Check GLEW functions exist before calling them

Fixes https://gitlab.com/kicad/code/kicad/-/issues/6235

common/gal/opengl/cached_container_gpu.cpp

@@ -67,7 +67,8 @@ CACHED_CONTAINER_GPU::~CACHED_CONTAINER_GPU()
     if( m_isMapped )
         Unmap();
 
-    glDeleteBuffers( 1, &m_glBufferHandle );
+    if( glDeleteBuffers )
+        glDeleteBuffers( 1, &m_glBufferHandle );
 }
 
 
@@ -75,6 +76,10 @@ void CACHED_CONTAINER_GPU::Map()
 {
     wxCHECK( !IsMapped(), /*void*/ );
 
+    // OpenGL version might suddenly stop being available in Windows when an RDP session is started
+    if( !glBindBuffer )
+        throw std::runtime_error( "OpenGL no longer available!" );
+
     glBindBuffer( GL_ARRAY_BUFFER, m_glBufferHandle );
     m_vertices = static_cast<VERTEX*>( glMapBuffer( GL_ARRAY_BUFFER, GL_READ_WRITE ) );
 

common/gal/opengl/cached_container_ram.cpp

@@ -51,7 +51,9 @@ CACHED_CONTAINER_RAM::CACHED_CONTAINER_RAM( unsigned int aSize ) :
 
 CACHED_CONTAINER_RAM::~CACHED_CONTAINER_RAM()
 {
-    glDeleteBuffers( 1, &m_verticesBuffer );
+    if( glDeleteBuffers )
+        glDeleteBuffers( 1, &m_verticesBuffer );
+
     free( m_vertices );
 }
 

common/gal/opengl/gpu_manager.cpp

@@ -85,8 +85,11 @@ GPU_CACHED_MANAGER::~GPU_CACHED_MANAGER()
 {
     if( m_buffersInitialized )
     {
-        glBindBuffer( GL_ARRAY_BUFFER, 0 );
+        if( glBindBuffer )
-        glDeleteBuffers( 1, &m_indicesBuffer );
+            glBindBuffer( GL_ARRAY_BUFFER, 0 );
+
+        if( glDeleteBuffers )
+            glDeleteBuffers( 1, &m_indicesBuffer );
     }
 }
 

common/gal/opengl/opengl_compositor.cpp

@@ -400,8 +400,11 @@ void OPENGL_COMPOSITOR::clean()
 
     m_buffers.clear();
 
-    glDeleteFramebuffersEXT( 1, &m_mainFbo );
+    if( glDeleteFramebuffersEXT )
-    glDeleteRenderbuffersEXT( 1, &m_depthBuffer );
+        glDeleteFramebuffersEXT( 1, &m_mainFbo );
+
+    if( glDeleteRenderbuffersEXT )
+        glDeleteRenderbuffersEXT( 1, &m_depthBuffer );
 
     m_initialized = false;
 }

common/gal/opengl/shader.cpp

@@ -59,20 +59,23 @@ SHADER::~SHADER()
 
     if( isProgramCreated )
     {
-        // Delete the shaders and the program
+        if( glIsShader )
-        for( std::deque<GLuint>::iterator it = shaderNumbers.begin();
-                it != shaderNumbers.end(); ++it )
         {
-            GLuint shader = *it;
+            // Delete the shaders and the program
-
+            for( std::deque<GLuint>::iterator it = shaderNumbers.begin(); it != shaderNumbers.end();
-            if( glIsShader( shader ) )
+                    ++it )
             {
-                glDetachShader( programNumber, shader );
+                GLuint shader = *it;
-                glDeleteShader( shader );
-            }
-        }
 
-        glDeleteProgram( programNumber );
+                if( glIsShader( shader ) )
+                {
+                    glDetachShader( programNumber, shader );
+                    glDeleteShader( shader );
+                }
+            }
+
+            glDeleteProgram( programNumber );
+        }
     }
 }