From af3d842e6096c3ecd9da8ea2964b5882852cb79e Mon Sep 17 00:00:00 2001
From: David Rowe <david@ctrlaltstudio.com>
Date: Thu, 28 Jan 2016 15:22:42 +1300
Subject: [PATCH] Warn user if OpenGL version is too low (< 4.1)

---
 interface/src/OpenGLInfo.cpp | 60 ++++++++++++++++++++++++++++++++++++
 interface/src/OpenGLInfo.h   | 25 +++++++++++++++
 interface/src/main.cpp       | 13 ++++++++
 3 files changed, 98 insertions(+)
 create mode 100644 interface/src/OpenGLInfo.cpp
 create mode 100644 interface/src/OpenGLInfo.h

diff --git a/interface/src/OpenGLInfo.cpp b/interface/src/OpenGLInfo.cpp
new file mode 100644
index 0000000000..b61863c1bf
--- /dev/null
+++ b/interface/src/OpenGLInfo.cpp
@@ -0,0 +1,60 @@
+//
+//  OpenGLInfo.cpp
+//  interface/src
+//
+//  Created by David Rowe on 28 Jan 2016.
+//  Copyright 2016 High Fidelity, Inc.
+//
+//  Distributed under the Apache License, Version 2.0.
+//  See the accompanying file LICENSE or http://www.apache.org/licenses/LICENSE-2.0.html
+//
+
+#include "OpenGLInfo.h"
+
+#include <QMessageBox>
+#include <QRegularExpression>
+
+#include "GLCanvas.h"
+
+OpenGLInfo::OpenGLInfo(int& argc, char** argv) :
+    QApplication(argc, argv)
+{
+}
+
+bool OpenGLInfo::isValidVersion() {
+    bool valid = true;
+
+    // Retrieve OpenGL version
+    GLCanvas* glCanvas = new GLCanvas();
+    glCanvas->initializeGL();
+    QString glVersion = QString((const char*)glGetString(GL_VERSION));
+    delete glCanvas;
+
+    // Compare against minimum
+    // The GL_VERSION string begins with a version number in one of these forms:
+    // - major_number.minor_number 
+    // - major_number.minor_number.release_number
+    // Reference: https://www.opengl.org/sdk/docs/man/docbook4/xhtml/glGetString.xml
+    const int MINIMUM_OPENGL_MAJOR_VERSION = 4;
+    const int MINIMUM_OPENGL_MINOR_VERSION = 1;
+    QStringList versionParts = glVersion.split(QRegularExpression("[\\.\\s]"));
+    int majorNumber = versionParts[0].toInt();
+    int minorNumber = versionParts[1].toInt();
+    valid = (majorNumber > MINIMUM_OPENGL_MAJOR_VERSION
+        || (majorNumber == MINIMUM_OPENGL_MAJOR_VERSION && minorNumber >= MINIMUM_OPENGL_MINOR_VERSION));
+
+    // Prompt user if below minimum
+    if (!valid) {
+        QMessageBox messageBox;
+        messageBox.setWindowTitle("OpenGL Version Too Low");
+        messageBox.setIcon(QMessageBox::Warning);
+        messageBox.setText(QString().sprintf("Your OpenGL version of %i.%i is lower than the minimum of %i.%i.",
+            majorNumber, minorNumber, MINIMUM_OPENGL_MAJOR_VERSION, MINIMUM_OPENGL_MINOR_VERSION));
+        messageBox.setInformativeText("Press OK to exit; Ignore to continue.");
+        messageBox.setStandardButtons(QMessageBox::Ok | QMessageBox::Ignore);
+        messageBox.setDefaultButton(QMessageBox::Ok);
+        valid = messageBox.exec() == QMessageBox::Ignore;
+    }
+
+    return valid;
+}
diff --git a/interface/src/OpenGLInfo.h b/interface/src/OpenGLInfo.h
new file mode 100644
index 0000000000..8df44c72b1
--- /dev/null
+++ b/interface/src/OpenGLInfo.h
@@ -0,0 +1,25 @@
+//
+//  OpenGLInfo.h
+//  interface/src
+//
+//  Created by David Rowe on 28 Jan 2016.
+//  Copyright 2016 High Fidelity, Inc.
+//
+//  Distributed under the Apache License, Version 2.0.
+//  See the accompanying file LICENSE or http://www.apache.org/licenses/LICENSE-2.0.html
+//
+
+#ifndef hifi_OpenGLInfo_h
+#define hifi_OpenGLInfo_h
+
+#include <QApplication>
+
+class OpenGLInfo : public QApplication {
+
+public:
+    OpenGLInfo(int& argc, char** argv);
+
+    static bool isValidVersion();
+};
+
+#endif // hifi_OpenGLInfo_h
diff --git a/interface/src/main.cpp b/interface/src/main.cpp
index 15da88023b..db02994a19 100644
--- a/interface/src/main.cpp
+++ b/interface/src/main.cpp
@@ -22,6 +22,7 @@
 #include "AddressManager.h"
 #include "Application.h"
 #include "InterfaceLogging.h"
+#include "OpenGLInfo.h"
 #include "MainWindow.h"
 
 int main(int argc, const char* argv[]) {
@@ -83,6 +84,17 @@ int main(int argc, const char* argv[]) {
 #endif
     }
 
+    // Check OpenGL version.
+    // This is done separately from the main Application so that start-up and shut-down logic within the main Application is
+    // not made more complicated than it already is.
+    {
+        OpenGLInfo openGLInfo(argc, const_cast<char**>(argv));
+        if (!openGLInfo.isValidVersion()) {
+            qCDebug(interfaceapp, "Early exit due to OpenGL version.");
+            return 0;
+        }
+    }
+
     QElapsedTimer startupTime;
     startupTime.start();
 
@@ -96,6 +108,7 @@ int main(int argc, const char* argv[]) {
         usecTimestampNowForceClockSkew(clockSkew);
         qCDebug(interfaceapp, "clockSkewOption=%s clockSkew=%d", clockSkewOption, clockSkew);
     }
+
     // Oculus initialization MUST PRECEDE OpenGL context creation.
     // The nature of the Application constructor means this has to be either here,
     // or in the main window ctor, before GL startup.