Improve OpenGL robustness; refactor glscope.cpp; fix #184

If the graphic system claims to support SL version 150 but this fails,
fall back automatically to legacy version 120. If this also fails,
show the hint to use the command line option '--useGLES'
to switch from OpenGL to OpenGLES (OpenGL for Embedded Systems),
which cannot be done automatically.

Signed-off-by: Martin <Ho-Ro@users.noreply.github.com>

Author: Ho-Ro

README.md

@@ -9,10 +9,6 @@
 OpenHantek6022 is a free software for **Hantek DSO6022** USB digital signal oscilloscopes that is actively developed on
 [github.com/OpenHantek/OpenHantek6022](https://github.com/OpenHantek/OpenHantek6022) - but only for Hantek 6022BE/BL and compatible scopes (Voltcraft, Darkwire, Protek, Acetech, etc.).
 
-The program was initially developed by [David Gräff and others](https://github.com/OpenHantek/openhantek/graphs/contributors)
-on [github.com/OpenHantek/openhantek](https://github.com/OpenHantek/openhantek),
-but David [stopped maintaining](https://github.com/OpenHantek/openhantek/issues/277) the programm in December 2018. 
-
 <p><img alt="Image of main window on linux" width="100%" src="docs/images/screenshot_mainwindow.png"></p>
 
 #### Content
@@ -29,6 +25,7 @@ but David [stopped maintaining](https://github.com/OpenHantek/openhantek/issues/
 * [Contribute](#contribute)
 * [Other DSO open source software](#other-dso-open-source-software)
 * [Other related software](#other-related-software)
+* [History](#history)
 
 ## About OpenHantek6022
 * Supported devices:
@@ -69,7 +66,7 @@ but David [stopped maintaining](https://github.com/OpenHantek/openhantek/issues/
 * Histogram function for voltage channels on right screen margin.
 * A [zoom view](docs/images/screenshot_mainwindow_with_zoom.png) with a freely selectable range.
 * Cursor measurement function for voltage, time, amplitude and frequency.
-* Export of the graphs to CSV, JPG, PNG file or to the printer.
+* Export of the graphs to JPG, PNG or PDF file or to the printer; data export as CSV or JSON. 
 * Freely configurable colors.
 * Automatic adaption of iconset for light and [dark themes](docs/images/screenshot_mainwindow_dark.png).
 * The dock views on the main window can be [customized](https://github.com/OpenHantek/OpenHantek6022/issues/161#issuecomment-799597664) by dragging them around and stacking them.
@@ -127,15 +124,21 @@ On a Linux system start the program via the menu entry *OpenHantek (Digital Stor
 
 You can explore the look and feel of OpenHantek6022 without the need for real scope hardware by running it from the command line as: `OpenHantek --demoMode`.
 
-OpenHantek6022 runs also on legacy HW/SW that supports at least *OpenGL* 2.1+ or *OpenGL ES* 1.2+.
-OpenGL is preferred, select *OpenGL ES* by starting OpenHantek
-from the command line like this: `OpenHantek --useGLES`.
+### OpenGL support
+OpenHantek6022 uses the *OpenGL* graphics library to display the data. It requires a graphics card that supports
+3D rendering and runs on legacy HW/SW that supports at least *OpenGL* 2.1+ or *OpenGL ES* 1.2+.
+*OpenGL* is selected by default, but if this does not work (i.e. the black scope window shows an error message
+or closes immediately after startup), you can choose the less resource-hungry *OpenGL ES* variant as a fallback
+by starting OpenHantek from the command line as follows: `OpenHantek -e` or `OpenHantek --useGLES`.
+
+Especially on Windows, this option may be necessary to use the program.
 
 The Raspberry Pi build uses OpenGL ES automatically, check also the [graphics driver setup](docs/build.md#raspberrypi).
 
+### USB access
 USB access for the device is required (unless using demo mode):
 * On Linux, you need to copy the file `utils/udev_rules/60-openhantek.rules` to `/etc/udev/rules.d/` or `/usr/lib/udev/rules.d/` and replug your device.
-If OpenHantek is installed from a *.deb or *.rpm package this file is installed automatically into `/usr/lib/udev/rules.d/`.
+If OpenHantek is installed from a `*.deb` or `*.rpm` package this file is installed automatically into `/usr/lib/udev/rules.d/`.
 
 ### Windows USB access
 * **The original Hantek driver for Windows doesn't work!**
@@ -179,3 +182,8 @@ We welcome any reported GitHub issue if you have a problem with this software. S
 
 ## Other related software
 * [HScope for Android](https://www.martinloren.com/hscope/) A one-channel basic version is available free of charge (with in-app purchases).
+
+## History
+The program was initially developed by [David Gräff and others](https://github.com/OpenHantek/openhantek/graphs/contributors)
+on [github.com/OpenHantek/openhantek](https://github.com/OpenHantek/openhantek),
+but David [stopped maintaining](https://github.com/OpenHantek/openhantek/issues/277) the programm in December 2018. 

openhantek/src/OH_BUILD.h

@@ -1,2 +1,2 @@
 // Do not edit, will be re-created at each commit!
-#define OH_BUILD "20210424 - commit 893"
+#define OH_BUILD "20210426 - commit 894"

openhantek/src/glscope.cpp

@@ -24,53 +24,35 @@
 #include "viewsettings.h"
 
 
-GlScope *GlScope::createNormal( DsoSettingsScope *scope, DsoSettingsView *view, QWidget *parent ) {
-    GlScope *s = new GlScope( scope, view, parent );
-    s->zoomed = false;
-    return s;
-}
-
-
-GlScope *GlScope::createZoomed( DsoSettingsScope *scope, DsoSettingsView *view, QWidget *parent ) {
-    GlScope *s = new GlScope( scope, view, parent );
-    s->zoomed = true;
-    return s;
-}
-
+unsigned GlScope::forceGLSLversion = 0; // static, can be set to 120 or 150 by GlScope::useOpenGLSLversion()
 
-void GlScope::useQSurfaceFormat( QSurfaceFormat::RenderableType t ) {
-    // QCoreApplication::setAttribute( Qt::AA_ShareOpenGLContexts, true ); // too late here, set early in main()
 
+// this static function will be called early from main to set up OpenGL
+void GlScope::useQSurfaceFormat( QSurfaceFormat::RenderableType rendering ) {
+    QCoreApplication::setAttribute( Qt::AA_ShareOpenGLContexts, true );
     // Prefer full desktop OpenGL without fixed pipeline
     QSurfaceFormat format;
-    // from time to time the next line can give a warning
-    format.setSamples( 4 ); // antialiasing gives warning with some HW, Qt & OpenGL versions.
+    format.setSamples( 4 ); // ignore antialiasing warning with some HW, Qt & OpenGL versions.
     format.setProfile( QSurfaceFormat::CoreProfile );
-    if ( t == QSurfaceFormat::OpenGLES ) {
-        // format.setVersion( 2, 0 );
-        format.setRenderableType( QSurfaceFormat::OpenGLES );
-        QCoreApplication::setAttribute( Qt::AA_UseOpenGLES, true );
-    } else {
-        // format.setVersion( 3, 2 );
-        format.setRenderableType( QSurfaceFormat::OpenGL );
-    }
+    format.setRenderableType( rendering );
+    QCoreApplication::setAttribute( Qt::AA_UseOpenGLES, rendering == QSurfaceFormat::OpenGLES );
     QSurfaceFormat::setDefaultFormat( format );
 }
 
 
 GlScope::GlScope( DsoSettingsScope *scope, DsoSettingsView *view, QWidget *parent )
     : QOpenGLWidget( parent ), scope( scope ), view( view ) {
     // get OpenGL version to define appropriate OpenGLSL version
-    // reason:
-    // some not so new intel graphic driver report a very conservative version
-    // e.g. debian buster -> "2.1 Mesa 18.3.4"
+    // reason: some not so new intel graphic driver report a very conservative version
+    // even if they deliver OpenGL 4.x functions
+    // e.g. debian buster -> "2.1 Mesa 18.3.6"
     QOffscreenSurface surface;
     surface.create();
     QOpenGLContext context;
     context.create();
     context.makeCurrent( &surface );
-    QString glVersion = reinterpret_cast< const char * >( context.functions()->glGetString( GL_VERSION ) );
-    GLSLversion = glVersion >= "3.2" ? 150 : 120; // version string "3.2 xxxx" > "3.2" is true
+    OpenGLversion = reinterpret_cast< const char * >( context.functions()->glGetString( GL_VERSION ) );
+    GLSLversion = OpenGLversion >= "3.2" ? 150 : 120; // version string "3.2 xxxx" > "3.2" is true
     // qDebug() << "OpenGL version" << glVersion << GLSLversion;
     surface.destroy();
 
@@ -91,6 +73,20 @@ GlScope::~GlScope() { /* virtual destructor necessary */
 }
 
 
+GlScope *GlScope::createNormal( DsoSettingsScope *scope, DsoSettingsView *view, QWidget *parent ) {
+    GlScope *s = new GlScope( scope, view, parent );
+    s->zoomed = false;
+    return s;
+}
+
+
+GlScope *GlScope::createZoomed( DsoSettingsScope *scope, DsoSettingsView *view, QWidget *parent ) {
+    GlScope *s = new GlScope( scope, view, parent );
+    s->zoomed = true;
+    return s;
+}
+
+
 QPointF GlScope::posToPosition( QPointF pos ) {
     QPointF position( double( pos.x() - width() / 2 ) * DIVS_TIME / double( width() ),
                       double( height() / 2 - pos.y() ) * DIVS_VOLTAGE / double( height() ) );
@@ -275,8 +271,6 @@ void GlScope::paintEvent( QPaintEvent *event ) {
 }
 
 
-unsigned GlScope::forceGLSLversion = 0;
-
 void GlScope::initializeGL() {
     if ( !QOpenGLShaderProgram::hasOpenGLShaderPrograms( context() ) ) {
         errorMessage = tr( "System does not support OpenGL Shading Language (GLSL)" );
@@ -289,7 +283,7 @@ void GlScope::initializeGL() {
 
     auto program = std::unique_ptr< QOpenGLShaderProgram >( new QOpenGLShaderProgram( context() ) );
 
-    const char *vshaderES = R"(
+    const char *vertexShaderGLES = R"(
           #version 100
           attribute highp vec3 vertex;
           uniform mat4 matrix;
@@ -299,13 +293,8 @@ void GlScope::initializeGL() {
               gl_PointSize = 1.0;
           }
     )";
-    const char *fshaderES = R"(
-          #version 100
-          uniform highp vec4 colour;
-          void main() { gl_FragColor = colour; }
-    )";
 
-    const char *vshaderDesktop120 = R"(
+    const char *vertexShaderGLSL120 = R"(
           #version 120
           attribute highp vec3 vertex;
           uniform mat4 matrix;
@@ -315,13 +304,8 @@ void GlScope::initializeGL() {
               gl_PointSize = 1.0;
           }
     )";
-    const char *fshaderDesktop120 = R"(
-          #version 120
-          uniform highp vec4 colour;
-          void main() { gl_FragColor = colour; }
-    )";
 
-    const char *vshaderDesktop150 = R"(
+    const char *vertexShaderGLSL150 = R"(
           #version 150
           in highp vec3 vertex;
           uniform mat4 matrix;
@@ -331,37 +315,68 @@ void GlScope::initializeGL() {
               gl_PointSize = 1.0;
           }
     )";
-    const char *fshaderDesktop150 = R"(
+
+    const char *fragmentShaderGLES = R"(
+          #version 100
+          uniform highp vec4 color;
+          void main() { gl_FragColor = color; }
+    )";
+
+    const char *fragmentShaderGLSL120 = R"(
+          #version 120
+          uniform highp vec4 color;
+          void main() { gl_FragColor = color; }
+    )";
+
+    const char *fragmentShaderGLSL150 = R"(
           #version 150
-          uniform highp vec4 colour;
+          uniform highp vec4 color;
           out vec4 flatColor;
-          void main() { flatColor = colour; }
+          void main() { flatColor = color; }
     )";
 
     if ( GlScope::forceGLSLversion )
         GLSLversion = GlScope::forceGLSLversion;
     // qDebug() << "compile shaders" << GlScope::forceGLSLversion << GLSLversion;
 
-    const char *vshaderDesktop = GLSLversion == 120 ? vshaderDesktop120 : vshaderDesktop150;
-    const char *fshaderDesktop = GLSLversion == 120 ? fshaderDesktop120 : fshaderDesktop150;
-
-    // Compile vertex shader
+    // Compile vertex and fragment shader
+    QString hint;
     bool usesOpenGL = QSurfaceFormat::defaultFormat().renderableType() == QSurfaceFormat::OpenGL;
-    if ( !program->addShaderFromSourceCode( QOpenGLShader::Vertex, usesOpenGL ? vshaderDesktop : vshaderES ) ||
-         !program->addShaderFromSourceCode( QOpenGLShader::Fragment, usesOpenGL ? fshaderDesktop : fshaderES ) ) {
-        errorMessage = tr( "Failed to compile OpenGL shader programs.\n" ) + program->log();
-        return;
+    if ( usesOpenGL ) // in case of error offer a possible solution
+        hint = tr( "Try command line option '--useGLES'\n" );
+
+    if ( 150 == GLSLversion ) { // use version 150 if supported by OpenGL version >= 3.2
+        if ( !program->addShaderFromSourceCode( QOpenGLShader::Vertex, vertexShaderGLSL150 ) ||
+             !program->addShaderFromSourceCode( QOpenGLShader::Fragment, fragmentShaderGLSL150 ) ) {
+            qWarning() << "\nOpenGL version" << OpenGLversion;
+            qWarning() << "To get rid of this error message, try the command line option '--useGLSL120' or '--useGLES'";
+            GLSLversion = 120; // in case of error try version 120 as fall back
+        }
+    }
+    if ( 120 == GLSLversion ) { // this version is supported by OpenGL version >= 2.1 (very old)
+        if ( !program->addShaderFromSourceCode( QOpenGLShader::Vertex, vertexShaderGLSL120 ) ||
+             !program->addShaderFromSourceCode( QOpenGLShader::Fragment, fragmentShaderGLSL120 ) ) {
+            errorMessage = tr( "Failed to compile OpenGL shader programs.\n" ) + hint + program->log();
+            return; // in case of error propose the use of OpenGLES (OpenGL for embedded systems) and stop
+        }
+    }
+    if ( !usesOpenGL ) { // use OpenGLES
+        if ( !program->addShaderFromSourceCode( QOpenGLShader::Vertex, vertexShaderGLES ) ||
+             !program->addShaderFromSourceCode( QOpenGLShader::Fragment, fragmentShaderGLES ) ) {
+            errorMessage = tr( "Failed to compile OpenGL shader programs.\n" ) + program->log();
+            return;
+        }
     }
 
     // Link shader pipeline
     if ( !program->link() || !program->bind() ) {
-        errorMessage = tr( "Failed to link/bind OpenGL shader programs.\n" ) + program->log();
+        errorMessage = tr( "Failed to link/bind OpenGL shader programs.\n" ) + hint + program->log();
         return;
     }
 
     vertexLocation = program->attributeLocation( "vertex" );
     matrixLocation = program->uniformLocation( "matrix" );
-    colorLocation = program->uniformLocation( "colour" );
+    colorLocation = program->uniformLocation( "color" );
 
     if ( vertexLocation == -1 || colorLocation == -1 || matrixLocation == -1 ) {
         qWarning() << tr( "Failed to locate shader variable." );
@@ -383,17 +398,15 @@ void GlScope::initializeGL() {
     QColor bg = view->colors->background;
     gl->glClearColor( GLfloat( bg.redF() ), GLfloat( bg.greenF() ), GLfloat( bg.blueF() ), GLfloat( bg.alphaF() ) );
 
+    m_vaoMarker.create();
+    QOpenGLVertexArrayObject::Binder b( &m_vaoMarker );
+    m_marker.create();
+    m_marker.bind();
+    m_marker.setUsagePattern( QOpenGLBuffer::StaticDraw );
+    m_marker.allocate( int( vaMarker.size() * sizeof( Vertices ) ) );
+    program->enableAttributeArray( vertexLocation );
+    program->setAttributeBuffer( vertexLocation, GL_FLOAT, 0, 3, 0 );
 
-    {
-        m_vaoMarker.create();
-        QOpenGLVertexArrayObject::Binder b( &m_vaoMarker );
-        m_marker.create();
-        m_marker.bind();
-        m_marker.setUsagePattern( QOpenGLBuffer::StaticDraw );
-        m_marker.allocate( int( vaMarker.size() * sizeof( Vertices ) ) );
-        program->enableAttributeArray( vertexLocation );
-        program->setAttributeBuffer( vertexLocation, GL_FLOAT, 0, 3, 0 );
-    }
     updateCursor();
 
     m_program = std::move( program );
@@ -564,6 +577,7 @@ void GlScope::draw4Cross( std::vector< QVector3D > &va, int section, float x, fl
     }
 }
 
+
 // prepare the static grid structure that is shown by 'drawGrid()'
 // show a line as long as the trigger level marker is clicked or moved
 // index: channel, value: trigger level, pressed: marker is activated
@@ -692,7 +706,6 @@ void GlScope::generateGrid( int index, double value, bool pressed ) {
 
     ++item;
 
-
     { // prepare (dynamic) trigger level marker line
         if ( !m_vaoGrid[ item ].isCreated() )
             m_vaoGrid[ item ].create();
@@ -735,7 +748,6 @@ void GlScope::drawGrid() {
     gl->glDrawArrays( GL_POINTS, 0, gridDrawCounts[ item ] );
     m_vaoGrid[ item ].release();
 
-
     // Axes and div crosses
     ++item;
     m_vaoGrid[ item ].bind();

openhantek/src/glscope.h

@@ -124,6 +124,7 @@ class GlScope : public QOpenGLWidget {
     unsigned currentGraphInHistory = 0;
 
     // OpenGL shader, matrix, var-locations
+    QString OpenGLversion;
     unsigned int GLSLversion = 150;
     static unsigned forceGLSLversion;
     bool shaderCompileSuccess = false;

openhantek/translations/openhantek_de.ts

@@ -663,31 +663,45 @@
 <context>
     <name>GlScope</name>
     <message>
-        <location filename="../src/glscope.cpp" line="282"/>
+        <location filename="../src/glscope.cpp" line="276"/>
         <source>System does not support OpenGL Shading Language (GLSL)</source>
         <translation>System unterstützt nicht OpenGL Shading Language (GLSL)</translation>
     </message>
     <message>
-        <location filename="../src/glscope.cpp" line="286"/>
+        <location filename="../src/glscope.cpp" line="280"/>
         <source>OpenGL init called twice!</source>
         <translation>OpenGL init wurde doppelt aufgerufen!</translation>
     </message>
     <message>
-        <location filename="../src/glscope.cpp" line="352"/>
+        <source>Try command line option &apos;--useGLSL120&apos; or &apos;--useGLES&apos;
+</source>
+        <translation type="vanished">Probiere Kommandozeilenoption &apos;--useGLSL120&apos; oder &apos;--useGLES&apos;
+</translation>
+    </message>
+    <message>
+        <location filename="../src/glscope.cpp" line="346"/>
+        <source>Try command line option &apos;--useGLES&apos;
+</source>
+        <translation>Probiere Kommandozeilenoption &apos;--useGLES&apos;
+</translation>
+    </message>
+    <message>
+        <location filename="../src/glscope.cpp" line="359"/>
+        <location filename="../src/glscope.cpp" line="366"/>
         <source>Failed to compile OpenGL shader programs.
 </source>
         <translation>Fehler beim Übersetzen der OpenGL Shader-Programme.
 </translation>
     </message>
     <message>
-        <location filename="../src/glscope.cpp" line="358"/>
+        <location filename="../src/glscope.cpp" line="373"/>
         <source>Failed to link/bind OpenGL shader programs.
 </source>
         <translation>Fehler beim Linken der OpenGL Shader-Programme.
 </translation>
     </message>
     <message>
-        <location filename="../src/glscope.cpp" line="367"/>
+        <location filename="../src/glscope.cpp" line="382"/>
         <source>Failed to locate shader variable.</source>
         <translation>Kann Shader-Variable nicht lokalisieren.</translation>
     </message>