rhi: Make sure pixelSize() to a texture rt is always up to date

This is an issue for QQuickWindow in practice, although it is not hit
by our current tests.

Pick-to: 6.3
Change-Id: Ia73704c1af6a82b2689ce7b844d3b0eb9a17ec18
Reviewed-by: Christian Strømme <christian.stromme@qt.io>

src/gui/rhi/qrhi.cpp

@@ -2929,6 +2929,18 @@ QRhiResource::Type QRhiRenderTarget::resourceType() const
     \fn QSize QRhiRenderTarget::pixelSize() const
 
     \return the size in pixels.
+
+    Valid only after create() has been called successfully. Until then the
+    result is a default-constructed QSize.
+
+    With QRhiTextureRenderTarget the returned size is the size of the
+    associated attachments at the time of create(), in practice the size of the
+    first color attachment, or the depth/stencil buffer if there are no color
+    attachments. If the associated textures or renderbuffers are resized and
+    rebuilt afterwards, then pixelSize() performs an implicit call to create()
+    in order to rebuild the underlying data structures. This implicit check is
+    similar to what QRhiCommandBuffer::beginPass() does, and ensures that the
+    returned size is always up-to-date.
  */
 
 /*!

src/gui/rhi/qrhid3d11.cpp

@@ -3631,6 +3631,9 @@ bool QD3D11TextureRenderTarget::create()
 
 QSize QD3D11TextureRenderTarget::pixelSize() const
 {
+    if (!QRhiRenderTargetAttachmentTracker::isUpToDate<QD3D11Texture, QD3D11RenderBuffer>(m_desc, d.currentResIdList))
+        const_cast<QD3D11TextureRenderTarget *>(this)->create();
+
     return d.pixelSize;
 }
 

src/gui/rhi/qrhigles2.cpp

@@ -5317,6 +5317,9 @@ bool QGles2TextureRenderTarget::create()
 
 QSize QGles2TextureRenderTarget::pixelSize() const
 {
+    if (!QRhiRenderTargetAttachmentTracker::isUpToDate<QGles2Texture, QGles2RenderBuffer>(m_desc, d.currentResIdList))
+        const_cast<QGles2TextureRenderTarget *>(this)->create();
+
     return d.pixelSize;
 }
 

src/gui/rhi/qrhimetal.mm

@@ -3183,6 +3183,9 @@ bool QMetalTextureRenderTarget::create()
 
 QSize QMetalTextureRenderTarget::pixelSize() const
 {
+    if (!QRhiRenderTargetAttachmentTracker::isUpToDate<QMetalTexture, QMetalRenderBuffer>(m_desc, d->currentResIdList))
+        const_cast<QMetalTextureRenderTarget *>(this)->create();
+
     return d->pixelSize;
 }
 

src/gui/rhi/qrhinull.cpp

@@ -860,6 +860,9 @@ bool QNullTextureRenderTarget::create()
 
 QSize QNullTextureRenderTarget::pixelSize() const
 {
+    if (!QRhiRenderTargetAttachmentTracker::isUpToDate<QNullTexture, QNullRenderBuffer>(m_desc, d.currentResIdList))
+        const_cast<QNullTextureRenderTarget *>(this)->create();
+
     return d.pixelSize;
 }
 

src/gui/rhi/qrhivulkan.cpp

@@ -6637,6 +6637,9 @@ bool QVkTextureRenderTarget::create()
 
 QSize QVkTextureRenderTarget::pixelSize() const
 {
+    if (!QRhiRenderTargetAttachmentTracker::isUpToDate<QVkTexture, QVkRenderBuffer>(m_desc, d.currentResIdList))
+        const_cast<QVkTextureRenderTarget *>(this)->create();
+
     return d.pixelSize;
 }
 

tests/auto/gui/rhi/qrhi/tst_qrhi.cpp

@@ -3828,33 +3828,51 @@ void tst_QRhi::textureRenderTargetAutoRebuild()
     if (!rhi)
         QSKIP("QRhi could not be created, skipping testing rendering");
 
-    QScopedPointer<QRhiTexture> texture(rhi->newTexture(QRhiTexture::RGBA8, QSize(512, 512), 1, QRhiTexture::RenderTarget));
-    QVERIFY(texture->create());
-    QScopedPointer<QRhiTextureRenderTarget> rt(rhi->newTextureRenderTarget({ { texture.data() } }));
-    QScopedPointer<QRhiRenderPassDescriptor> rp(rt->newCompatibleRenderPassDescriptor());
-    rt->setRenderPassDescriptor(rp.data());
-    QVERIFY(rt->create());
+    // case 1: beginPass's implicit create()
+    {
+        QScopedPointer<QRhiTexture> texture(rhi->newTexture(QRhiTexture::RGBA8, QSize(512, 512), 1, QRhiTexture::RenderTarget));
+        QVERIFY(texture->create());
+        QScopedPointer<QRhiTextureRenderTarget> rt(rhi->newTextureRenderTarget({ { texture.data() } }));
+        QScopedPointer<QRhiRenderPassDescriptor> rp(rt->newCompatibleRenderPassDescriptor());
+        rt->setRenderPassDescriptor(rp.data());
+        QVERIFY(rt->create());
 
-    QRhiCommandBuffer *cb = nullptr;
-    QVERIFY(rhi->beginOffscreenFrame(&cb) == QRhi::FrameOpSuccess);
-    QVERIFY(cb);
-    cb->beginPass(rt.data(), Qt::red, { 1.0f, 0 });
-    cb->endPass();
-    rhi->endOffscreenFrame();
+        QRhiCommandBuffer *cb = nullptr;
+        QVERIFY(rhi->beginOffscreenFrame(&cb) == QRhi::FrameOpSuccess);
+        QVERIFY(cb);
+        cb->beginPass(rt.data(), Qt::red, { 1.0f, 0 });
+        cb->endPass();
+        rhi->endOffscreenFrame();
 
-    texture->setPixelSize(QSize(256, 256));
-    QVERIFY(texture->create());
-    QCOMPARE(texture->pixelSize(), QSize(256, 256));
-    // rt still has the old size and knows nothing about texture's underlying native texture resource possibly changing
-    QCOMPARE(rt->pixelSize(), QSize(512, 512));
+        texture->setPixelSize(QSize(256, 256));
+        QVERIFY(texture->create());
+        QCOMPARE(texture->pixelSize(), QSize(256, 256));
 
-    QVERIFY(rhi->beginOffscreenFrame(&cb) == QRhi::FrameOpSuccess);
-    QVERIFY(cb);
-    // no rt->create() but beginPass() does it implicitly for us
-    cb->beginPass(rt.data(), Qt::red, { 1.0f, 0 });
-    QCOMPARE(rt->pixelSize(), QSize(256, 256));
-    cb->endPass();
-    rhi->endOffscreenFrame();
+        QVERIFY(rhi->beginOffscreenFrame(&cb) == QRhi::FrameOpSuccess);
+        QVERIFY(cb);
+        // no rt->create() but beginPass() does it implicitly for us
+        cb->beginPass(rt.data(), Qt::red, { 1.0f, 0 });
+        QCOMPARE(rt->pixelSize(), QSize(256, 256));
+        cb->endPass();
+        rhi->endOffscreenFrame();
+    }
+
+    // case 2: pixelSize's implicit create()
+    {
+        QSize sz(512, 512);
+        QScopedPointer<QRhiTexture> texture(rhi->newTexture(QRhiTexture::RGBA8, sz, 1, QRhiTexture::RenderTarget));
+        QVERIFY(texture->create());
+        QScopedPointer<QRhiTextureRenderTarget> rt(rhi->newTextureRenderTarget({ { texture.data() } }));
+        QScopedPointer<QRhiRenderPassDescriptor> rp(rt->newCompatibleRenderPassDescriptor());
+        rt->setRenderPassDescriptor(rp.data());
+        QVERIFY(rt->create());
+        QCOMPARE(rt->pixelSize(), sz);
+
+        sz = QSize(256, 256);
+        texture->setPixelSize(sz);
+        QVERIFY(texture->create());
+        QCOMPARE(rt->pixelSize(), sz);
+    }
 }
 
 void tst_QRhi::srbLayoutCompatibility_data()