From 3404f4e86b8230adba9b402f74beba55a18fe8bb Mon Sep 17 00:00:00 2001
From: Roberto Fernandez Bautista <roberto.fer.bau@gmail.com>
Date: Fri, 30 Oct 2020 19:35:24 +0000
Subject: [PATCH] Check GLEW functions exist before calling them Fixes
 https://gitlab.com/kicad/code/kicad/-/issues/6235

---
 common/gal/opengl/cached_container_gpu.cpp |  7 +++++-
 common/gal/opengl/cached_container_ram.cpp |  4 +++-
 common/gal/opengl/gpu_manager.cpp          |  7 ++++--
 common/gal/opengl/opengl_compositor.cpp    |  7 ++++--
 common/gal/opengl/shader.cpp               | 25 ++++++++++++----------
 5 files changed, 33 insertions(+), 17 deletions(-)

diff --git a/common/gal/opengl/cached_container_gpu.cpp b/common/gal/opengl/cached_container_gpu.cpp
index bca5e078ac..b1da9e3b20 100644
--- a/common/gal/opengl/cached_container_gpu.cpp
+++ b/common/gal/opengl/cached_container_gpu.cpp
@@ -65,7 +65,8 @@ CACHED_CONTAINER_GPU::~CACHED_CONTAINER_GPU()
     if( m_isMapped )
         Unmap();
 
-    glDeleteBuffers( 1, &m_glBufferHandle );
+    if( glDeleteBuffers )
+        glDeleteBuffers( 1, &m_glBufferHandle );
 }
 
 
@@ -73,6 +74,10 @@ 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 ) );
 
diff --git a/common/gal/opengl/cached_container_ram.cpp b/common/gal/opengl/cached_container_ram.cpp
index a306373dfa..7d77d79f80 100644
--- a/common/gal/opengl/cached_container_ram.cpp
+++ b/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 );
 }
 
diff --git a/common/gal/opengl/gpu_manager.cpp b/common/gal/opengl/gpu_manager.cpp
index 93ff22f7e4..48bd0f1fea 100644
--- a/common/gal/opengl/gpu_manager.cpp
+++ b/common/gal/opengl/gpu_manager.cpp
@@ -85,8 +85,11 @@ GPU_CACHED_MANAGER::~GPU_CACHED_MANAGER()
 {
     if( m_buffersInitialized )
     {
-        glBindBuffer( GL_ARRAY_BUFFER, 0 );
-        glDeleteBuffers( 1, &m_indicesBuffer );
+        if( glBindBuffer )
+            glBindBuffer( GL_ARRAY_BUFFER, 0 );
+
+        if( glDeleteBuffers )
+            glDeleteBuffers( 1, &m_indicesBuffer );
     }
 }
 
diff --git a/common/gal/opengl/opengl_compositor.cpp b/common/gal/opengl/opengl_compositor.cpp
index 6fae6014f9..2133cd9477 100644
--- a/common/gal/opengl/opengl_compositor.cpp
+++ b/common/gal/opengl/opengl_compositor.cpp
@@ -399,8 +399,11 @@ void OPENGL_COMPOSITOR::clean()
 
     m_buffers.clear();
 
-    glDeleteFramebuffersEXT( 1, &m_mainFbo );
-    glDeleteRenderbuffersEXT( 1, &m_depthBuffer );
+    if( glDeleteFramebuffersEXT )
+        glDeleteFramebuffersEXT( 1, &m_mainFbo );
+
+    if( glDeleteRenderbuffersEXT )
+        glDeleteRenderbuffersEXT( 1, &m_depthBuffer );
 
     m_initialized = false;
 }
diff --git a/common/gal/opengl/shader.cpp b/common/gal/opengl/shader.cpp
index d78379c36b..f61ede2cd0 100644
--- a/common/gal/opengl/shader.cpp
+++ b/common/gal/opengl/shader.cpp
@@ -59,20 +59,23 @@ SHADER::~SHADER()
 
     if( isProgramCreated )
     {
-        // Delete the shaders and the program
-        for( std::deque<GLuint>::iterator it = shaderNumbers.begin();
-                it != shaderNumbers.end(); ++it )
+        if( glIsShader )
         {
-            GLuint shader = *it;
-
-            if( glIsShader( shader ) )
+            // Delete the shaders and the program
+            for( std::deque<GLuint>::iterator it = shaderNumbers.begin(); it != shaderNumbers.end();
+                    ++it )
             {
-                glDetachShader( programNumber, shader );
-                glDeleteShader( shader );
-            }
-        }
+                GLuint shader = *it;
 
-        glDeleteProgram( programNumber );
+                if( glIsShader( shader ) )
+                {
+                    glDetachShader( programNumber, shader );
+                    glDeleteShader( shader );
+                }
+            }
+
+            glDeleteProgram( programNumber );
+        }
     }
 }