Move backing store OpenGL support to the platformcompositor module

QPlatformBackingStore had a dependency on the QOpenGLTextureBlitter, which is a
problem because we want to get rid of all the public QOpenGL* classes in the
gui module.

This splits the heavily QOpenGL dependent parts of the backing store
implementation into a separate class and moves it to the platformcompositor
module.

qplatformbackingstore.cpp is now mostly free from OpenGL implementation
details.

Platform integrations now have to explicitly request backing store OpenGL
support. This has been done for:

- xcb
- windows
- cocoa
- winrt
- android
- wasm
- ios

QPlatformGraphicsBufferHelper::lockAndBindToTexture is now exported so it can
be used from other modules.

Task-number: QTBUG-74409
Change-Id: I42ad9250e5a424939cf751a8ad880c7381ede2ae
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

1 files changed, 456 insertions, 0 deletions

diff --git a/src/platformsupport/platformcompositor/qplatformbackingstoreopenglsupport.cpp b/src/platformsupport/platformcompositor/qplatformbackingstoreopenglsupport.cpp
new file mode 100644
index 0000000000..bcd2b90a87
--- /dev/null
+++ b/src/platformsupport/platformcompositor/qplatformbackingstoreopenglsupport.cpp
@@ -0,0 +1,456 @@
+/****************************************************************************
+**
+** Copyright (C) 2020 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtGui 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 QT_NO_OPENGL
+
+#include "qplatformbackingstoreopenglsupport.h"
+
+#include <QtGui/private/qwindow_p.h>
+
+#include <qpa/qplatformgraphicsbuffer.h>
+#include <qpa/qplatformgraphicsbufferhelper.h>
+
+#include <QtGui/qopengl.h>
+#include <QtGui/QOpenGLFunctions>
+#include <QtGui/QOpenGLContext>
+#include <QtGui/QOpenGLTextureBlitter>
+
+#include <QtGui/QOffscreenSurface>
+
+#ifndef GL_TEXTURE_BASE_LEVEL
+#define GL_TEXTURE_BASE_LEVEL             0x813C
+#endif
+#ifndef GL_TEXTURE_MAX_LEVEL
+#define GL_TEXTURE_MAX_LEVEL              0x813D
+#endif
+#ifndef GL_UNPACK_ROW_LENGTH
+#define GL_UNPACK_ROW_LENGTH              0x0CF2
+#endif
+#ifndef GL_RGB10_A2
+#define GL_RGB10_A2                       0x8059
+#endif
+#ifndef GL_UNSIGNED_INT_2_10_10_10_REV
+#define GL_UNSIGNED_INT_2_10_10_10_REV    0x8368
+#endif
+
+#ifndef GL_FRAMEBUFFER_SRGB
+#define GL_FRAMEBUFFER_SRGB 0x8DB9
+#endif
+#ifndef GL_FRAMEBUFFER_SRGB_CAPABLE
+#define GL_FRAMEBUFFER_SRGB_CAPABLE 0x8DBA
+#endif
+
+QT_BEGIN_NAMESPACE
+
+static inline QRect deviceRect(const QRect &rect, QWindow *window)
+{
+    QRect deviceRect(rect.topLeft() * window->devicePixelRatio(),
+                     rect.size() * window->devicePixelRatio());
+    return deviceRect;
+}
+
+static inline QPoint deviceOffset(const QPoint &pt, QWindow *window)
+{
+    return pt * window->devicePixelRatio();
+}
+
+static QRegion deviceRegion(const QRegion &region, QWindow *window, const QPoint &offset)
+{
+    if (offset.isNull() && window->devicePixelRatio() <= 1)
+        return region;
+
+    QVector<QRect> rects;
+    rects.reserve(region.rectCount());
+    for (const QRect &rect : region)
+        rects.append(deviceRect(rect.translated(offset), window));
+
+    QRegion deviceRegion;
+    deviceRegion.setRects(rects.constData(), rects.count());
+    return deviceRegion;
+}
+
+static inline QRect toBottomLeftRect(const QRect &topLeftRect, int windowHeight)
+{
+    return QRect(topLeftRect.x(), windowHeight - topLeftRect.bottomRight().y() - 1,
+                 topLeftRect.width(), topLeftRect.height());
+}
+
+static void blitTextureForWidget(const QPlatformTextureList *textures, int idx, QWindow *window, const QRect &deviceWindowRect,
+                                 QOpenGLTextureBlitter *blitter, const QPoint &offset, bool canUseSrgb)
+{
+    const QRect clipRect = textures->clipRect(idx);
+    if (clipRect.isEmpty())
+        return;
+
+    QRect rectInWindow = textures->geometry(idx);
+    // relative to the TLW, not necessarily our window (if the flush is for a native child widget), have to adjust
+    rectInWindow.translate(-offset);
+
+    const QRect clippedRectInWindow = rectInWindow & clipRect.translated(rectInWindow.topLeft());
+    const QRect srcRect = toBottomLeftRect(clipRect, rectInWindow.height());
+
+    const QMatrix4x4 target = QOpenGLTextureBlitter::targetTransform(deviceRect(clippedRectInWindow, window),
+                                                                     deviceWindowRect);
+
+    const QMatrix3x3 source = QOpenGLTextureBlitter::sourceTransform(deviceRect(srcRect, window),
+                                                                     deviceRect(rectInWindow, window).size(),
+                                                                     QOpenGLTextureBlitter::OriginBottomLeft);
+
+    QOpenGLFunctions *funcs = QOpenGLContext::currentContext()->functions();
+    const bool srgb = textures->flags(idx).testFlag(QPlatformTextureList::TextureIsSrgb);
+    if (srgb && canUseSrgb)
+        funcs->glEnable(GL_FRAMEBUFFER_SRGB);
+
+    blitter->blit(textures->textureId(idx), target, source);
+
+    if (srgb && canUseSrgb)
+        funcs->glDisable(GL_FRAMEBUFFER_SRGB);
+}
+
+QPlatformBackingStoreOpenGLSupport::~QPlatformBackingStoreOpenGLSupport() {
+    if (context) {
+        QOffscreenSurface offscreenSurface;
+        offscreenSurface.setFormat(context->format());
+        offscreenSurface.create();
+        context->makeCurrent(&offscreenSurface);
+        if (textureId)
+            context->functions()->glDeleteTextures(1, &textureId);
+        if (blitter)
+            blitter->destroy();
+    }
+    delete blitter;
+}
+
+void QPlatformBackingStoreOpenGLSupport::composeAndFlush(QWindow *window, const QRegion &region, const QPoint &offset, QPlatformTextureList *textures, bool translucentBackground)
+{
+    if (!qt_window_private(window)->receivedExpose)
+        return;
+
+    if (!context) {
+        context.reset(new QOpenGLContext);
+        context->setFormat(window->requestedFormat());
+        context->setScreen(window->screen());
+        context->setShareContext(qt_window_private(window)->shareContext());
+        if (!context->create()) {
+            qCWarning(lcQpaBackingStore, "composeAndFlush: QOpenGLContext creation failed");
+            return;
+        }
+    }
+
+    bool current = context->makeCurrent(window);
+
+    if (!current && context->isValid()) {
+        delete blitter;
+        blitter = nullptr;
+        textureId = 0;
+        current = context->create() && context->makeCurrent(window);
+    }
+
+    if (!current) {
+        qCWarning(lcQpaBackingStore, "composeAndFlush: makeCurrent() failed");
+        return;
+    }
+
+    qCDebug(lcQpaBackingStore) << "Composing and flushing" << region << "of" << window
+        << "at offset" << offset << "with" << textures->count() << "texture(s) in" << textures;
+
+    QWindowPrivate::get(window)->lastComposeTime.start();
+
+    QOpenGLFunctions *funcs = context->functions();
+    funcs->glViewport(0, 0, qRound(window->width() * window->devicePixelRatio()), qRound(window->height() * window->devicePixelRatio()));
+    funcs->glClearColor(0, 0, 0, translucentBackground ? 0 : 1);
+    funcs->glClear(GL_COLOR_BUFFER_BIT);
+
+    if (!blitter) {
+        blitter = new QOpenGLTextureBlitter;
+        blitter->create();
+    }
+
+    blitter->bind();
+
+    const QRect deviceWindowRect = deviceRect(QRect(QPoint(), window->size()), window);
+    const QPoint deviceWindowOffset = deviceOffset(offset, window);
+
+    bool canUseSrgb = false;
+    // If there are any sRGB textures in the list, check if the destination
+    // framebuffer is sRGB capable.
+    for (int i = 0; i < textures->count(); ++i) {
+        if (textures->flags(i).testFlag(QPlatformTextureList::TextureIsSrgb)) {
+            GLint cap = 0;
+            funcs->glGetIntegerv(GL_FRAMEBUFFER_SRGB_CAPABLE, &cap);
+            if (cap)
+                canUseSrgb = true;
+            break;
+        }
+    }
+
+    // Textures for renderToTexture widgets.
+    for (int i = 0; i < textures->count(); ++i) {
+        if (!textures->flags(i).testFlag(QPlatformTextureList::StacksOnTop))
+            blitTextureForWidget(textures, i, window, deviceWindowRect, blitter, offset, canUseSrgb);
+    }
+
+    // Backingstore texture with the normal widgets.
+    GLuint textureId = 0;
+    QOpenGLTextureBlitter::Origin origin = QOpenGLTextureBlitter::OriginTopLeft;
+    if (QPlatformGraphicsBuffer *graphicsBuffer = backingStore->graphicsBuffer()) {
+        if (graphicsBuffer->size() != textureSize) {
+            if (this->textureId)
+                funcs->glDeleteTextures(1, &this->textureId);
+            funcs->glGenTextures(1, &this->textureId);
+            funcs->glBindTexture(GL_TEXTURE_2D, this->textureId);
+            QOpenGLContext *ctx = QOpenGLContext::currentContext();
+            if (!ctx->isOpenGLES() || ctx->format().majorVersion() >= 3) {
+                funcs->glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_BASE_LEVEL, 0);
+                funcs->glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAX_LEVEL, 0);
+            }
+            funcs->glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+            funcs->glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+            funcs->glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+            funcs->glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
+
+            if (QPlatformGraphicsBufferHelper::lockAndBindToTexture(graphicsBuffer, &needsSwizzle, &premultiplied)) {
+                textureSize = graphicsBuffer->size();
+            } else {
+                textureSize = QSize(0,0);
+            }
+
+            graphicsBuffer->unlock();
+        } else if (!region.isEmpty()){
+            funcs->glBindTexture(GL_TEXTURE_2D, this->textureId);
+            QPlatformGraphicsBufferHelper::lockAndBindToTexture(graphicsBuffer, &needsSwizzle, &premultiplied);
+            graphicsBuffer->unlock();
+        }
+
+        if (graphicsBuffer->origin() == QPlatformGraphicsBuffer::OriginBottomLeft)
+            origin = QOpenGLTextureBlitter::OriginBottomLeft;
+        textureId = this->textureId;
+    } else {
+        QPlatformBackingStore::TextureFlags flags;
+        textureId = backingStore->toTexture(deviceRegion(region, window, offset), &textureSize, &flags);
+        needsSwizzle = (flags & QPlatformBackingStore::TextureSwizzle) != 0;
+        premultiplied = (flags & QPlatformBackingStore::TexturePremultiplied) != 0;
+        if (flags & QPlatformBackingStore::TextureFlip)
+            origin = QOpenGLTextureBlitter::OriginBottomLeft;
+    }
+
+    funcs->glEnable(GL_BLEND);
+    if (premultiplied)
+        funcs->glBlendFuncSeparate(GL_ONE, GL_ONE_MINUS_SRC_ALPHA, GL_ONE, GL_ONE);
+    else
+        funcs->glBlendFuncSeparate(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA, GL_ONE, GL_ONE);
+
+    if (textureId) {
+        if (needsSwizzle)
+            blitter->setRedBlueSwizzle(true);
+        // The backingstore is for the entire tlw.
+        // In case of native children offset tells the position relative to the tlw.
+        const QRect srcRect = toBottomLeftRect(deviceWindowRect.translated(deviceWindowOffset), textureSize.height());
+        const QMatrix3x3 source = QOpenGLTextureBlitter::sourceTransform(srcRect,
+                                                                         textureSize,
+                                                                         origin);
+        blitter->blit(textureId, QMatrix4x4(), source);
+        if (needsSwizzle)
+            blitter->setRedBlueSwizzle(false);
+    }
+
+    // Textures for renderToTexture widgets that have WA_AlwaysStackOnTop set.
+    bool blendIsPremultiplied = premultiplied;
+    for (int i = 0; i < textures->count(); ++i) {
+        const QPlatformTextureList::Flags flags = textures->flags(i);
+        if (flags.testFlag(QPlatformTextureList::NeedsPremultipliedAlphaBlending)) {
+            if (!blendIsPremultiplied) {
+                funcs->glBlendFuncSeparate(GL_ONE, GL_ONE_MINUS_SRC_ALPHA, GL_ONE, GL_ONE);
+                blendIsPremultiplied = true;
+            }
+        } else {
+            if (blendIsPremultiplied) {
+                funcs->glBlendFuncSeparate(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA, GL_ONE, GL_ONE);
+                blendIsPremultiplied = false;
+            }
+        }
+        if (flags.testFlag(QPlatformTextureList::StacksOnTop))
+            blitTextureForWidget(textures, i, window, deviceWindowRect, blitter, offset, canUseSrgb);
+    }
+
+    funcs->glDisable(GL_BLEND);
+    blitter->release();
+
+    context->swapBuffers(window);
+}
+
+GLuint QPlatformBackingStoreOpenGLSupport::toTexture(const QRegion &dirtyRegion, QSize *textureSize, QPlatformBackingStore::TextureFlags *flags) const
+{
+    Q_ASSERT(textureSize);
+    Q_ASSERT(flags);
+
+    QImage image = backingStore->toImage();
+    QSize imageSize = image.size();
+
+    QOpenGLContext *ctx = QOpenGLContext::currentContext();
+    GLenum internalFormat = GL_RGBA;
+    GLuint pixelType = GL_UNSIGNED_BYTE;
+
+    bool needsConversion = false;
+    *flags = { };
+    switch (image.format()) {
+    case QImage::Format_ARGB32_Premultiplied:
+        *flags |= QPlatformBackingStore::TexturePremultiplied;
+        Q_FALLTHROUGH();
+    case QImage::Format_RGB32:
+    case QImage::Format_ARGB32:
+        *flags |= QPlatformBackingStore::TextureSwizzle;
+        break;
+    case QImage::Format_RGBA8888_Premultiplied:
+        *flags |= QPlatformBackingStore::TexturePremultiplied;
+        Q_FALLTHROUGH();
+    case QImage::Format_RGBX8888:
+    case QImage::Format_RGBA8888:
+        break;
+    case QImage::Format_BGR30:
+    case QImage::Format_A2BGR30_Premultiplied:
+        if (!ctx->isOpenGLES() || ctx->format().majorVersion() >= 3) {
+            pixelType = GL_UNSIGNED_INT_2_10_10_10_REV;
+            internalFormat = GL_RGB10_A2;
+            *flags |= QPlatformBackingStore::TexturePremultiplied;
+        } else {
+            needsConversion = true;
+        }
+        break;
+    case QImage::Format_RGB30:
+    case QImage::Format_A2RGB30_Premultiplied:
+        if (!ctx->isOpenGLES() || ctx->format().majorVersion() >= 3) {
+            pixelType = GL_UNSIGNED_INT_2_10_10_10_REV;
+            internalFormat = GL_RGB10_A2;
+            *flags |= QPlatformBackingStore::TextureSwizzle | QPlatformBackingStore::TexturePremultiplied;
+        } else {
+            needsConversion = true;
+        }
+        break;
+    default:
+        needsConversion = true;
+        break;
+    }
+    if (imageSize.isEmpty()) {
+        *textureSize = imageSize;
+        return 0;
+    }
+
+    // Must rely on the input only, not d_ptr.
+    // With the default composeAndFlush() textureSize is &d_ptr->textureSize.
+    bool resized = *textureSize != imageSize;
+    if (dirtyRegion.isEmpty() && !resized)
+        return textureId;
+
+    *textureSize = imageSize;
+
+    if (needsConversion)
+        image = image.convertToFormat(QImage::Format_RGBA8888);
+
+    // The image provided by the backingstore may have a stride larger than width * 4, for
+    // instance on platforms that manually implement client-side decorations.
+    static const int bytesPerPixel = 4;
+    const int strideInPixels = image.bytesPerLine() / bytesPerPixel;
+    const bool hasUnpackRowLength = !ctx->isOpenGLES() || ctx->format().majorVersion() >= 3;
+
+    QOpenGLFunctions *funcs = ctx->functions();
+
+    if (hasUnpackRowLength) {
+        funcs->glPixelStorei(GL_UNPACK_ROW_LENGTH, strideInPixels);
+    } else if (strideInPixels != image.width()) {
+        // No UNPACK_ROW_LENGTH on ES 2.0 and yet we would need it. This case is typically
+        // hit with QtWayland which is rarely used in combination with a ES2.0-only GL
+        // implementation.  Therefore, accept the performance hit and do a copy.
+        image = image.copy();
+    }
+
+    if (resized) {
+        if (textureId)
+            funcs->glDeleteTextures(1, &textureId);
+        funcs->glGenTextures(1, &textureId);
+        funcs->glBindTexture(GL_TEXTURE_2D, textureId);
+        if (!ctx->isOpenGLES() || ctx->format().majorVersion() >= 3) {
+            funcs->glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_BASE_LEVEL, 0);
+            funcs->glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAX_LEVEL, 0);
+        }
+        funcs->glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+        funcs->glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+        funcs->glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+        funcs->glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
+
+        funcs->glTexImage2D(GL_TEXTURE_2D, 0, internalFormat, imageSize.width(), imageSize.height(), 0, GL_RGBA, pixelType,
+                            const_cast<uchar*>(image.constBits()));
+    } else {
+        funcs->glBindTexture(GL_TEXTURE_2D, textureId);
+        QRect imageRect = image.rect();
+        QRect rect = dirtyRegion.boundingRect() & imageRect;
+
+        if (hasUnpackRowLength) {
+            funcs->glTexSubImage2D(GL_TEXTURE_2D, 0, rect.x(), rect.y(), rect.width(), rect.height(), GL_RGBA, pixelType,
+                                   image.constScanLine(rect.y()) + rect.x() * bytesPerPixel);
+        } else {
+            // if the rect is wide enough it's cheaper to just
+            // extend it instead of doing an image copy
+            if (rect.width() >= imageRect.width() / 2) {
+                rect.setX(0);
+                rect.setWidth(imageRect.width());
+            }
+
+            // if the sub-rect is full-width we can pass the image data directly to
+            // OpenGL instead of copying, since there's no gap between scanlines
+
+            if (rect.width() == imageRect.width()) {
+                funcs->glTexSubImage2D(GL_TEXTURE_2D, 0, 0, rect.y(), rect.width(), rect.height(), GL_RGBA, pixelType,
+                                       image.constScanLine(rect.y()));
+            } else {
+                funcs->glTexSubImage2D(GL_TEXTURE_2D, 0, rect.x(), rect.y(), rect.width(), rect.height(), GL_RGBA, pixelType,
+                                       image.copy(rect).constBits());
+            }
+        }
+    }
+
+    if (hasUnpackRowLength)
+        funcs->glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
+
+    return textureId;
+}
+
+#endif // QT_NO_OPENGL
+
+QT_END_NAMESPACE