QtPlatformSupport: A helper library for platform plugins

QtPlatformSupport is a static library. Platform plugins are meant to
link against this library to pull in dependencies such as fontengines
and convenience functions for finding the right GL configs. The linker
will only pull in the symbols used, so the size of the library doesn't
really matter

1 files changed, 306 insertions, 0 deletions

diff --git a/src/platformsupport/eglconvenience/qeglconvenience.cpp b/src/platformsupport/eglconvenience/qeglconvenience.cpp
new file mode 100644
index 0000000000..a9973b642a
--- /dev/null
+++ b/src/platformsupport/eglconvenience/qeglconvenience.cpp
@@ -0,0 +1,306 @@
+/****************************************************************************
+**
+** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
+** All rights reserved.
+** Contact: Nokia Corporation (qt-info@nokia.com)
+**
+** This file is part of the plugins of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** GNU Lesser General Public License Usage
+** This file may be used under the terms of the GNU Lesser General Public
+** License version 2.1 as published by the Free Software Foundation and
+** appearing in the file LICENSE.LGPL included in the packaging of this
+** file. Please review the following information to ensure the GNU Lesser
+** General Public License version 2.1 requirements will be met:
+** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Nokia gives you certain additional
+** rights. These rights are described in the Nokia Qt LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU General
+** Public License version 3.0 as published by the Free Software Foundation
+** and appearing in the file LICENSE.GPL included in the packaging of this
+** file. Please review the following information to ensure the GNU General
+** Public License version 3.0 requirements will be met:
+** http://www.gnu.org/copyleft/gpl.html.
+**
+** Other Usage
+** Alternatively, this file may be used in accordance with the terms and
+** conditions contained in a signed written agreement between you and Nokia.
+**
+**
+**
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include <QByteArray>
+
+#include "qeglconvenience_p.h"
+
+QT_BEGIN_NAMESPACE
+
+QVector<EGLint> q_createConfigAttributesFromFormat(const QGuiGLFormat &format)
+{
+    int redSize     = format.redBufferSize();
+    int greenSize   = format.greenBufferSize();
+    int blueSize    = format.blueBufferSize();
+    int alphaSize   = format.alphaBufferSize();
+    int depthSize   = format.depthBufferSize();
+    int stencilSize = format.stencilBufferSize();
+    int sampleCount = format.samples();
+
+    // We want to make sure 16-bit configs are chosen over 32-bit configs as they will provide
+    // the best performance. The EGL config selection algorithm is a bit stange in this regard:
+    // The selection criteria for EGL_BUFFER_SIZE is "AtLeast", so we can't use it to discard
+    // 32-bit configs completely from the selection. So it then comes to the sorting algorithm.
+    // The red/green/blue sizes have a sort priority of 3, so they are sorted by first. The sort
+    // order is special and described as "by larger _total_ number of color bits.". So EGL will
+    // put 32-bit configs in the list before the 16-bit configs. However, the spec also goes on
+    // to say "If the requested number of bits in attrib_list for a particular component is 0,
+    // then the number of bits for that component is not considered". This part of the spec also
+    // seems to imply that setting the red/green/blue bits to zero means none of the components
+    // are considered and EGL disregards the entire sorting rule. It then looks to the next
+    // highest priority rule, which is EGL_BUFFER_SIZE. Despite the selection criteria being
+    // "AtLeast" for EGL_BUFFER_SIZE, it's sort order is "smaller" meaning 16-bit configs are
+    // put in the list before 32-bit configs. So, to make sure 16-bit is preffered over 32-bit,
+    // we must set the red/green/blue sizes to zero. This has an unfortunate consequence that
+    // if the application sets the red/green/blue size to 5/6/5 on the QGuiGLFormat,
+    // they will probably get a 32-bit config, even when there's an RGB565 config available.
+
+//    // Now normalize the values so -1 becomes 0
+//    redSize   = redSize   > 0 ? redSize   : 0;
+//    greenSize = greenSize > 0 ? greenSize : 0;
+//    blueSize  = blueSize  > 0 ? blueSize  : 0;
+//    alphaSize = alphaSize > 0 ? alphaSize : 0;
+//    depthSize = depthSize > 0 ? depthSize : 0;
+//    stencilSize = stencilSize > 0 ? stencilSize : 0;
+//    sampleCount = sampleCount > 0 ? sampleCount : 0;
+
+    QVector<EGLint> configAttributes;
+
+    configAttributes.append(EGL_RED_SIZE);
+    configAttributes.append(redSize);
+
+    configAttributes.append(EGL_GREEN_SIZE);
+    configAttributes.append(greenSize);
+
+    configAttributes.append(EGL_BLUE_SIZE);
+    configAttributes.append(blueSize);
+
+    configAttributes.append(EGL_ALPHA_SIZE);
+    configAttributes.append(alphaSize);
+
+    configAttributes.append(EGL_DEPTH_SIZE);
+    configAttributes.append(depthSize);
+
+    configAttributes.append(EGL_STENCIL_SIZE);
+    configAttributes.append(stencilSize);
+
+    configAttributes.append(EGL_SAMPLES);
+    configAttributes.append(sampleCount);
+
+    configAttributes.append(EGL_SAMPLE_BUFFERS);
+    configAttributes.append(sampleCount? 1:0);
+
+    return configAttributes;
+}
+
+bool q_reduceConfigAttributes(QVector<EGLint> *configAttributes)
+{
+    int i = -1;
+    // Reduce the complexity of a configuration request to ask for less
+    // because the previous request did not result in success.  Returns
+    // true if the complexity was reduced, or false if no further
+    // reductions in complexity are possible.
+
+    i = configAttributes->indexOf(EGL_SWAP_BEHAVIOR);
+    if (i >= 0) {
+        configAttributes->remove(i,2);
+    }
+
+#ifdef EGL_VG_ALPHA_FORMAT_PRE_BIT
+    // For OpenVG, we sometimes try to create a surface using a pre-multiplied format. If we can't
+    // find a config which supports pre-multiplied formats, remove the flag on the surface type:
+
+    i = configAttributes->indexOf(EGL_SURFACE_TYPE);
+    if (i >= 0) {
+        EGLint surfaceType = configAttributes->at(i +1);
+        if (surfaceType & EGL_VG_ALPHA_FORMAT_PRE_BIT) {
+            surfaceType ^= EGL_VG_ALPHA_FORMAT_PRE_BIT;
+            configAttributes->replace(i+1,surfaceType);
+            return true;
+        }
+    }
+#endif
+
+    // EGL chooses configs with the highest color depth over
+    // those with smaller (but faster) lower color depths. One
+    // way around this is to set EGL_BUFFER_SIZE to 16, which
+    // trumps the others. Of course, there may not be a 16-bit
+    // config available, so it's the first restraint we remove.
+    i = configAttributes->indexOf(EGL_BUFFER_SIZE);
+    if (i >= 0) {
+        if (configAttributes->at(i+1) == 16) {
+            configAttributes->remove(i,2);
+            return true;
+        }
+    }
+
+    i = configAttributes->indexOf(EGL_SAMPLE_BUFFERS);
+    if (i >= 0) {
+        configAttributes->remove(i,2);
+        i = configAttributes->indexOf(EGL_SAMPLES);
+        if (i >= 0) {
+            configAttributes->remove(i,2);
+        }
+        return true;
+    }
+
+    i = configAttributes->indexOf(EGL_ALPHA_SIZE);
+    if (i >= 0) {
+        configAttributes->remove(i,2);
+#if defined(EGL_BIND_TO_TEXTURE_RGBA) && defined(EGL_BIND_TO_TEXTURE_RGB)
+        i = configAttributes->indexOf(EGL_BIND_TO_TEXTURE_RGBA);
+        if (i >= 0) {
+            configAttributes->replace(i,EGL_BIND_TO_TEXTURE_RGB);
+            configAttributes->replace(i+1,TRUE);
+
+        }
+#endif
+        return true;
+    }
+
+    i = configAttributes->indexOf(EGL_STENCIL_SIZE);
+    if (i >= 0) {
+        configAttributes->remove(i,2);
+        return true;
+    }
+    i = configAttributes->indexOf(EGL_DEPTH_SIZE);
+    if (i >= 0) {
+        configAttributes->remove(i,2);
+        return true;
+    }
+#ifdef EGL_BIND_TO_TEXTURE_RGB
+    i = configAttributes->indexOf(EGL_BIND_TO_TEXTURE_RGB);
+    if (i >= 0) {
+        configAttributes->remove(i,2);
+        return true;
+    }
+#endif
+
+    return false;
+}
+
+EGLConfig q_configFromGLFormat(EGLDisplay display, const QGuiGLFormat &format, bool highestPixelFormat, int surfaceType)
+{
+    EGLConfig cfg = 0;
+    QVector<EGLint> configureAttributes = q_createConfigAttributesFromFormat(format);
+    configureAttributes.append(EGL_SURFACE_TYPE); //we only support eglconfigs for windows for now
+    configureAttributes.append(surfaceType);
+
+    configureAttributes.append(EGL_RENDERABLE_TYPE);
+    configureAttributes.append(EGL_OPENGL_ES2_BIT);
+    configureAttributes.append(EGL_NONE);
+
+    do {
+        // Get the number of matching configurations for this set of properties.
+        EGLint matching = 0;
+        if (!eglChooseConfig(display, configureAttributes.constData(), 0, 0, &matching) || !matching)
+            continue;
+
+        // If we want the best pixel format, then return the first
+        // matching configuration.
+        if (highestPixelFormat) {
+            eglChooseConfig(display, configureAttributes.constData(), &cfg, 1, &matching);
+            if (matching < 1)
+                continue;
+            return cfg;
+        }
+
+        // Fetch all of the matching configurations and find the
+        // first that matches the pixel format we wanted.
+        int i = configureAttributes.indexOf(EGL_RED_SIZE);
+        int confAttrRed = configureAttributes.at(i+1);
+        i = configureAttributes.indexOf(EGL_GREEN_SIZE);
+        int confAttrGreen = configureAttributes.at(i+1);
+        i = configureAttributes.indexOf(EGL_BLUE_SIZE);
+        int confAttrBlue = configureAttributes.at(i+1);
+        i = configureAttributes.indexOf(EGL_ALPHA_SIZE);
+        int confAttrAlpha = configureAttributes.at(i+1);
+
+        EGLint size = matching;
+        EGLConfig *configs = new EGLConfig [size];
+        eglChooseConfig(display, configureAttributes.constData(), configs, size, &matching);
+        for (EGLint index = 0; index < size; ++index) {
+            EGLint red, green, blue, alpha;
+            eglGetConfigAttrib(display, configs[index], EGL_RED_SIZE, &red);
+            eglGetConfigAttrib(display, configs[index], EGL_GREEN_SIZE, &green);
+            eglGetConfigAttrib(display, configs[index], EGL_BLUE_SIZE, &blue);
+            eglGetConfigAttrib(display, configs[index], EGL_ALPHA_SIZE, &alpha);
+            if (red == confAttrRed &&
+                    green == confAttrGreen &&
+                    blue == confAttrBlue &&
+                    (confAttrAlpha == 0 ||
+                     alpha == confAttrAlpha)) {
+                cfg = configs[index];
+                delete [] configs;
+                return cfg;
+            }
+        }
+        delete [] configs;
+    } while (q_reduceConfigAttributes(&configureAttributes));
+    qWarning("Cant find EGLConfig, returning null config");
+    return 0;
+}
+
+QGuiGLFormat q_glFormatFromConfig(EGLDisplay display, const EGLConfig config)
+{
+    QGuiGLFormat format;
+    EGLint redSize     = 0;
+    EGLint greenSize   = 0;
+    EGLint blueSize    = 0;
+    EGLint alphaSize   = 0;
+    EGLint depthSize   = 0;
+    EGLint stencilSize = 0;
+    EGLint sampleCount = 0;
+
+    eglGetConfigAttrib(display, config, EGL_RED_SIZE,     &redSize);
+    eglGetConfigAttrib(display, config, EGL_GREEN_SIZE,   &greenSize);
+    eglGetConfigAttrib(display, config, EGL_BLUE_SIZE,    &blueSize);
+    eglGetConfigAttrib(display, config, EGL_ALPHA_SIZE,   &alphaSize);
+    eglGetConfigAttrib(display, config, EGL_DEPTH_SIZE,   &depthSize);
+    eglGetConfigAttrib(display, config, EGL_STENCIL_SIZE, &stencilSize);
+    eglGetConfigAttrib(display, config, EGL_SAMPLES,      &sampleCount);
+
+    format.setRedBufferSize(redSize);
+    format.setGreenBufferSize(greenSize);
+    format.setBlueBufferSize(blueSize);
+    format.setAlphaBufferSize(alphaSize);
+    format.setDepthBufferSize(depthSize);
+    format.setStencilBufferSize(stencilSize);
+    format.setSamples(sampleCount);
+    format.setStereo(false);         // EGL doesn't support stereo buffers
+
+    // Clear the EGL error state because some of the above may
+    // have errored out because the attribute is not applicable
+    // to the surface type.  Such errors don't matter.
+    eglGetError();
+
+    return format;
+}
+
+bool q_hasEglExtension(EGLDisplay display, const char* extensionName)
+{
+    QList<QByteArray> extensions =
+        QByteArray(reinterpret_cast<const char *>
+            (eglQueryString(display, EGL_EXTENSIONS))).split(' ');
+    return extensions.contains(extensionName);
+}
+
+QT_END_NAMESPACE