QRhiTextureRenderTarget offers the same contract: calling
+    QRhiCommandBuffer::beginPass() is safe even when one of the render target's
+    associated textures or renderbuffers has been rebuilt (by calling \c
+    create() on it) since the creation of the render target object. This allows
+    the application to resize a texture by setting a new pixel size on the
+    QRhiTexture and calling create(), thus creating a whole new native texture
+    resource underneath, without having to update the QRhiTextureRenderTarget
+    as that will be done implicitly in beginPass().
+
     \section3 Pooled objects
 
     In addition to resources, there are pooled objects as well, such as,
@@ -5669,6 +5682,25 @@ void QRhiCommandBuffer::resourceUpdate(QRhiResourceUpdateBatch *resourceUpdates)
     called inside a pass. Also, with the exception of setGraphicsPipeline(),
     they expect to have a pipeline set already on the command buffer.
     Unspecified issues may arise otherwise, depending on the backend.
+
+    If \a rt is a QRhiTextureRenderTarget, beginPass() performs a check to see
+    if the texture and renderbuffer objects referenced from the render target
+    are up-to-date. This is similar to what setShaderResources() does for
+    QRhiShaderResourceBindings. If any of the attachments had been rebuilt
+    since QRhiTextureRenderTarget::create(), an implicit call to create() is
+    made on \a rt. Therefore, if \a rt has a QRhiTexture color attachment \c
+    texture, and one needs to make the texture a different size, the following
+    is then valid:
+    \badcode
+      rt = rhi->newTextureRenderTarget({ { texture } });
+      rt->create();
+      ...
+      texture->setPixelSize(new_size);
+      texture->create();
+      cb->beginPass(rt, ...); // this is ok, no explicit rt->create() is required before
+    \endcode
+
+    \sa endPass()
  */
 void QRhiCommandBuffer::beginPass(QRhiRenderTarget *rt,
                                   const QColor &colorClearValue,
@@ -5684,6 +5716,8 @@ void QRhiCommandBuffer::beginPass(QRhiRenderTarget *rt,
 
     \a resourceUpdates, when not null, specifies a resource update batch that
     is to be committed and then released.
+
+    \sa beginPass()
  */
 void QRhiCommandBuffer::endPass(QRhiResourceUpdateBatch *resourceUpdates)
 {
diff --git a/src/gui/rhi/qrhi_p_p.h b/src/gui/rhi/qrhi_p_p.h
index 7a3f94846d..9e8a3a846f 100644
--- a/src/gui/rhi/qrhi_p_p.h
+++ b/src/gui/rhi/qrhi_p_p.h
@@ -706,6 +706,83 @@ private:
     int p = 0;
 };
 
+struct QRhiRenderTargetAttachmentTracker
+{
+    struct ResId { quint64 id; uint generation; };
+    using ResIdList = QVarLengthArray<ResId, 8 * 2 + 1>; // color, resolve, ds
+
+    template<typename TexType, typename RenderBufferType>
+    static void updateResIdList(const QRhiTextureRenderTargetDescription &desc, ResIdList *dst);
+
+    template<typename TexType, typename RenderBufferType>
+    static bool isUpToDate(const QRhiTextureRenderTargetDescription &desc, const ResIdList &currentResIdList);
+};
+
+inline bool operator==(const QRhiRenderTargetAttachmentTracker::ResId &a, const QRhiRenderTargetAttachmentTracker::ResId &b)
+{
+    return a.id == b.id && a.generation == b.generation;
+}
+
+inline bool operator!=(const QRhiRenderTargetAttachmentTracker::ResId &a, const QRhiRenderTargetAttachmentTracker::ResId &b)
+{
+    return !(a == b);
+}
+
+template<typename TexType, typename RenderBufferType>
+void QRhiRenderTargetAttachmentTracker::updateResIdList(const QRhiTextureRenderTargetDescription &desc, ResIdList *dst)
+{
+    const quintptr colorAttCount = desc.cendColorAttachments() - desc.cbeginColorAttachments();
+    const bool hasDepthStencil = desc.depthStencilBuffer() || desc.depthTexture();
+    dst->resize(colorAttCount * 2 + (hasDepthStencil ? 1 : 0));
+    int n = 0;
+    for (auto it = desc.cbeginColorAttachments(), itEnd = desc.cendColorAttachments(); it != itEnd; ++it, ++n) {
+        const QRhiColorAttachment &colorAtt(*it);
+        if (colorAtt.texture()) {
+            TexType *texD = QRHI_RES(TexType, colorAtt.texture());
+            (*dst)[n] = { texD->globalResourceId(), texD->generation };
+        } else if (colorAtt.renderBuffer()) {
+            RenderBufferType *rbD = QRHI_RES(RenderBufferType, colorAtt.renderBuffer());
+            (*dst)[n] = { rbD->globalResourceId(), rbD->generation };
+        } else {
+            (*dst)[n] = { 0, 0 };
+        }
+        ++n;
+        if (colorAtt.resolveTexture()) {
+            TexType *texD = QRHI_RES(TexType, colorAtt.resolveTexture());
+            (*dst)[n] = { texD->globalResourceId(), texD->generation };
+        } else {
+            (*dst)[n] = { 0, 0 };
+        }
+    }
+    if (hasDepthStencil) {
+        if (desc.depthTexture()) {
+            TexType *depthTexD = QRHI_RES(TexType, desc.depthTexture());
+            (*dst)[n] = { depthTexD->globalResourceId(), depthTexD->generation };
+        } else if (desc.depthStencilBuffer()) {
+            RenderBufferType *depthRbD = QRHI_RES(RenderBufferType, desc.depthStencilBuffer());
+            (*dst)[n] = { depthRbD->globalResourceId(), depthRbD->generation };
+        } else {
+            (*dst)[n] = { 0, 0 };
+        }
+    }
+}
+
+template<typename TexType, typename RenderBufferType>
+bool QRhiRenderTargetAttachmentTracker::isUpToDate(const QRhiTextureRenderTargetDescription &desc, const ResIdList &currentResIdList)
+{
+    // Just as setShaderResources() recognizes if an srb's referenced
+    // resources have been rebuilt (got a create() since the srb's
+    // create()), we should do the same for the textures and renderbuffers
+    // referenced from the rendertarget. It is not uncommon that a texture
+    // or ds buffer gets resized due to following a window size in some
+    // form, which involves a create() on them. It is then nice if the
+    // render target auto-rebuilds in beginPass().
+
+    ResIdList resIdList;
+    updateResIdList<TexType, RenderBufferType>(desc, &resIdList);
+    return resIdList == currentResIdList;
+}
+
 QT_END_NAMESPACE
 
 #endif
diff --git a/src/gui/rhi/qrhid3d11.cpp b/src/gui/rhi/qrhid3d11.cpp
index f6076bc800..a8fd9a686f 100644
--- a/src/gui/rhi/qrhid3d11.cpp
+++ b/src/gui/rhi/qrhid3d11.cpp
@@ -1762,6 +1762,8 @@ void QRhiD3D11::beginPass(QRhiCommandBuffer *cb,
         QD3D11TextureRenderTarget *rtTex = QRHI_RES(QD3D11TextureRenderTarget, rt);
         wantsColorClear = !rtTex->m_flags.testFlag(QRhiTextureRenderTarget::PreserveColorContents);
         wantsDsClear = !rtTex->m_flags.testFlag(QRhiTextureRenderTarget::PreserveDepthStencilContents);
+        if (!QRhiRenderTargetAttachmentTracker::isUpToDate<QD3D11Texture, QD3D11RenderBuffer>(rtTex->description(), rtD->currentResIdList))
+            rtTex->create();
     }
 
     cbD->commands.get().cmd = QD3D11CommandBuffer::Command::ResetShaderResources;
@@ -2898,6 +2900,7 @@ bool QD3D11RenderBuffer::create()
     QRHI_PROF;
     QRHI_PROF_F(newRenderBuffer(this, false, false, int(sampleDesc.Count)));
 
+    generation += 1;
     rhiD->registerResource(this);
     return true;
 }
@@ -3609,6 +3612,8 @@ bool QD3D11TextureRenderTarget::create()
     d.dsv = dsv;
     d.rp = QRHI_RES(QD3D11RenderPassDescriptor, m_renderPassDesc);
 
+    QRhiRenderTargetAttachmentTracker::updateResIdList<QD3D11Texture, QD3D11RenderBuffer>(m_desc, &d.currentResIdList);
+
     rhiD->registerResource(this);
     return true;
 }
diff --git a/src/gui/rhi/qrhid3d11_p_p.h b/src/gui/rhi/qrhid3d11_p_p.h
index 3a333fe8a7..70c7ad969b 100644
--- a/src/gui/rhi/qrhid3d11_p_p.h
+++ b/src/gui/rhi/qrhid3d11_p_p.h
@@ -96,6 +96,7 @@ struct QD3D11RenderBuffer : public QRhiRenderBuffer
     ID3D11RenderTargetView *rtv = nullptr;
     DXGI_FORMAT dxgiFormat;
     DXGI_SAMPLE_DESC sampleDesc;
+    uint generation = 0;
     friend class QRhiD3D11;
 };
 
@@ -172,6 +173,8 @@ struct QD3D11RenderTargetData
     static const int MAX_COLOR_ATTACHMENTS = 8;
     ID3D11RenderTargetView *rtv[MAX_COLOR_ATTACHMENTS];
     ID3D11DepthStencilView *dsv = nullptr;
+
+    QRhiRenderTargetAttachmentTracker::ResIdList currentResIdList;
 };
 
 struct QD3D11ReferenceRenderTarget : public QRhiRenderTarget
diff --git a/src/gui/rhi/qrhigles2.cpp b/src/gui/rhi/qrhigles2.cpp
index f0b97ce36a..67d08d3042 100644
--- a/src/gui/rhi/qrhigles2.cpp
+++ b/src/gui/rhi/qrhigles2.cpp
@@ -3793,6 +3793,12 @@ void QRhiGles2::beginPass(QRhiCommandBuffer *cb,
     // glMemoryBarrier() calls based on that tracker when submitted.
     enqueueBarriersForPass(cbD);
 
+    if (rt->resourceType() == QRhiRenderTarget::TextureRenderTarget) {
+        QGles2TextureRenderTarget *rtTex = QRHI_RES(QGles2TextureRenderTarget, rt);
+        if (!QRhiRenderTargetAttachmentTracker::isUpToDate<QGles2Texture, QGles2RenderBuffer>(rtTex->description(), rtTex->d.currentResIdList))
+            rtTex->create();
+    }
+
     bool wantsColorClear, wantsDsClear;
     QGles2RenderTargetData *rtD = enqueueBindFramebuffer(rt, cbD, &wantsColorClear, &wantsDsClear);
 
@@ -4626,6 +4632,7 @@ bool QGles2RenderBuffer::create()
     }
 
     owns = true;
+    generation += 1;
     rhiD->registerResource(this);
     return true;
 }
@@ -4653,6 +4660,7 @@ bool QGles2RenderBuffer::createFrom(NativeRenderBuffer src)
     QRHI_PROF_F(newRenderBuffer(this, false, false, samples));
 
     owns = false;
+    generation += 1;
     rhiD->registerResource(this);
     return true;
 }
@@ -5114,6 +5122,8 @@ bool QGles2TextureRenderTarget::create()
         return false;
     }
 
+    QRhiRenderTargetAttachmentTracker::updateResIdList<QGles2Texture, QGles2RenderBuffer>(m_desc, &d.currentResIdList);
+
     rhiD->registerResource(this);
     return true;
 }
diff --git a/src/gui/rhi/qrhigles2_p_p.h b/src/gui/rhi/qrhigles2_p_p.h
index 6ee6af8fc5..c0f3883002 100644
--- a/src/gui/rhi/qrhigles2_p_p.h
+++ b/src/gui/rhi/qrhigles2_p_p.h
@@ -108,6 +108,7 @@ struct QGles2RenderBuffer : public QRhiRenderBuffer
     GLuint stencilRenderbuffer = 0; // when packed depth-stencil not supported
     int samples;
     bool owns = true;
+    uint generation = 0;
     friend class QRhiGles2;
 };
 
@@ -213,6 +214,7 @@ struct QGles2RenderTargetData
     int colorAttCount = 0;
     int dsAttCount = 0;
     bool srgbUpdateAndBlend = false;
+    QRhiRenderTargetAttachmentTracker::ResIdList currentResIdList;
 };
 
 struct QGles2ReferenceRenderTarget : public QRhiRenderTarget
diff --git a/src/gui/rhi/qrhimetal.mm b/src/gui/rhi/qrhimetal.mm
index 5219b5c71d..626eac433b 100644
--- a/src/gui/rhi/qrhimetal.mm
+++ b/src/gui/rhi/qrhimetal.mm
@@ -296,6 +296,8 @@ struct QMetalRenderTargetData
         bool hasStencil = false;
         bool depthNeedsStore = false;
     } fb;
+
+    QRhiRenderTargetAttachmentTracker::ResIdList currentResIdList;
 };
 
 struct QMetalGraphicsPipelineData
@@ -2030,6 +2032,8 @@ void QRhiMetal::beginPass(QRhiCommandBuffer *cb,
     {
         QMetalTextureRenderTarget *rtTex = QRHI_RES(QMetalTextureRenderTarget, rt);
         rtD = rtTex->d;
+        if (!QRhiRenderTargetAttachmentTracker::isUpToDate<QMetalTexture, QMetalRenderBuffer>(rtTex->description(), rtD->currentResIdList))
+            rtTex->create();
         cbD->d->currentPassRpDesc = d->createDefaultRenderPass(rtD->dsAttCount, colorClearValue, depthStencilClearValue, rtD->colorAttCount);
         if (rtTex->m_flags.testFlag(QRhiTextureRenderTarget::PreserveColorContents)) {
             for (uint i = 0; i < uint(rtD->colorAttCount); ++i)
@@ -3181,6 +3185,8 @@ bool QMetalTextureRenderTarget::create()
         d->dsAttCount = 0;
     }
 
+    QRhiRenderTargetAttachmentTracker::updateResIdList<QMetalTexture, QMetalRenderBuffer>(m_desc, &d->currentResIdList);
+
     return true;
 }
 
diff --git a/src/gui/rhi/qrhinull.cpp b/src/gui/rhi/qrhinull.cpp
index b23af75bd9..6e85e02cc2 100644
--- a/src/gui/rhi/qrhinull.cpp
+++ b/src/gui/rhi/qrhinull.cpp
@@ -553,12 +553,18 @@ void QRhiNull::beginPass(QRhiCommandBuffer *cb,
                          QRhiResourceUpdateBatch *resourceUpdates,
                          QRhiCommandBuffer::BeginPassFlags flags)
 {
-    Q_UNUSED(rt);
     Q_UNUSED(colorClearValue);
     Q_UNUSED(depthStencilClearValue);
     Q_UNUSED(flags);
+
     if (resourceUpdates)
         resourceUpdate(cb, resourceUpdates);
+
+    if (rt->resourceType() == QRhiRenderTarget::TextureRenderTarget) {
+        QNullTextureRenderTarget *rtTex = QRHI_RES(QNullTextureRenderTarget, rt);
+        if (!QRhiRenderTargetAttachmentTracker::isUpToDate<QNullTexture, QNullRenderBuffer>(rtTex->description(), rtTex->d.currentResIdList))
+            rtTex->create();
+    }
 }
 
 void QRhiNull::endPass(QRhiCommandBuffer *cb, QRhiResourceUpdateBatch *resourceUpdates)
@@ -660,6 +666,7 @@ bool QNullRenderBuffer::create()
         destroy();
 
     valid = true;
+    generation += 1;
 
     QRHI_PROF;
     QRHI_PROF_F(newRenderBuffer(this, false, false, 1));
@@ -726,6 +733,8 @@ bool QNullTexture::create()
         }
     }
 
+    generation += 1;
+
     QRHI_PROF;
     QRHI_PROF_F(newTexture(this, true, mipLevelCount, layerCount, 1));
     rhiD->registerResource(this);
@@ -748,6 +757,8 @@ bool QNullTexture::createFrom(QRhiTexture::NativeTexture src)
     QSize size = m_pixelSize.isEmpty() ? QSize(1, 1) : m_pixelSize;
     const int mipLevelCount = hasMipMaps ? rhiD->q->mipLevelsForSize(size) : 1;
 
+    generation += 1;
+
     QRHI_PROF;
     QRHI_PROF_F(newTexture(this, false, mipLevelCount, isCube ? 6 : (isArray ? m_arraySize : 1), 1));
     rhiD->registerResource(this);
@@ -871,6 +882,7 @@ bool QNullTextureRenderTarget::create()
     } else if (m_desc.depthTexture()) {
         d.pixelSize = m_desc.depthTexture()->pixelSize();
     }
+    QRhiRenderTargetAttachmentTracker::updateResIdList<QNullTexture, QNullRenderBuffer>(m_desc, &d.currentResIdList);
     return true;
 }
 
diff --git a/src/gui/rhi/qrhinull_p_p.h b/src/gui/rhi/qrhinull_p_p.h
index 4d3c508044..217ec8ef39 100644
--- a/src/gui/rhi/qrhinull_p_p.h
+++ b/src/gui/rhi/qrhinull_p_p.h
@@ -78,6 +78,7 @@ struct QNullRenderBuffer : public QRhiRenderBuffer
     QRhiTexture::Format backingFormat() const override;
 
     bool valid = false;
+    uint generation = 0;
 };
 
 struct QNullTexture : public QRhiTexture
@@ -91,6 +92,7 @@ struct QNullTexture : public QRhiTexture
 
     bool valid = false;
     QVarLengthArray<std::array<QImage, QRhi::MAX_MIP_LEVELS>, 6> image;
+    uint generation = 0;
 };
 
 struct QNullSampler : public QRhiSampler
@@ -119,6 +121,7 @@ struct QNullRenderTargetData
     QNullRenderPassDescriptor *rp = nullptr;
     QSize pixelSize;
     float dpr = 1;
+    QRhiRenderTargetAttachmentTracker::ResIdList currentResIdList;
 };
 
 struct QNullReferenceRenderTarget : public QRhiRenderTarget
diff --git a/src/gui/rhi/qrhivulkan.cpp b/src/gui/rhi/qrhivulkan.cpp
index 03f3fb4ad8..e23900069c 100644
--- a/src/gui/rhi/qrhivulkan.cpp
+++ b/src/gui/rhi/qrhivulkan.cpp
@@ -2175,6 +2175,9 @@ static inline QRhiPassResourceTracker::UsageState toPassTrackerUsageState(const
 
 void QRhiVulkan::activateTextureRenderTarget(QVkCommandBuffer *cbD, QVkTextureRenderTarget *rtD)
 {
+    if (!QRhiRenderTargetAttachmentTracker::isUpToDate<QVkTexture, QVkRenderBuffer>(rtD->description(), rtD->d.currentResIdList))
+        rtD->create();
+
     rtD->lastActiveFrameSlot = currentFrameSlot;
     rtD->d.rp->lastActiveFrameSlot = currentFrameSlot;
     QRhiPassResourceTracker &passResTracker(cbD->passResTrackers[cbD->currentPassResTrackerIndex]);
@@ -5759,6 +5762,7 @@ bool QVkRenderBuffer::create()
     }
 
     lastActiveFrameSlot = -1;
+    generation += 1;
     rhiD->registerResource(this);
     return true;
 }
@@ -6572,6 +6576,8 @@ bool QVkTextureRenderTarget::create()
         return false;
     }
 
+    QRhiRenderTargetAttachmentTracker::updateResIdList<QVkTexture, QVkRenderBuffer>(m_desc, &d.currentResIdList);
+
     lastActiveFrameSlot = -1;
     rhiD->registerResource(this);
     return true;
diff --git a/src/gui/rhi/qrhivulkan_p_p.h b/src/gui/rhi/qrhivulkan_p_p.h
index 42ae9aef3b..da69a0d70d 100644
--- a/src/gui/rhi/qrhivulkan_p_p.h
+++ b/src/gui/rhi/qrhivulkan_p_p.h
@@ -123,6 +123,7 @@ struct QVkRenderBuffer : public QRhiRenderBuffer
     QVkTexture *backingTexture = nullptr;
     VkFormat vkformat;
     int lastActiveFrameSlot = -1;
+    uint generation = 0;
     friend class QRhiVulkan;
 };
 
@@ -214,6 +215,7 @@ struct QVkRenderTargetData
     int colorAttCount = 0;
     int dsAttCount = 0;
     int resolveAttCount = 0;
+    QRhiRenderTargetAttachmentTracker::ResIdList currentResIdList;
     static const int MAX_COLOR_ATTACHMENTS = 8;
 };