rhi: Autotest basic texture operations

...and make the Null backend able to deal with these, for RGBA8 textures
at least. Naturally it is all QImage and QPainter under the hood.

Also fix a bug in the OpenGL backend, as discovered by the autotest:
the size from the readback did not reflect the mip level.

Task-number: QTBUG-78971
Change-Id: Ie424b268bf5feb09021099b67068f4418a9b583e
Reviewed-by: Paul Olav Tvete <paul.tvete@qt.io>

3 files changed, 114 insertions, 12 deletions

diff --git a/src/gui/rhi/qrhigles2.cpp b/src/gui/rhi/qrhigles2.cpp
index 13dc016fd6..a6094183fb 100644
--- a/src/gui/rhi/qrhigles2.cpp
+++ b/src/gui/rhi/qrhigles2.cpp
@@ -1532,8 +1532,9 @@ void QRhiGles2::enqueueResourceUpdates(QRhiCommandBuffer *cb, QRhiResourceUpdate
                 trackedImageBarrier(cbD, texD, QGles2Texture::AccessRead);
             cmd.args.readPixels.texture = texD ? texD->texture : 0;
             if (texD) {
-                cmd.args.readPixels.w = texD->m_pixelSize.width();
-                cmd.args.readPixels.h = texD->m_pixelSize.height();
+                const QSize readImageSize = q->sizeForMipLevel(u.rb.level(), texD->m_pixelSize);
+                cmd.args.readPixels.w = readImageSize.width();
+                cmd.args.readPixels.h = readImageSize.height();
                 cmd.args.readPixels.format = texD->m_format;
                 const GLenum faceTargetBase = texD->m_flags.testFlag(QRhiTexture::CubeMap)
                         ? GL_TEXTURE_CUBE_MAP_POSITIVE_X : texD->target;
diff --git a/src/gui/rhi/qrhinull.cpp b/src/gui/rhi/qrhinull.cpp
index de6616b677..d78b5e20c5 100644
--- a/src/gui/rhi/qrhinull.cpp
+++ b/src/gui/rhi/qrhinull.cpp
@@ -36,6 +36,7 @@
 
 #include "qrhinull_p_p.h"
 #include <qmath.h>
+#include <QPainter>
 
 QT_BEGIN_NAMESPACE
 
@@ -385,6 +386,67 @@ QRhi::FrameOpResult QRhiNull::finish()
     return QRhi::FrameOpSuccess;
 }
 
+void QRhiNull::simulateTextureUpload(const QRhiResourceUpdateBatchPrivate::TextureOp &u)
+{
+    QNullTexture *texD = QRHI_RES(QNullTexture, u.dst);
+    for (int layer = 0; layer < QRhi::MAX_LAYERS; ++layer) {
+        for (int level = 0; level < QRhi::MAX_LEVELS; ++level) {
+            for (const QRhiTextureSubresourceUploadDescription &subresDesc : qAsConst(u.subresDesc[layer][level])) {
+                if (!subresDesc.image().isNull()) {
+                    const QImage src = subresDesc.image();
+                    QPainter painter(&texD->image[layer][level]);
+                    const QSize srcSize = subresDesc.sourceSize().isEmpty()
+                            ? src.size() : subresDesc.sourceSize();
+                    painter.drawImage(subresDesc.destinationTopLeft(), src,
+                                      QRect(subresDesc.sourceTopLeft(), srcSize));
+                } else if (!subresDesc.data().isEmpty()) {
+                    const QSize subresSize = q->sizeForMipLevel(level, texD->pixelSize());
+                    int w = subresSize.width();
+                    int h = subresSize.height();
+                    if (!subresDesc.sourceSize().isEmpty()) {
+                        w = subresDesc.sourceSize().width();
+                        h = subresDesc.sourceSize().height();
+                    }
+                    // sourceTopLeft is not supported on this path as per QRhi docs
+                    const char *src = subresDesc.data().constData();
+                    const int srcBpl = w * 4;
+                    const QPoint dstOffset = subresDesc.destinationTopLeft();
+                    uchar *dst = texD->image[layer][level].bits();
+                    const int dstBpl = texD->image[layer][level].bytesPerLine();
+                    for (int y = 0; y < h; ++y) {
+                        memcpy(dst + dstOffset.x() * 4 + (y + dstOffset.y()) * dstBpl,
+                               src + y * srcBpl,
+                               size_t(srcBpl));
+                    }
+                }
+            }
+        }
+    }
+}
+
+void QRhiNull::simulateTextureCopy(const QRhiResourceUpdateBatchPrivate::TextureOp &u)
+{
+    QNullTexture *srcD = QRHI_RES(QNullTexture, u.src);
+    QNullTexture *dstD = QRHI_RES(QNullTexture, u.dst);
+    const QImage &srcImage(srcD->image[u.desc.sourceLayer()][u.desc.sourceLevel()]);
+    QImage &dstImage(dstD->image[u.desc.destinationLayer()][u.desc.destinationLevel()]);
+    const QPoint dstPos = u.desc.destinationTopLeft();
+    const QSize size = u.desc.pixelSize().isEmpty() ? srcD->pixelSize() : u.desc.pixelSize();
+    const QPoint srcPos = u.desc.sourceTopLeft();
+
+    QPainter painter(&dstImage);
+    painter.drawImage(QRect(dstPos, size), srcImage, QRect(srcPos, size));
+}
+
+void QRhiNull::simulateTextureGenMips(const QRhiResourceUpdateBatchPrivate::TextureOp &u)
+{
+    QNullTexture *texD = QRHI_RES(QNullTexture, u.dst);
+    const QSize baseSize = texD->pixelSize();
+    const int levelCount = q->mipLevelsForSize(baseSize);
+    for (int level = 1; level < levelCount; ++level)
+        texD->image[0][level] = texD->image[0][0].scaled(q->sizeForMipLevel(level, baseSize));
+}
+
 void QRhiNull::resourceUpdate(QRhiCommandBuffer *cb, QRhiResourceUpdateBatch *resourceUpdates)
 {
     Q_UNUSED(cb);
@@ -405,22 +467,42 @@ void QRhiNull::resourceUpdate(QRhiCommandBuffer *cb, QRhiResourceUpdateBatch *re
         }
     }
     for (const QRhiResourceUpdateBatchPrivate::TextureOp &u : ud->textureOps) {
-        if (u.type == QRhiResourceUpdateBatchPrivate::TextureOp::Read) {
+        if (u.type == QRhiResourceUpdateBatchPrivate::TextureOp::Upload) {
+            if (u.dst->format() == QRhiTexture::RGBA8)
+                simulateTextureUpload(u);
+        } else if (u.type == QRhiResourceUpdateBatchPrivate::TextureOp::Copy) {
+            if (u.src->format() == QRhiTexture::RGBA8 && u.dst->format() == QRhiTexture::RGBA8)
+                simulateTextureCopy(u);
+        } else if (u.type == QRhiResourceUpdateBatchPrivate::TextureOp::Read) {
             QRhiReadbackResult *result = u.result;
-            QRhiTexture *tex = u.rb.texture();
-            if (tex) {
-                result->format = tex->format();
-                result->pixelSize = q->sizeForMipLevel(u.rb.level(), tex->pixelSize());
+            QNullTexture *texD = QRHI_RES(QNullTexture, u.rb.texture());
+            if (texD) {
+                result->format = texD->format();
+                result->pixelSize = q->sizeForMipLevel(u.rb.level(), texD->pixelSize());
             } else {
                 Q_ASSERT(currentSwapChain);
                 result->format = QRhiTexture::RGBA8;
                 result->pixelSize = currentSwapChain->currentPixelSize();
             }
+            quint32 bytesPerLine = 0;
             quint32 byteSize = 0;
-            textureFormatInfo(result->format, result->pixelSize, nullptr, &byteSize);
-            result->data.fill(0, int(byteSize));
+            textureFormatInfo(result->format, result->pixelSize, &bytesPerLine, &byteSize);
+            if (result->format == QRhiTexture::RGBA8) {
+                result->data.resize(int(byteSize));
+                const QImage &src(texD->image[u.rb.layer()][u.rb.level()]);
+                char *dst = result->data.data();
+                for (int y = 0, h = src.height(); y < h; ++y) {
+                    memcpy(dst, src.constScanLine(y), bytesPerLine);
+                    dst += bytesPerLine;
+                }
+            } else {
+                result->data.fill(0, int(byteSize));
+            }
             if (result->completed)
                 result->completed();
+        } else if (u.type == QRhiResourceUpdateBatchPrivate::TextureOp::GenMips) {
+            if (u.dst->format() == QRhiTexture::RGBA8)
+                simulateTextureGenMips(u);
         }
     }
     ud->free();
@@ -532,22 +614,36 @@ void QNullTexture::release()
 
 bool QNullTexture::build()
 {
+    QRHI_RES_RHI(QRhiNull);
     const bool isCube = m_flags.testFlag(CubeMap);
     const bool hasMipMaps = m_flags.testFlag(MipMapped);
     QSize size = m_pixelSize.isEmpty() ? QSize(1, 1) : m_pixelSize;
-    const int mipLevelCount = hasMipMaps ? qCeil(log2(qMax(size.width(), size.height()))) + 1 : 1;
+    const int mipLevelCount = hasMipMaps ? rhiD->q->mipLevelsForSize(size) : 1;
+    const int layerCount = isCube ? 6 : 1;
+
+    if (m_format == RGBA8) {
+        for (int layer = 0; layer < layerCount; ++layer) {
+            for (int level = 0; level < mipLevelCount; ++level) {
+                image[layer][level] = QImage(rhiD->q->sizeForMipLevel(level, size),
+                                             QImage::Format_RGBA8888_Premultiplied);
+                image[layer][level].fill(Qt::yellow);
+            }
+        }
+    }
+
     QRHI_PROF;
-    QRHI_PROF_F(newTexture(this, true, mipLevelCount, isCube ? 6 : 1, 1));
+    QRHI_PROF_F(newTexture(this, true, mipLevelCount, layerCount, 1));
     return true;
 }
 
 bool QNullTexture::buildFrom(const QRhiNativeHandles *src)
 {
     Q_UNUSED(src);
+    QRHI_RES_RHI(QRhiNull);
     const bool isCube = m_flags.testFlag(CubeMap);
     const bool hasMipMaps = m_flags.testFlag(MipMapped);
     QSize size = m_pixelSize.isEmpty() ? QSize(1, 1) : m_pixelSize;
-    const int mipLevelCount = hasMipMaps ? qCeil(log2(qMax(size.width(), size.height()))) + 1 : 1;
+    const int mipLevelCount = hasMipMaps ? rhiD->q->mipLevelsForSize(size) : 1;
     QRHI_PROF;
     QRHI_PROF_F(newTexture(this, false, mipLevelCount, isCube ? 6 : 1, 1));
     return true;
diff --git a/src/gui/rhi/qrhinull_p_p.h b/src/gui/rhi/qrhinull_p_p.h
index 93e298481c..ce517bfa63 100644
--- a/src/gui/rhi/qrhinull_p_p.h
+++ b/src/gui/rhi/qrhinull_p_p.h
@@ -84,6 +84,7 @@ struct QNullTexture : public QRhiTexture
     const QRhiNativeHandles *nativeHandles() override;
 
     QRhiNullTextureNativeHandles nativeHandlesStruct;
+    QImage image[QRhi::MAX_LAYERS][QRhi::MAX_LEVELS];
 };
 
 struct QNullSampler : public QRhiSampler
@@ -288,6 +289,10 @@ public:
     void releaseCachedResources() override;
     bool isDeviceLost() const override;
 
+    void simulateTextureUpload(const QRhiResourceUpdateBatchPrivate::TextureOp &u);
+    void simulateTextureCopy(const QRhiResourceUpdateBatchPrivate::TextureOp &u);
+    void simulateTextureGenMips(const QRhiResourceUpdateBatchPrivate::TextureOp &u);
+
     QRhiNullNativeHandles nativeHandlesStruct;
     QRhiSwapChain *currentSwapChain = nullptr;
     QNullCommandBuffer offscreenCommandBuffer;