Add the graphics api independent scenegraph port

Opt in via environment variables:
QSG_RHI=1 -> enable using QRhi instead of GL
QSG_RHI_BACKEND -> set to vulkan, metal, d3d11, gl to override the default
(the default is d3d11 on Windows, metal on Mac, gl elsewhere)

Or force a given rhi backend via the existing
QQuickWindow::setSceneGraphBackend().

Otherwise the default behavior is the same as before, the rhi code path
is never active by default.

-no-opengl builds are supported in the sense that they work and default
to the software backend. However, the rhi code path cannot currently be
used in such builds, even though QRhi from qtbase is fully functional
with Vulkan, D3D, or Metal even when qtbase was configured with
-no-opengl. This cannot be utilized by Quick atm due to OpenGL usage
being all over the place in the sources corresponding to the default
backend, and those host the rhi code path as well. This will be cleaned up
hopefully in Qt 6, with the removal all direct OpenGL usage.

Other env.vars.:
QSG_RHI_DEBUG_LAYER=1 -> enable D3D debug or Vulkan validation layer
(assuming the system is set up for this)
QSG_RHI_SHADEREFFECT_DEBUG=1 -> print stuff from ShaderEffect
QSG_SAMPLES=1,2,4,... -> MSAA sample count (but QSurfaceFormat works too)
QT_D3D_ADAPTER_INDEX=0,1,... -> D3D adapter index
QT_VK_PHYSICAL_DEVICE_INDEX=0,1,... -> Vulkan physical device index
QSG_RHI_UINT32_INDEX=1 -> always use uint index data (both
merged/unmerged, convert when needed - with some rhi backends this is
implicit)
QSG_RENDER_LOOP -> to override the render loop as usual. The default
with RHI is threaded for Metal, threaded for Vulkan on Windows, basic
for Vulkan on Linux and Android (to be checked later), while the existing
rules apply for OpenGL.

Not supported when running with QRhi:
  - particles
  - compressed atlases (though this is transparent to the apps)
  - QSGRenderNode
  - QQuickRenderControl
  - QQuickFramebufferObject
  - certain QQuickWindow functionality that depends directly on OpenGL
  - anisotropic filtering for textures
  - native text may lack some gamma correction
  - QSGEngine applicability unclear
  - some QML profiler logs may be incorrect or irrelevant

Change-Id: I7822e99ad79e342e4166275da6e9e66498d76521
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

1 files changed, 809 insertions, 0 deletions

diff --git a/src/quick/scenegraph/qsgopengldistancefieldglyphcache.cpp b/src/quick/scenegraph/qsgopengldistancefieldglyphcache.cpp
new file mode 100644
index 0000000000..0f9ca66ad7
--- /dev/null
+++ b/src/quick/scenegraph/qsgopengldistancefieldglyphcache.cpp
@@ -0,0 +1,809 @@
+/****************************************************************************
+**
+** 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 "qsgopengldistancefieldglyphcache_p.h"
+
+#include <QtCore/qelapsedtimer.h>
+#include <QtCore/qbuffer.h>
+#include <QtCore/qendian.h>
+#include <QtQml/qqmlfile.h>
+
+#include <QtGui/private/qdistancefield_p.h>
+#include <QtGui/private/qopenglcontext_p.h>
+#include <QtQml/private/qqmlglobal_p.h>
+#include <qopenglfunctions.h>
+#include <qopenglframebufferobject.h>
+#include <qmath.h>
+#include "qsgcontext_p.h"
+
+
+#if !defined(QT_OPENGL_ES_2)
+#include <QtGui/qopenglfunctions_3_2_core.h>
+#endif
+
+QT_BEGIN_NAMESPACE
+
+DEFINE_BOOL_CONFIG_OPTION(qmlUseGlyphCacheWorkaround, QML_USE_GLYPHCACHE_WORKAROUND)
+DEFINE_BOOL_CONFIG_OPTION(qsgPreferFullSizeGlyphCacheTextures, QSG_PREFER_FULLSIZE_GLYPHCACHE_TEXTURES)
+
+#if !defined(QSG_OPENGL_DISTANCEFIELD_GLYPH_CACHE_PADDING)
+#  define QSG_OPENGL_DISTANCEFIELD_GLYPH_CACHE_PADDING 2
+#endif
+
+QSGOpenGLDistanceFieldGlyphCache::QSGOpenGLDistanceFieldGlyphCache(QOpenGLContext *c,
+                                                                   const QRawFont &font)
+    : QSGDistanceFieldGlyphCache(font)
+    , m_maxTextureSize(0)
+    , m_maxTextureCount(3)
+    , m_areaAllocator(nullptr)
+    , m_blitProgram(nullptr)
+    , m_blitBuffer(QOpenGLBuffer::VertexBuffer)
+    , m_fboGuard(nullptr)
+    , m_funcs(c->functions())
+#if !defined(QT_OPENGL_ES_2)
+    , m_coreFuncs(nullptr)
+#endif
+{
+    if (Q_LIKELY(m_blitBuffer.create())) {
+        m_blitBuffer.bind();
+        static const GLfloat buffer[16] = {-1.0f, -1.0f, 1.0f, -1.0f, 1.0f, 1.0f, -1.0f, 1.0f,
+                                           0.0f, 0.0f, 1.0f, 0.0f, 1.0f, 1.0f, 0.0f, 1.0f};
+        m_blitBuffer.allocate(buffer, sizeof(buffer));
+        m_blitBuffer.release();
+    } else {
+        qWarning("Buffer creation failed");
+    }
+
+    m_coreProfile = (c->format().profile() == QSurfaceFormat::CoreProfile);
+
+    // Load a pregenerated cache if the font contains one
+    loadPregeneratedCache(font);
+}
+
+QSGOpenGLDistanceFieldGlyphCache::~QSGOpenGLDistanceFieldGlyphCache()
+{
+    for (int i = 0; i < m_textures.count(); ++i)
+        m_funcs->glDeleteTextures(1, &m_textures[i].texture);
+
+    if (m_fboGuard != nullptr)
+        m_fboGuard->free();
+
+    delete m_blitProgram;
+    delete m_areaAllocator;
+}
+
+void QSGOpenGLDistanceFieldGlyphCache::requestGlyphs(const QSet<glyph_t> &glyphs)
+{
+    QList<GlyphPosition> glyphPositions;
+    QVector<glyph_t> glyphsToRender;
+
+    if (m_areaAllocator == nullptr)
+        m_areaAllocator = new QSGAreaAllocator(QSize(maxTextureSize(), m_maxTextureCount * maxTextureSize()));
+
+    for (QSet<glyph_t>::const_iterator it = glyphs.constBegin(); it != glyphs.constEnd() ; ++it) {
+        glyph_t glyphIndex = *it;
+
+        int padding = QSG_OPENGL_DISTANCEFIELD_GLYPH_CACHE_PADDING;
+        QRectF boundingRect = glyphData(glyphIndex).boundingRect;
+        int glyphWidth = qCeil(boundingRect.width()) + distanceFieldRadius() * 2;
+        int glyphHeight = qCeil(boundingRect.height()) + distanceFieldRadius() * 2;
+        QSize glyphSize(glyphWidth + padding * 2, glyphHeight + padding * 2);
+        QRect alloc = m_areaAllocator->allocate(glyphSize);
+
+        if (alloc.isNull()) {
+            // Unallocate unused glyphs until we can allocated the new glyph
+            while (alloc.isNull() && !m_unusedGlyphs.isEmpty()) {
+                glyph_t unusedGlyph = *m_unusedGlyphs.constBegin();
+
+                TexCoord unusedCoord = glyphTexCoord(unusedGlyph);
+                QRectF unusedGlyphBoundingRect = glyphData(unusedGlyph).boundingRect;
+                int unusedGlyphWidth = qCeil(unusedGlyphBoundingRect.width()) + distanceFieldRadius() * 2;
+                int unusedGlyphHeight = qCeil(unusedGlyphBoundingRect.height())  + distanceFieldRadius() * 2;
+                m_areaAllocator->deallocate(QRect(unusedCoord.x - padding,
+                                                  unusedCoord.y - padding,
+                                                  padding * 2 + unusedGlyphWidth,
+                                                  padding * 2 + unusedGlyphHeight));
+
+                m_unusedGlyphs.remove(unusedGlyph);
+                m_glyphsTexture.remove(unusedGlyph);
+                removeGlyph(unusedGlyph);
+
+                alloc = m_areaAllocator->allocate(glyphSize);
+            }
+
+            // Not enough space left for this glyph... skip to the next one
+            if (alloc.isNull())
+                continue;
+        }
+
+        TextureInfo *tex = textureInfo(alloc.y() / maxTextureSize());
+        alloc = QRect(alloc.x(), alloc.y() % maxTextureSize(), alloc.width(), alloc.height());
+
+        tex->allocatedArea |= alloc;
+        Q_ASSERT(tex->padding == padding || tex->padding < 0);
+        tex->padding = padding;
+
+        GlyphPosition p;
+        p.glyph = glyphIndex;
+        p.position = alloc.topLeft() + QPoint(padding, padding);
+
+        glyphPositions.append(p);
+        glyphsToRender.append(glyphIndex);
+        m_glyphsTexture.insert(glyphIndex, tex);
+    }
+
+    setGlyphsPosition(glyphPositions);
+    markGlyphsToRender(glyphsToRender);
+}
+
+void QSGOpenGLDistanceFieldGlyphCache::storeGlyphs(const QList<QDistanceField> &glyphs)
+{
+    typedef QHash<TextureInfo *, QVector<glyph_t> > GlyphTextureHash;
+    typedef GlyphTextureHash::const_iterator GlyphTextureHashConstIt;
+
+    GlyphTextureHash glyphTextures;
+
+    GLint alignment = 4; // default value
+    m_funcs->glGetIntegerv(GL_UNPACK_ALIGNMENT, &alignment);
+
+    // Distance field data is always tightly packed
+    m_funcs->glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
+
+    for (int i = 0; i < glyphs.size(); ++i) {
+        QDistanceField glyph = glyphs.at(i);
+        glyph_t glyphIndex = glyph.glyph();
+        TexCoord c = glyphTexCoord(glyphIndex);
+        TextureInfo *texInfo = m_glyphsTexture.value(glyphIndex);
+
+        resizeTexture(texInfo, texInfo->allocatedArea.width(), texInfo->allocatedArea.height());
+        m_funcs->glBindTexture(GL_TEXTURE_2D, texInfo->texture);
+
+        glyphTextures[texInfo].append(glyphIndex);
+
+        int padding = texInfo->padding;
+        int expectedWidth = qCeil(c.width + c.xMargin * 2);
+        glyph = glyph.copy(-padding, -padding,
+                           expectedWidth + padding  * 2, glyph.height() + padding * 2);
+
+        if (useTextureResizeWorkaround()) {
+            uchar *inBits = glyph.scanLine(0);
+            uchar *outBits = texInfo->image.scanLine(int(c.y) - padding) + int(c.x) - padding;
+            for (int y = 0; y < glyph.height(); ++y) {
+                memcpy(outBits, inBits, glyph.width());
+                inBits += glyph.width();
+                outBits += texInfo->image.width();
+            }
+        }
+
+#if !defined(QT_OPENGL_ES_2)
+        const GLenum format = isCoreProfile() ? GL_RED : GL_ALPHA;
+#else
+        const GLenum format = GL_ALPHA;
+#endif
+        if (useTextureUploadWorkaround()) {
+            for (int i = 0; i < glyph.height(); ++i) {
+                m_funcs->glTexSubImage2D(GL_TEXTURE_2D, 0,
+                                         c.x - padding, c.y + i - padding, glyph.width(),1,
+                                         format, GL_UNSIGNED_BYTE,
+                                         glyph.scanLine(i));
+            }
+        } else {
+            m_funcs->glTexSubImage2D(GL_TEXTURE_2D, 0,
+                                     c.x - padding, c.y - padding, glyph.width(), glyph.height(),
+                                     format, GL_UNSIGNED_BYTE,
+                                     glyph.constBits());
+        }
+    }
+
+    // restore to previous alignment
+    m_funcs->glPixelStorei(GL_UNPACK_ALIGNMENT, alignment);
+
+    for (GlyphTextureHashConstIt i = glyphTextures.constBegin(), cend = glyphTextures.constEnd(); i != cend; ++i) {
+        Texture t;
+        t.textureId = i.key()->texture;
+        t.size = i.key()->size;
+        t.rhiBased = false;
+        setGlyphsTexture(i.value(), t);
+    }
+}
+
+void QSGOpenGLDistanceFieldGlyphCache::referenceGlyphs(const QSet<glyph_t> &glyphs)
+{
+    m_unusedGlyphs -= glyphs;
+}
+
+void QSGOpenGLDistanceFieldGlyphCache::releaseGlyphs(const QSet<glyph_t> &glyphs)
+{
+    m_unusedGlyphs += glyphs;
+}
+
+void QSGOpenGLDistanceFieldGlyphCache::createTexture(TextureInfo *texInfo,
+                                                      int width,
+                                                      int height)
+{
+    QByteArray zeroBuf(width * height, 0);
+    createTexture(texInfo, width, height, zeroBuf.constData());
+}
+
+void QSGOpenGLDistanceFieldGlyphCache::createTexture(TextureInfo *texInfo,
+                                                      int width,
+                                                      int height,
+                                                      const void *pixels)
+{
+    if (useTextureResizeWorkaround() && texInfo->image.isNull()) {
+        texInfo->image = QDistanceField(width, height);
+        memcpy(texInfo->image.bits(), pixels, width * height);
+    }
+
+    while (m_funcs->glGetError() != GL_NO_ERROR) { }
+
+    m_funcs->glGenTextures(1, &texInfo->texture);
+    m_funcs->glBindTexture(GL_TEXTURE_2D, texInfo->texture);
+
+    m_funcs->glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+    m_funcs->glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+    m_funcs->glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+    m_funcs->glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
+#if !defined(QT_OPENGL_ES_2)
+    if (!QOpenGLContext::currentContext()->isOpenGLES())
+        m_funcs->glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAX_LEVEL, 0);
+    const GLint internalFormat = isCoreProfile() ? GL_R8 : GL_ALPHA;
+    const GLenum format = isCoreProfile() ? GL_RED : GL_ALPHA;
+#else
+    const GLint internalFormat = GL_ALPHA;
+    const GLenum format = GL_ALPHA;
+#endif
+
+    m_funcs->glTexImage2D(GL_TEXTURE_2D, 0, internalFormat, width, height, 0, format, GL_UNSIGNED_BYTE, pixels);
+
+    texInfo->size = QSize(width, height);
+
+    GLuint error = m_funcs->glGetError();
+    if (error != GL_NO_ERROR) {
+        m_funcs->glBindTexture(GL_TEXTURE_2D, 0);
+        m_funcs->glDeleteTextures(1, &texInfo->texture);
+        texInfo->texture = 0;
+    }
+
+}
+
+static void freeFramebufferFunc(QOpenGLFunctions *funcs, GLuint id)
+{
+    funcs->glDeleteFramebuffers(1, &id);
+}
+
+void QSGOpenGLDistanceFieldGlyphCache::resizeTexture(TextureInfo *texInfo, int width, int height)
+{
+    QOpenGLContext *ctx = QOpenGLContext::currentContext();
+    Q_ASSERT(ctx);
+
+    int oldWidth = texInfo->size.width();
+    int oldHeight = texInfo->size.height();
+    if (width == oldWidth && height == oldHeight)
+        return;
+
+    GLuint oldTexture = texInfo->texture;
+    createTexture(texInfo, width, height);
+
+    if (!oldTexture)
+        return;
+
+    updateTexture(oldTexture, texInfo->texture, texInfo->size);
+
+#if !defined(QT_OPENGL_ES_2)
+    if (isCoreProfile() && !useTextureResizeWorkaround()) {
+        // For an OpenGL Core Profile we can use http://www.opengl.org/wiki/Framebuffer#Blitting
+        // to efficiently copy the contents of the old texture to the new texture
+        // TODO: Use ARB_copy_image if available of if we have >=4.3 context
+        if (!m_coreFuncs) {
+            m_coreFuncs = ctx->versionFunctions<QOpenGLFunctions_3_2_Core>();
+            Q_ASSERT(m_coreFuncs);
+            m_coreFuncs->initializeOpenGLFunctions();
+        }
+
+        // Create a framebuffer object to which we can attach our old and new textures (to
+        // the first two color buffer attachment points)
+        if (!m_fboGuard) {
+            GLuint fbo;
+            m_coreFuncs->glGenFramebuffers(1, &fbo);
+            m_fboGuard = new QOpenGLSharedResourceGuard(ctx, fbo, freeFramebufferFunc);
+        }
+
+        // Bind the FBO to both the GL_READ_FRAMEBUFFER? and GL_DRAW_FRAMEBUFFER targets
+        m_coreFuncs->glBindFramebuffer(GL_FRAMEBUFFER, m_fboGuard->id());
+
+        // Bind the old texture to GL_COLOR_ATTACHMENT0
+        m_coreFuncs->glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
+                                        GL_TEXTURE_2D, oldTexture, 0);
+
+        // Bind the new texture to GL_COLOR_ATTACHMENT1
+        m_coreFuncs->glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT1,
+                                        GL_TEXTURE_2D, texInfo->texture, 0);
+
+        // Set the source and destination buffers
+        m_coreFuncs->glReadBuffer(GL_COLOR_ATTACHMENT0);
+        m_coreFuncs->glDrawBuffer(GL_COLOR_ATTACHMENT1);
+
+        // Do the blit
+        m_coreFuncs->glBlitFramebuffer(0, 0, oldWidth, oldHeight,
+                                   0, 0, oldWidth, oldHeight,
+                                   GL_COLOR_BUFFER_BIT, GL_NEAREST);
+
+        // Reset the default framebuffer
+        QOpenGLFramebufferObject::bindDefault();
+
+        return;
+    } else if (useTextureResizeWorkaround()) {
+#else
+    if (useTextureResizeWorkaround()) {
+#endif
+        GLint alignment = 4; // default value
+        m_funcs->glGetIntegerv(GL_UNPACK_ALIGNMENT, &alignment);
+        m_funcs->glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
+
+#if !defined(QT_OPENGL_ES_2)
+        const GLenum format = isCoreProfile() ? GL_RED : GL_ALPHA;
+#else
+        const GLenum format = GL_ALPHA;
+#endif
+
+        if (useTextureUploadWorkaround()) {
+            for (int i = 0; i < texInfo->image.height(); ++i) {
+                m_funcs->glTexSubImage2D(GL_TEXTURE_2D, 0,
+                                         0, i, oldWidth, 1,
+                                         format, GL_UNSIGNED_BYTE,
+                                         texInfo->image.scanLine(i));
+            }
+        } else {
+            m_funcs->glTexSubImage2D(GL_TEXTURE_2D, 0,
+                                     0, 0, oldWidth, oldHeight,
+                                     format, GL_UNSIGNED_BYTE,
+                                     texInfo->image.constBits());
+        }
+
+        m_funcs->glPixelStorei(GL_UNPACK_ALIGNMENT, alignment); // restore to previous value
+
+        texInfo->image = texInfo->image.copy(0, 0, width, height);
+        m_funcs->glDeleteTextures(1, &oldTexture);
+        return;
+    }
+
+    if (!m_blitProgram)
+        createBlitProgram();
+
+    Q_ASSERT(m_blitProgram);
+
+    if (!m_fboGuard) {
+        GLuint fbo;
+        m_funcs->glGenFramebuffers(1, &fbo);
+        m_fboGuard = new QOpenGLSharedResourceGuard(ctx, fbo, freeFramebufferFunc);
+    }
+    m_funcs->glBindFramebuffer(GL_FRAMEBUFFER, m_fboGuard->id());
+
+    GLuint tmp_texture;
+    m_funcs->glGenTextures(1, &tmp_texture);
+    m_funcs->glBindTexture(GL_TEXTURE_2D, tmp_texture);
+    m_funcs->glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+    m_funcs->glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+    m_funcs->glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+    m_funcs->glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
+#if !defined(QT_OPENGL_ES_2)
+    if (!ctx->isOpenGLES())
+        m_funcs->glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAX_LEVEL, 0);
+#endif
+    m_funcs->glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, oldWidth, oldHeight, 0,
+                          GL_RGBA, GL_UNSIGNED_BYTE, nullptr);
+    m_funcs->glBindTexture(GL_TEXTURE_2D, 0);
+    m_funcs->glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
+                                    GL_TEXTURE_2D, tmp_texture, 0);
+
+    m_funcs->glActiveTexture(GL_TEXTURE0);
+    m_funcs->glBindTexture(GL_TEXTURE_2D, oldTexture);
+
+    // save current render states
+    GLboolean stencilTestEnabled;
+    GLboolean depthTestEnabled;
+    GLboolean scissorTestEnabled;
+    GLboolean blendEnabled;
+    GLint viewport[4];
+    GLint oldProgram;
+    m_funcs->glGetBooleanv(GL_STENCIL_TEST, &stencilTestEnabled);
+    m_funcs->glGetBooleanv(GL_DEPTH_TEST, &depthTestEnabled);
+    m_funcs->glGetBooleanv(GL_SCISSOR_TEST, &scissorTestEnabled);
+    m_funcs->glGetBooleanv(GL_BLEND, &blendEnabled);
+    m_funcs->glGetIntegerv(GL_VIEWPORT, &viewport[0]);
+    m_funcs->glGetIntegerv(GL_CURRENT_PROGRAM, &oldProgram);
+
+    m_funcs->glDisable(GL_STENCIL_TEST);
+    m_funcs->glDisable(GL_DEPTH_TEST);
+    m_funcs->glDisable(GL_SCISSOR_TEST);
+    m_funcs->glDisable(GL_BLEND);
+
+    m_funcs->glViewport(0, 0, oldWidth, oldHeight);
+
+    const bool vaoInit = m_vao.isCreated();
+    if (isCoreProfile()) {
+        if ( !vaoInit )
+            m_vao.create();
+        m_vao.bind();
+    }
+    m_blitProgram->bind();
+    if (!vaoInit || !isCoreProfile()) {
+        m_blitBuffer.bind();
+
+        m_blitProgram->enableAttributeArray(int(QT_VERTEX_COORDS_ATTR));
+        m_blitProgram->enableAttributeArray(int(QT_TEXTURE_COORDS_ATTR));
+        m_blitProgram->setAttributeBuffer(int(QT_VERTEX_COORDS_ATTR), GL_FLOAT, 0, 2);
+        m_blitProgram->setAttributeBuffer(int(QT_TEXTURE_COORDS_ATTR), GL_FLOAT, 32, 2);
+    }
+    m_blitProgram->disableAttributeArray(int(QT_OPACITY_ATTR));
+    m_blitProgram->setUniformValue("imageTexture", GLuint(0));
+
+    m_funcs->glDrawArrays(GL_TRIANGLE_FAN, 0, 4);
+
+    m_funcs->glBindTexture(GL_TEXTURE_2D, texInfo->texture);
+
+    if (useTextureUploadWorkaround()) {
+        for (int i = 0; i < oldHeight; ++i)
+            m_funcs->glCopyTexSubImage2D(GL_TEXTURE_2D, 0, 0, i, 0, i, oldWidth, 1);
+    } else {
+        m_funcs->glCopyTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, 0, 0, oldWidth, oldHeight);
+    }
+
+    m_funcs->glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
+                                       GL_RENDERBUFFER, 0);
+    m_funcs->glDeleteTextures(1, &tmp_texture);
+    m_funcs->glDeleteTextures(1, &oldTexture);
+
+    QOpenGLFramebufferObject::bindDefault();
+
+    // restore render states
+    if (stencilTestEnabled)
+        m_funcs->glEnable(GL_STENCIL_TEST);
+    if (depthTestEnabled)
+        m_funcs->glEnable(GL_DEPTH_TEST);
+    if (scissorTestEnabled)
+        m_funcs->glEnable(GL_SCISSOR_TEST);
+    if (blendEnabled)
+        m_funcs->glEnable(GL_BLEND);
+    m_funcs->glViewport(viewport[0], viewport[1], viewport[2], viewport[3]);
+    m_funcs->glUseProgram(oldProgram);
+
+    m_blitProgram->disableAttributeArray(int(QT_VERTEX_COORDS_ATTR));
+    m_blitProgram->disableAttributeArray(int(QT_TEXTURE_COORDS_ATTR));
+    if (isCoreProfile())
+        m_vao.release();
+}
+
+bool QSGOpenGLDistanceFieldGlyphCache::useTextureResizeWorkaround() const
+{
+    static bool set = false;
+    static bool useWorkaround = false;
+    if (!set) {
+        QOpenGLContextPrivate *ctx_p = static_cast<QOpenGLContextPrivate *>(QOpenGLContextPrivate::get(QOpenGLContext::currentContext()));
+        useWorkaround = ctx_p->workaround_brokenFBOReadBack
+                || qmlUseGlyphCacheWorkaround(); // on some hardware the workaround is faster (see QTBUG-29264)
+        set = true;
+    }
+    return useWorkaround;
+}
+
+bool QSGOpenGLDistanceFieldGlyphCache::useTextureUploadWorkaround() const
+{
+    static bool set = false;
+    static bool useWorkaround = false;
+    if (!set) {
+        useWorkaround = qstrcmp(reinterpret_cast<const char*>(m_funcs->glGetString(GL_RENDERER)),
+                                "Mali-400 MP") == 0;
+        set = true;
+    }
+    return useWorkaround;
+}
+
+bool QSGOpenGLDistanceFieldGlyphCache::createFullSizeTextures() const
+{
+    return qsgPreferFullSizeGlyphCacheTextures() && glyphCount() > QT_DISTANCEFIELD_HIGHGLYPHCOUNT();
+}
+
+int QSGOpenGLDistanceFieldGlyphCache::maxTextureSize() const
+{
+    if (!m_maxTextureSize)
+        m_funcs->glGetIntegerv(GL_MAX_TEXTURE_SIZE, &m_maxTextureSize);
+    return m_maxTextureSize;
+}
+
+namespace {
+    struct Qtdf {
+        // We need these structs to be tightly packed, but some compilers we use do not
+        // support #pragma pack(1), so we need to hardcode the offsets/sizes in the
+        // file format
+        enum TableSize {
+            HeaderSize = 14,
+            GlyphRecordSize = 46,
+            TextureRecordSize = 17
+        };
+
+        enum Offset {
+            // Header
+            majorVersion        = 0,
+            minorVersion        = 1,
+            pixelSize           = 2,
+            textureSize         = 4,
+            flags               = 8,
+            headerPadding       = 9,
+            numGlyphs           = 10,
+
+            // Glyph record
+            glyphIndex          = 0,
+            textureOffsetX      = 4,
+            textureOffsetY      = 8,
+            textureWidth        = 12,
+            textureHeight       = 16,
+            xMargin             = 20,
+            yMargin             = 24,
+            boundingRectX       = 28,
+            boundingRectY       = 32,
+            boundingRectWidth   = 36,
+            boundingRectHeight  = 40,
+            textureIndex        = 44,
+
+            // Texture record
+            allocatedX          = 0,
+            allocatedY          = 4,
+            allocatedWidth      = 8,
+            allocatedHeight     = 12,
+            texturePadding      = 16
+
+        };
+
+        template <typename T>
+        static inline T fetch(const char *data, Offset offset)
+        {
+            return qFromBigEndian<T>(data + int(offset));
+        }
+    };
+}
+
+bool QSGOpenGLDistanceFieldGlyphCache::loadPregeneratedCache(const QRawFont &font)
+{
+    // The pregenerated data must be loaded first, otherwise the area allocator
+    // will be wrong
+    if (m_areaAllocator != nullptr) {
+        qWarning("Font cache must be loaded before cache is used");
+        return false;
+    }
+
+    static QElapsedTimer timer;
+
+    bool profile = QSG_LOG_TIME_GLYPH().isDebugEnabled();
+    if (profile)
+        timer.start();
+
+    QByteArray qtdfTable = font.fontTable("qtdf");
+    if (qtdfTable.isEmpty())
+        return false;
+
+    typedef QHash<TextureInfo *, QVector<glyph_t> > GlyphTextureHash;
+
+    GlyphTextureHash glyphTextures;
+
+    if (uint(qtdfTable.size()) < Qtdf::HeaderSize) {
+        qWarning("Invalid qtdf table in font '%s'",
+                 qPrintable(font.familyName()));
+        return false;
+    }
+
+    const char *qtdfTableStart = qtdfTable.constData();
+    const char *qtdfTableEnd = qtdfTableStart + qtdfTable.size();
+
+    int padding = 0;
+    int textureCount = 0;
+    {
+        quint8 majorVersion = Qtdf::fetch<quint8>(qtdfTableStart, Qtdf::majorVersion);
+        quint8 minorVersion = Qtdf::fetch<quint8>(qtdfTableStart, Qtdf::minorVersion);
+        if (majorVersion != 5 || minorVersion != 12) {
+            qWarning("Invalid version of qtdf table %d.%d in font '%s'",
+                     majorVersion,
+                     minorVersion,
+                     qPrintable(font.familyName()));
+            return false;
+        }
+
+        qreal pixelSize = qreal(Qtdf::fetch<quint16>(qtdfTableStart, Qtdf::pixelSize));
+        m_maxTextureSize = Qtdf::fetch<quint32>(qtdfTableStart, Qtdf::textureSize);
+        m_doubleGlyphResolution = Qtdf::fetch<quint8>(qtdfTableStart, Qtdf::flags) == 1;
+        padding = Qtdf::fetch<quint8>(qtdfTableStart, Qtdf::headerPadding);
+
+        if (pixelSize <= 0.0) {
+            qWarning("Invalid pixel size in '%s'", qPrintable(font.familyName()));
+            return false;
+        }
+
+        if (m_maxTextureSize <= 0) {
+            qWarning("Invalid texture size in '%s'", qPrintable(font.familyName()));
+            return false;
+        }
+
+        int systemMaxTextureSize;
+        m_funcs->glGetIntegerv(GL_MAX_TEXTURE_SIZE, &systemMaxTextureSize);
+
+        if (m_maxTextureSize > systemMaxTextureSize) {
+            qWarning("System maximum texture size is %d. This is lower than the value in '%s', which is %d",
+                     systemMaxTextureSize,
+                     qPrintable(font.familyName()),
+                     m_maxTextureSize);
+        }
+
+        if (padding != QSG_OPENGL_DISTANCEFIELD_GLYPH_CACHE_PADDING) {
+            qWarning("Padding mismatch in '%s'. Font requires %d, but Qt is compiled with %d.",
+                     qPrintable(font.familyName()),
+                     padding,
+                     QSG_OPENGL_DISTANCEFIELD_GLYPH_CACHE_PADDING);
+        }
+
+        m_referenceFont.setPixelSize(pixelSize);
+
+        quint32 glyphCount = Qtdf::fetch<quint32>(qtdfTableStart, Qtdf::numGlyphs);
+        m_unusedGlyphs.reserve(glyphCount);
+
+        const char *allocatorData = qtdfTableStart + Qtdf::HeaderSize;
+        {
+            m_areaAllocator = new QSGAreaAllocator(QSize(0, 0));
+            allocatorData = m_areaAllocator->deserialize(allocatorData, qtdfTableEnd - allocatorData);
+            if (allocatorData == nullptr)
+                return false;
+        }
+
+        if (m_areaAllocator->size().height() % m_maxTextureSize != 0) {
+            qWarning("Area allocator size mismatch in '%s'", qPrintable(font.familyName()));
+            return false;
+        }
+
+        textureCount = m_areaAllocator->size().height() / m_maxTextureSize;
+        m_maxTextureCount = qMax(m_maxTextureCount, textureCount);
+
+        const char *textureRecord = allocatorData;
+        for (int i = 0; i < textureCount; ++i, textureRecord += Qtdf::TextureRecordSize) {
+            if (textureRecord + Qtdf::TextureRecordSize > qtdfTableEnd) {
+                qWarning("qtdf table too small in font '%s'.",
+                         qPrintable(font.familyName()));
+                return false;
+            }
+
+            TextureInfo *tex = textureInfo(i);
+            tex->allocatedArea.setX(Qtdf::fetch<quint32>(textureRecord, Qtdf::allocatedX));
+            tex->allocatedArea.setY(Qtdf::fetch<quint32>(textureRecord, Qtdf::allocatedY));
+            tex->allocatedArea.setWidth(Qtdf::fetch<quint32>(textureRecord, Qtdf::allocatedWidth));
+            tex->allocatedArea.setHeight(Qtdf::fetch<quint32>(textureRecord, Qtdf::allocatedHeight));
+            tex->padding = Qtdf::fetch<quint8>(textureRecord, Qtdf::texturePadding);
+        }
+
+        const char *glyphRecord = textureRecord;
+        for (quint32 i = 0; i < glyphCount; ++i, glyphRecord += Qtdf::GlyphRecordSize) {
+            if (glyphRecord + Qtdf::GlyphRecordSize > qtdfTableEnd) {
+                qWarning("qtdf table too small in font '%s'.",
+                         qPrintable(font.familyName()));
+                return false;
+            }
+
+            glyph_t glyph = Qtdf::fetch<quint32>(glyphRecord, Qtdf::glyphIndex);
+            m_unusedGlyphs.insert(glyph);
+
+            GlyphData &glyphData = emptyData(glyph);
+
+#define FROM_FIXED_POINT(value) \
+(((qreal)value)/(qreal)65536)
+
+            glyphData.texCoord.x = FROM_FIXED_POINT(Qtdf::fetch<quint32>(glyphRecord, Qtdf::textureOffsetX));
+            glyphData.texCoord.y = FROM_FIXED_POINT(Qtdf::fetch<quint32>(glyphRecord, Qtdf::textureOffsetY));
+            glyphData.texCoord.width = FROM_FIXED_POINT(Qtdf::fetch<quint32>(glyphRecord, Qtdf::textureWidth));
+            glyphData.texCoord.height = FROM_FIXED_POINT(Qtdf::fetch<quint32>(glyphRecord, Qtdf::textureHeight));
+            glyphData.texCoord.xMargin = FROM_FIXED_POINT(Qtdf::fetch<quint32>(glyphRecord, Qtdf::xMargin));
+            glyphData.texCoord.yMargin = FROM_FIXED_POINT(Qtdf::fetch<quint32>(glyphRecord, Qtdf::yMargin));
+            glyphData.boundingRect.setX(FROM_FIXED_POINT(Qtdf::fetch<qint32>(glyphRecord, Qtdf::boundingRectX)));
+            glyphData.boundingRect.setY(FROM_FIXED_POINT(Qtdf::fetch<qint32>(glyphRecord, Qtdf::boundingRectY)));
+            glyphData.boundingRect.setWidth(FROM_FIXED_POINT(Qtdf::fetch<quint32>(glyphRecord, Qtdf::boundingRectWidth)));
+            glyphData.boundingRect.setHeight(FROM_FIXED_POINT(Qtdf::fetch<quint32>(glyphRecord, Qtdf::boundingRectHeight)));
+
+#undef FROM_FIXED_POINT
+
+            int textureIndex = Qtdf::fetch<quint16>(glyphRecord, Qtdf::textureIndex);
+            if (textureIndex < 0 || textureIndex >= textureCount) {
+                qWarning("Invalid texture index %d (texture count == %d) in '%s'",
+                         textureIndex,
+                         textureCount,
+                         qPrintable(font.familyName()));
+                return false;
+            }
+
+
+            TextureInfo *texInfo = textureInfo(textureIndex);
+            m_glyphsTexture.insert(glyph, texInfo);
+
+            glyphTextures[texInfo].append(glyph);
+        }
+
+        GLint alignment = 4; // default value
+        m_funcs->glGetIntegerv(GL_UNPACK_ALIGNMENT, &alignment);
+
+        m_funcs->glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
+
+        const uchar *textureData = reinterpret_cast<const uchar *>(glyphRecord);
+        for (int i = 0; i < textureCount; ++i) {
+
+            TextureInfo *texInfo = textureInfo(i);
+
+            int width = texInfo->allocatedArea.width();
+            int height = texInfo->allocatedArea.height();
+            qint64 size = width * height;
+            if (reinterpret_cast<const char *>(textureData + size) > qtdfTableEnd) {
+                qWarning("qtdf table too small in font '%s'.",
+                         qPrintable(font.familyName()));
+                return false;
+            }
+
+            createTexture(texInfo, width, height, textureData);
+
+            QVector<glyph_t> glyphs = glyphTextures.value(texInfo);
+
+            Texture t;
+            t.textureId = texInfo->texture;
+            t.size = texInfo->size;
+            t.rhiBased = false;
+
+            setGlyphsTexture(glyphs, t);
+
+            textureData += size;
+        }
+
+        m_funcs->glPixelStorei(GL_UNPACK_ALIGNMENT, alignment);
+    }
+
+    if (profile) {
+        quint64 now = timer.elapsed();
+        qCDebug(QSG_LOG_TIME_GLYPH,
+                "distancefield: %d pre-generated glyphs loaded in %dms",
+                m_unusedGlyphs.size(),
+                (int) now);
+    }
+
+    return true;
+}
+
+QT_END_NAMESPACE