New gcode visualization integration - Added check of OpenGL version

src/slic3r/GUI/LibVGCode/src/OpenGLUtils.cpp

@@ -16,8 +16,10 @@
 
 #include <iostream>
 #include <assert.h>
+#include <cctype>
 
 namespace libvgcode {
+
 #ifdef HAS_GLSAFE
 void glAssertRecentCallImpl(const char* file_name, unsigned int line, const char* function_name)
 {
@@ -40,6 +42,21 @@ void glAssertRecentCallImpl(const char* file_name, unsigned int line, const char
 }
 #endif // HAS_GLSAFE
 
+bool check_opengl_version()
+{
+    bool ret = false;
+    const GLubyte* version = glGetString(GL_VERSION);
+    if (version != nullptr) {
+        const std::string version_str(reinterpret_cast<const char*>(version));
+        if (version_str.length() > 4 && isdigit(version_str[0]) && isdigit(version_str[2])) {
+            const int major = version_str[0] - '0';
+            const int minor = version_str[2] - '0';
+            ret = major > 3 || (major == 3 && minor >= 2);
+        }
+    }
+    return ret;
+}
+
 } // namespace libvgcode
 
 //################################################################################################################################

src/slic3r/GUI/LibVGCode/src/OpenGLUtils.hpp

@@ -31,6 +31,8 @@ inline void glAssertRecentCall() { }
 #define glcheck()
 #endif // HAS_GLSAFE
 
+extern bool check_opengl_version();
+
 } // namespace libvgcode
 
 //################################################################################################################################

src/slic3r/GUI/LibVGCode/src/ViewerImpl.cpp

@@ -298,9 +298,14 @@ ViewerImpl::~ViewerImpl()
 
 void ViewerImpl::init()
 {
-    if (m_segments_shader_id != 0)
+    if (m_initialized)
         return;
 
+    const bool is_valid_opengl_version = check_opengl_version();
+    assert(is_valid_opengl_version);
+    if (!is_valid_opengl_version)
+        throw std::runtime_error("LibVGCode requires an active OpenGL context based on OpenGL 3.2 or higher:\n");
+
     // segments shader
     m_segments_shader_id = init_shader("segments", Segments_Vertex_Shader, Segments_Fragment_Shader);
 
@@ -375,6 +380,8 @@ void ViewerImpl::init()
 
     m_tool_marker.init(32, 2.0f, 4.0f, 1.0f, 8.0f);
 #endif // !ENABLE_NEW_GCODE_VIEWER_NO_COG_AND_TOOL_MARKERS
+
+    m_initialized = true;
 }
 
 void ViewerImpl::reset()

src/slic3r/GUI/LibVGCode/src/ViewerImpl.hpp

@@ -171,6 +171,7 @@ private:
     std::array<float, Time_Modes_Count> m_travels_time{ 0.0f, 0.0f };
     std::vector<uint8_t> m_used_extruders_ids;
 
+    bool m_initialized{ false };
     bool m_loading{ false };
 
     //