rhi: Auto-rebuild rt by tracking attachment id and generation

Unlike the shader resource binding lists that automatically recognize
in setShaderResources() when a referenced QRhiResource has been rebuilt
in the meantime (create() was called i.e. there may be completely
different native objects underneath), QRhiTextureRenderTarget has no
such thing. This leads to an asymmetric API and requires also rebuilding
the rt whenever an attachment is rebuilt:

rt = rhi->newTextureRenderTarget({ { texture } })
rt->create()
cb->beginPass(rt, ...)
texture->setPixelSize(...)
texture->create()
rt->create() // this should not be needed
cb->beginPass(rt, ...)

Avoid having to do that second rt->create().

Change-Id: If14eaa7aac3530950498bbdf834324d0741a7c4d
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Andy Nichols <andy.nichols@qt.io>

1 files changed, 45 insertions, 0 deletions

diff --git a/tests/auto/gui/rhi/qrhi/tst_qrhi.cpp b/tests/auto/gui/rhi/qrhi/tst_qrhi.cpp
index 5142d5566f..89c02322dd 100644
--- a/tests/auto/gui/rhi/qrhi/tst_qrhi.cpp
+++ b/tests/auto/gui/rhi/qrhi/tst_qrhi.cpp
@@ -137,6 +137,8 @@ private slots:
     void finishWithinSwapchainFrame();
     void resourceUpdateBatchBufferTextureWithSwapchainFrames_data();
     void resourceUpdateBatchBufferTextureWithSwapchainFrames();
+    void textureRenderTargetAutoRebuild_data();
+    void textureRenderTargetAutoRebuild();
 
     void pipelineCache_data();
     void pipelineCache();
@@ -3767,6 +3769,49 @@ void tst_QRhi::resourceUpdateBatchBufferTextureWithSwapchainFrames()
     }
 }
 
+void tst_QRhi::textureRenderTargetAutoRebuild_data()
+{
+    rhiTestData();
+}
+
+void tst_QRhi::textureRenderTargetAutoRebuild()
+{
+    QFETCH(QRhi::Implementation, impl);
+    QFETCH(QRhiInitParams *, initParams);
+
+    QScopedPointer<QRhi> rhi(QRhi::create(impl, initParams, QRhi::Flags(), nullptr));
+    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());
+
+    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));
+
+    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();
+}
+
 void tst_QRhi::srbLayoutCompatibility_data()
 {
     rhiTestData();