Basic working compressed texture atlas

This adds experimental automatic atlasing of ETC-compressed textures
(to be expanded to additional formats), similar to existing atlas
support of QImages. It is off by default, and can be enabled with
QSG_ENABLE_COMPRESSED_ATLAS=1.

[ChangeLog] Add experimental automatic atlasing of ETC-compressed
textures (can be enabled with QSG_ENABLE_COMPRESSED_ATLAS=1)

Change-Id: Ia66971f51299d082a569bdfaadb662a3e522bd79
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

4 files changed, 306 insertions, 1 deletions

diff --git a/src/quick/scenegraph/compressedtexture/qsgcompressedatlastexture.cpp b/src/quick/scenegraph/compressedtexture/qsgcompressedatlastexture.cpp
new file mode 100644
index 0000000000..301f2826dc
--- /dev/null
+++ b/src/quick/scenegraph/compressedtexture/qsgcompressedatlastexture.cpp
@@ -0,0 +1,174 @@
+/****************************************************************************
+**
+** Copyright (C) 2018 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtQuick module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "qsgcompressedatlastexture_p.h"
+
+#include <QtCore/QVarLengthArray>
+#include <QtCore/QElapsedTimer>
+#include <QtCore/QtMath>
+
+#include <QtGui/QOpenGLContext>
+#include <QtGui/QGuiApplication>
+#include <QtGui/QScreen>
+#include <QtGui/QSurface>
+#include <QtGui/QWindow>
+#include <QtGui/QOpenGLFunctions>
+#include <QtGui/QOpenGLTexture>
+#include <QDebug>
+
+#include <private/qqmlglobal_p.h>
+#include <private/qquickprofiler_p.h>
+#include <private/qsgtexture_p.h>
+#include <private/qsgcompressedtexture_p.h>
+#include <private/qsgpkmhandler_p.h>
+
+QT_BEGIN_NAMESPACE
+
+static QElapsedTimer qsg_renderer_timer;
+
+namespace QSGCompressedAtlasTexture
+{
+
+Atlas::Atlas(const QSize &size, uint format)
+    : QSGAtlasTexture::AtlasBase(size)
+    , m_format(format)
+{
+}
+
+Atlas::~Atlas()
+{
+}
+
+Texture *Atlas::create(const QByteArray &data, int dataLength, int dataOffset, const QSize &size, const QSize &paddedSize)
+{
+    // No need to lock, as manager already locked it.
+    QRect rect = m_allocator.allocate(paddedSize);
+    if (rect.width() > 0 && rect.height() > 0) {
+        Texture *t = new Texture(this, rect, data, dataLength, dataOffset, size);
+        m_pending_uploads << t;
+        return t;
+    }
+    return 0;
+}
+
+void Atlas::generateTexture()
+{
+    QOpenGLFunctions *funcs = QOpenGLContext::currentContext()->functions();
+    funcs->glCompressedTexImage2D(GL_TEXTURE_2D, 0, m_format,
+                                  m_size.width(), m_size.height(), 0,
+                                  (m_size.width() * m_size.height()) / 2,
+                                  0);
+}
+
+void Atlas::uploadPendingTexture(int i)
+{
+    Texture *texture = static_cast<Texture*>(m_pending_uploads.at(i));
+
+    const QRect &r = texture->atlasSubRect();
+
+    QOpenGLFunctions *funcs = QOpenGLContext::currentContext()->functions();
+    funcs->glCompressedTexSubImage2D(GL_TEXTURE_2D, 0,
+                                     r.x(), r.y(), r.width(), r.height(), m_format,
+                                     texture->sizeInBytes(),
+                                     texture->data().constData() + texture->dataOffset());
+
+    qCDebug(QSG_LOG_TIME_TEXTURE).nospace() << "compressed atlastexture uploaded in: " << qsg_renderer_timer.elapsed()
+                                       << "ms (" << texture->textureSize().width() << "x"
+                                       << texture->textureSize().height() << ")";
+
+    // TODO: consider releasing the data (as is done in the regular atlas)?
+    // The advantage of keeping this data around is that it makes it much easier
+    // to remove the texture from the atlas
+}
+
+Texture::Texture(Atlas *atlas, const QRect &textureRect, const QByteArray &data, int dataLength, int dataOffset, const QSize &size)
+    : QSGAtlasTexture::TextureBase(atlas, textureRect)
+    , m_nonatlas_texture(0)
+    , m_data(data)
+    , m_size(size)
+    , m_dataLength(dataLength)
+    , m_dataOffset(dataOffset)
+{
+    float w = atlas->size().width();
+    float h = atlas->size().height();
+    QRect nopad = atlasSubRect();
+    // offset by half-pixel to prevent bleeding when scaling
+    m_texture_coords_rect = QRectF((nopad.x() + .5) / w,
+                                   (nopad.y() + .5) / h,
+                                   (nopad.width() - 1.) / w,
+                                   (nopad.height() - 1.) / h);
+}
+
+Texture::~Texture()
+{
+    delete m_nonatlas_texture;
+}
+
+bool Texture::hasAlphaChannel() const
+{
+    return QSGCompressedTexture::formatIsOpaque(static_cast<Atlas*>(m_atlas)->format());
+}
+
+QSGTexture *Texture::removedFromAtlas() const
+{
+    if (m_nonatlas_texture) {
+        m_nonatlas_texture->setMipmapFiltering(mipmapFiltering());
+        m_nonatlas_texture->setFiltering(filtering());
+        return m_nonatlas_texture;
+    }
+
+    if (!m_data.isEmpty()) {
+        QSGCompressedTexture::DataPtr texData(QSGCompressedTexture::DataPtr::create());
+        texData->data = m_data;
+        texData->size = m_size;
+        texData->format = static_cast<Atlas*>(m_atlas)->format();
+        texData->hasAlpha = hasAlphaChannel();
+        texData->dataLength = m_dataLength;
+        texData->dataOffset = m_dataOffset;
+        m_nonatlas_texture = new QSGCompressedTexture(texData);
+        m_nonatlas_texture->setMipmapFiltering(mipmapFiltering());
+        m_nonatlas_texture->setFiltering(filtering());
+    }
+
+    return m_nonatlas_texture;
+}
+
+}
+
+QT_END_NAMESPACE
diff --git a/src/quick/scenegraph/compressedtexture/qsgcompressedatlastexture_p.h b/src/quick/scenegraph/compressedtexture/qsgcompressedatlastexture_p.h
new file mode 100644
index 0000000000..59e935b623
--- /dev/null
+++ b/src/quick/scenegraph/compressedtexture/qsgcompressedatlastexture_p.h
@@ -0,0 +1,119 @@
+/****************************************************************************
+**
+** Copyright (C) 2018 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtQuick module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QSGCOMPRESSEDATLASTEXTURE_P_H
+#define QSGCOMPRESSEDATLASTEXTURE_P_H
+
+//
+//  W A R N I N G
+//  -------------
+//
+// This file is not part of the Qt API.  It exists purely as an
+// implementation detail.  This header file may change from version to
+// version without notice, or even be removed.
+//
+// We mean it.
+//
+
+#include <QtCore/QSize>
+
+#include <QtGui/qopengl.h>
+
+#include <QtQuick/QSGTexture>
+#include <QtQuick/private/qsgareaallocator_p.h>
+#include <QtQuick/private/qsgatlastexture_p.h>
+
+QT_BEGIN_NAMESPACE
+
+class QSGCompressedTextureFactory;
+
+namespace QSGCompressedAtlasTexture {
+
+class Texture;
+
+class Atlas : public QSGAtlasTexture::AtlasBase
+{
+public:
+    Atlas(const QSize &size, uint format);
+    ~Atlas();
+
+    void generateTexture() override;
+    void uploadPendingTexture(int i) override;
+
+    Texture *create(const QByteArray &data, int dataLength, int dataOffset, const QSize &size, const QSize &paddedSize);
+
+    uint format() const { return m_format; }
+
+private:
+    uint m_format;
+};
+
+class Texture : public QSGAtlasTexture::TextureBase
+{
+    Q_OBJECT
+public:
+    Texture(Atlas *atlas, const QRect &textureRect, const QByteArray &data, int dataLength, int dataOffset, const QSize &size);
+    ~Texture();
+
+    QSize textureSize() const override { return m_size; }
+    bool hasAlphaChannel() const override;
+    bool hasMipmaps() const override { return false; }
+
+    QRectF normalizedTextureSubRect() const override { return m_texture_coords_rect; }
+
+    QSGTexture *removedFromAtlas() const override;
+
+    const QByteArray &data() const { return m_data; }
+    int sizeInBytes() const { return m_dataLength; }
+    int dataOffset() const { return m_dataOffset; }
+
+private:
+    QRectF m_texture_coords_rect;
+    mutable QSGTexture *m_nonatlas_texture;
+    QByteArray m_data;
+    QSize m_size;
+    int m_dataLength;
+    int m_dataOffset;
+};
+
+}
+
+QT_END_NAMESPACE
+
+#endif
diff --git a/src/quick/scenegraph/compressedtexture/qsgcompressedtexture.cpp b/src/quick/scenegraph/compressedtexture/qsgcompressedtexture.cpp
index 6d51ed9d61..839c562989 100644
--- a/src/quick/scenegraph/compressedtexture/qsgcompressedtexture.cpp
+++ b/src/quick/scenegraph/compressedtexture/qsgcompressedtexture.cpp
@@ -43,6 +43,7 @@
 #include <QOpenGLTexture>
 #include <QOpenGLFunctions>
 #include <QDebug>
+#include <QtQuick/private/qquickwindow_p.h>
 
 QT_BEGIN_NAMESPACE
 
@@ -215,11 +216,17 @@ QSGCompressedTextureFactory::QSGCompressedTextureFactory(const QSGCompressedText
 {
 }
 
-QSGTexture *QSGCompressedTextureFactory::createTexture(QQuickWindow *) const
+QSGTexture *QSGCompressedTextureFactory::createTexture(QQuickWindow *window) const
 {
     if (!m_textureData || !m_textureData->isValid())
         return nullptr;
 
+    // attempt to atlas the texture
+    QSGRenderContext *context = QQuickWindowPrivate::get(window)->context;
+    QSGTexture *t = context->compressedTextureForFactory(this);
+    if (t)
+        return t;
+
     return new QSGCompressedTexture(m_textureData);
 }
 
diff --git a/src/quick/scenegraph/compressedtexture/qsgcompressedtexture_p.h b/src/quick/scenegraph/compressedtexture/qsgcompressedtexture_p.h
index dfedac5558..aa87316809 100644
--- a/src/quick/scenegraph/compressedtexture/qsgcompressedtexture_p.h
+++ b/src/quick/scenegraph/compressedtexture/qsgcompressedtexture_p.h
@@ -103,6 +103,9 @@ protected:
     bool m_uploaded = false;
 };
 
+namespace QSGAtlasTexture {
+    class Manager;
+}
 
 class Q_QUICK_PRIVATE_EXPORT QSGCompressedTextureFactory : public QQuickTextureFactory
 {
@@ -114,6 +117,8 @@ public:
 
 protected:
     QSGCompressedTexture::DataPtr m_textureData;
+private:
+    friend class QSGAtlasTexture::Manager;
 };
 
 QT_END_NAMESPACE