OpenGL: Add code generator for OpenGL enabler classes

This patch provides a code generator that can be executed offline
to generate a few classes for enhancing Qt's support for OpenGL.
The generated code effectively provides all the benefits of GLEW
in its multi-context form but for all platforms and even for ES2.

The code generator takes as input the official Khronos gl.spec
specification and gl.tm typemap files. These provide all of the
information required to create the OpenGL Desktop related classes.
The classes for ES2 are hand-crafted as no similar spec files have
been published.

The generated code supports all OpenGL extensions listed in the
Khronos registry for both Desktop OpenGL and ES 2.

There is a helper factory class generated which are used by
QOpenGLContext::versionFunctions().

This allows code like the following to be written:

QOpenGLFunctions_3_3_Core* m_funcs = 0;
m_funcs = m_context->versionFunctions<QOpenGLFunctions_3_3_Core>();
if (!m_funcs) {
    qWarning() << "Could not obtain required OpenGL context version";
    exit(1);
}

if (!m_funcs->initializeOpenGLFunctions()) {
    qWarning() << "Failed to resolve entry points";
    exit(2);
}

// Get an extension object
QOpenGLExtension_ARB_draw_buffers* ext = 0;
if (m_context->hasExtension("GL_ARB_draw_buffers")) {
    ext = new QOpenGLExtension_ARB_draw_buffers();
    ext->initializeOpenGLFunctions(m_context);
}

Such usage will allow much easier and rigorous use of features in
modern OpenGL and extensions both in Qt itself and by users of Qt.

Follow-up patches will import the generated files and then use
these to reinstate OpenGL geometry shaders, add tessellation
shaders, and other OpenGL constructs.

Change-Id: Id0172e8aa1fd57eb4e6979a96d10fb5a34826426
Reviewed-by: Samuel Rødal <samuel.rodal@digia.com>
Reviewed-by: James Turner <james.turner@kdab.com>

1 files changed, 307 insertions, 0 deletions

diff --git a/util/glgen/specparser.cpp b/util/glgen/specparser.cpp
new file mode 100644
index 0000000000..514a700644
--- /dev/null
+++ b/util/glgen/specparser.cpp
@@ -0,0 +1,307 @@
+/***************************************************************************
+**
+** Copyright (C) 2013 Klaralvdalens Datakonsult AB (KDAB)
+** Contact: http://www.qt-project.org/legal
+**
+** This file is part of the utilities 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 Digia.  For licensing terms and
+** conditions see http://qt.digia.com/licensing.  For further information
+** use the contact form at http://qt.digia.com/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 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, Digia gives you certain additional
+** rights.  These rights are described in the Digia 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.
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "specparser.h"
+
+#include <QDebug>
+#include <QFile>
+#include <QRegExp>
+#include <QStringList>
+#include <QTextStream>
+
+#ifdef SPECPARSER_DEBUG
+#define qSpecParserDebug qDebug
+#else
+#define qSpecParserDebug QT_NO_QDEBUG_MACRO
+#endif
+
+SpecParser::SpecParser()
+{
+}
+
+void SpecParser::parse()
+{
+    // Get the mapping form generic types to specific types suitable for use in C-headers
+    if (!parseTypeMap())
+        return;
+
+    // Open up a stream on the actual OpenGL function spec file
+    QFile file(m_specFileName);
+    if (!file.open(QIODevice::ReadOnly | QIODevice::Text)) {
+        qWarning() << "Failed to open spec file:" << m_specFileName << "Aborting";
+        return;
+    }
+
+    QTextStream stream(&file);
+
+    // Extract the info that we need
+    parseFunctions(stream);
+}
+
+bool SpecParser::parseTypeMap()
+{
+    QFile file(m_typeMapFileName);
+    if (!file.open(QIODevice::ReadOnly | QIODevice::Text)) {
+        qWarning() << "Failed to open spec file:" << m_specFileName << "Aborting";
+        return false;
+    }
+
+    QTextStream stream(&file);
+
+    static QRegExp typeMapRegExp("([^,]+)\\W+([^,]+)");
+
+    while (!stream.atEnd()) {
+        QString line = stream.readLine();
+
+        if (line.startsWith(QStringLiteral("#")))
+            continue;
+
+        if (typeMapRegExp.indexIn(line) != -1) {
+            QString key = typeMapRegExp.cap(1).simplified();
+            QString value = typeMapRegExp.cap(2).simplified();
+
+            // Special case for void
+            if (value == QStringLiteral("*"))
+                value = QStringLiteral("void");
+
+            m_typeMap.insert(key, value);
+            qSpecParserDebug() << "Found type mapping from" << key << "=>" << value;
+        }
+    }
+
+    return true;
+}
+
+void SpecParser::parseEnums()
+{
+}
+
+void SpecParser::parseFunctions(QTextStream &stream)
+{
+    static QRegExp functionRegExp("^(\\w+)\\(.*\\)");
+    static QRegExp returnRegExp("^\\treturn\\s+(\\S+)");
+    static QRegExp argumentRegExp("param\\s+(\\S+)\\s+(\\S+) (\\S+) (\\S+)");
+    static QRegExp versionRegExp("^\\tversion\\s+(\\S+)");
+    static QRegExp deprecatedRegExp("^\\tdeprecated\\s+(\\S+)");
+    static QRegExp categoryRegExp("^\\tcategory\\s+(\\S+)");
+    static QRegExp categoryVersionRegExp("VERSION_(\\d)_(\\d)");
+    static QRegExp extToCoreVersionRegExp("passthru:\\s/\\*\\sOpenGL\\s(\\d)\\.(\\d)\\s.*\\sextensions:");
+    static QRegExp extToCoreRegExp("passthru:\\s/\\*\\s(ARB_\\S*)\\s.*\\*/");
+
+    Function currentFunction;
+    VersionProfile currentVersionProfile;
+    QString currentCategory;
+    bool haveVersionInfo = false;
+    bool acceptCurrentFunctionInCore = false;
+    bool acceptCurrentFunctionInExtension = false;
+
+    QHash<QString, Version> extensionsNowInCore;
+    Version extToCoreCurrentVersion;
+    int functionCount = 0;
+
+    QSet<Version> versions;
+
+    while (!stream.atEnd()) {
+        QString line = stream.readLine();
+        if (line.startsWith("#"))
+            continue;
+
+        if (functionRegExp.indexIn(line) != -1) {
+
+            if (!currentFunction.name.isEmpty()) {
+
+                // NB - Special handling!
+                // Versions 4.2 and 4.3 (and probably newer) add functionality by
+                // subsuming extensions such as ARB_texture_storage. However, some extensions
+                // also include functions to interact with the EXT_direct_state_access
+                // extension. These functions should be added to the DSA extension rather
+                // than the core functionality. The core will already contain non-DSA
+                // versions of these functions.
+                if (acceptCurrentFunctionInCore && currentFunction.name.endsWith(QStringLiteral("EXT"))) {
+                    acceptCurrentFunctionInCore = false;
+                    acceptCurrentFunctionInExtension = true;
+                    currentCategory = QStringLiteral("EXT_direct_state_access");
+                }
+
+                // Finish off previous function (if any) by inserting it into the core
+                // functionality or extension functionality (or both)
+                if (acceptCurrentFunctionInCore) {
+                    m_functions.insert(currentVersionProfile, currentFunction);
+                    versions.insert(currentVersionProfile.version);
+                }
+
+                if (acceptCurrentFunctionInExtension)
+                    m_extensionFunctions.insert(currentCategory, currentFunction);
+            }
+
+            // Start a new function
+            ++functionCount;
+            haveVersionInfo = false;
+            acceptCurrentFunctionInCore = true;
+            acceptCurrentFunctionInExtension = false;
+            currentCategory = QString();
+            currentFunction = Function();
+
+            // We assume a core function unless we find a deprecated flag (see below)
+            currentVersionProfile = VersionProfile();
+            currentVersionProfile.profile = VersionProfile::CoreProfile;
+
+            // Extract the function name
+            QString functionName = functionRegExp.cap(1);
+            currentFunction.name = functionName;
+            qSpecParserDebug() << "Found function:" << functionName;
+
+        } else if (argumentRegExp.indexIn(line) != -1) {
+            // Extract info about this function argument
+            Argument arg;
+            arg.name = argumentRegExp.cap(1);
+
+            QString type = argumentRegExp.cap(2); // Lookup in type map
+            arg.type = m_typeMap.value(type);
+
+            QString direction = argumentRegExp.cap(3);
+            if (direction == QStringLiteral("in")) {
+                arg.direction = Argument::In;
+            } else if (direction == QStringLiteral("out")) {
+                arg.direction = Argument::Out;
+            } else {
+                qWarning() << "Invalid argument direction found:" << direction;
+                acceptCurrentFunctionInCore = false;
+            }
+
+            QString mode = argumentRegExp.cap(4);
+            if (mode == QStringLiteral("value")) {
+                arg.mode = Argument::Value;
+            } else if (mode == QStringLiteral("array")) {
+                arg.mode = Argument::Array;
+            } else if (mode == QStringLiteral("reference")) {
+                arg.mode = Argument::Reference;
+            } else {
+                qWarning() << "Invalid argument mode found:" << mode;
+                acceptCurrentFunctionInCore = false;
+            }
+
+            qSpecParserDebug() << "    argument:" << arg.type << arg.name;
+            currentFunction.arguments.append(arg);
+
+        } else if (returnRegExp.indexIn(line) != -1) {
+            // Lookup the return type from the typemap
+            QString returnTypeKey = returnRegExp.cap(1).simplified();
+            if (!m_typeMap.contains(returnTypeKey)) {
+                qWarning() << "Unknown return type found:" << returnTypeKey;
+                acceptCurrentFunctionInCore = false;
+            }
+            QString returnType = m_typeMap.value(returnTypeKey);
+            qSpecParserDebug() << "    return type:" << returnType;
+            currentFunction.returnType = returnType;
+
+        } else if (versionRegExp.indexIn(line) != -1 && !haveVersionInfo) { // Only use version line if no other source
+            // Extract the OpenGL version in which this function was introduced
+            QString version = versionRegExp.cap(1);
+            qSpecParserDebug() << "    version:" << version;
+            QStringList parts = version.split(QLatin1Char('.'));
+            if (parts.size() != 2) {
+                qWarning() << "Found invalid version number";
+                continue;
+            }
+            int majorVersion = parts.first().toInt();
+            int minorVersion = parts.last().toInt();
+            Version v;
+            v.major = majorVersion;
+            v.minor = minorVersion;
+            currentVersionProfile.version = v;
+
+        } else if (deprecatedRegExp.indexIn(line) != -1) {
+            // Extract the OpenGL version in which this function was deprecated.
+            // If it is OpenGL 3.1 then it must be a compatibility profile function
+            QString deprecatedVersion = deprecatedRegExp.cap(1).simplified();
+            if (deprecatedVersion == QStringLiteral("3.1"))
+                currentVersionProfile.profile = VersionProfile::CompatibilityProfile;
+
+        } else if (categoryRegExp.indexIn(line) != -1) {
+            // Extract the category for this function
+            QString category = categoryRegExp.cap(1).simplified();
+            qSpecParserDebug() << "    category:" << category;
+
+            if (categoryVersionRegExp.indexIn(category) != -1) {
+                // Use the version info in the category in preference to the version
+                // entry as this is more applicable and consistent
+                int majorVersion = categoryVersionRegExp.cap(1).toInt();
+                int minorVersion = categoryVersionRegExp.cap(2).toInt();
+
+                Version v;
+                v.major = majorVersion;
+                v.minor = minorVersion;
+                currentVersionProfile.version = v;
+                haveVersionInfo = true;
+
+            } else {
+                // Make a note of the extension name and tag this function as being part of an extension
+                qSpecParserDebug() << "Found category =" << category;
+                currentCategory = category;
+                acceptCurrentFunctionInExtension = true;
+
+                // See if this category (extension) is in our set of extensions that
+                // have now been folded into the core feature set
+                if (extensionsNowInCore.contains(category)) {
+                    currentVersionProfile.version = extensionsNowInCore.value(category);
+                    haveVersionInfo = true;
+                } else {
+                    acceptCurrentFunctionInCore = false;
+                }
+            }
+
+        } else if (extToCoreVersionRegExp.indexIn(line) != -1) {
+            qSpecParserDebug() << line;
+            int majorVersion = extToCoreVersionRegExp.cap(1).toInt();
+            int minorVersion = extToCoreVersionRegExp.cap(2).toInt();
+            extToCoreCurrentVersion.major = majorVersion;
+            extToCoreCurrentVersion.minor = minorVersion;
+
+        } else if (extToCoreRegExp.indexIn(line) != -1) {
+            QString extension = extToCoreRegExp.cap(1);
+            extensionsNowInCore.insert(extension, extToCoreCurrentVersion);
+        }
+    }
+
+    m_versions = versions.toList();
+    qSort(m_versions);
+}