fix(webgl): Add VAO support for WebGL 2.0 rendering

WebGL 2.0 / OpenGL ES 3.0 requires a Vertex Array Object (VAO) to be
bound before setting vertex attributes. Desktop OpenGL has a default
VAO (VAO 0), but WebGL 2.0 does not.

Changes to GPU_MANAGER:
- Add m_vao member variable to store VAO handle
- Create VAO in SetShader() when GL context is available
- Bind VAO before glVertexAttribPointer calls in EndDrawing()
- Unbind VAO after rendering completes
- Delete VAO in destructor

This fix enables actual rendering output in WebGL. Without a VAO,
glVertexAttribPointer silently fails and no geometry is drawn.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

tests/gal-regression/wasm/webgl/gpu_manager.cpp

@@ -61,13 +61,20 @@ GPU_MANAGER::GPU_MANAGER( VERTEX_CONTAINER* aContainer ) :
         m_shaderAttrib( 0 ),
         m_vertexAttrib( 0 ),
         m_colorAttrib( 0 ),
-        m_enableDepthTest( true )
+        m_enableDepthTest( true ),
+        m_vao( 0 )
 {
 }
 
 
 GPU_MANAGER::~GPU_MANAGER()
 {
+    // Delete VAO if it was created
+    if( m_vao != 0 )
+    {
+        glDeleteVertexArrays( 1, &m_vao );
+        m_vao = 0;
+    }
 }
 
 
@@ -82,6 +89,13 @@ void GPU_MANAGER::SetShader( SHADER& aShader )
     {
         DisplayError( nullptr, wxT( "Could not get the shader attribute location" ) );
     }
+
+    // Create VAO for WebGL 2.0 / OpenGL ES 3.0 compatibility
+    // WebGL 2.0 requires a VAO to be bound before calling glVertexAttribPointer
+    if( m_vao == 0 )
+    {
+        glGenVertexArrays( 1, &m_vao );
+    }
 }
 
 
@@ -163,6 +177,9 @@ void GPU_CACHED_MANAGER::EndDrawing()
     else
         glDisable( GL_DEPTH_TEST );
 
+    // Bind VAO first (required for WebGL 2.0 / OpenGL ES 3.0)
+    glBindVertexArray( m_vao );
+
     // Bind vertices data buffers
     glBindBuffer( GL_ARRAY_BUFFER, cached->GetBufferHandle() );
 
@@ -250,6 +267,9 @@ void GPU_CACHED_MANAGER::EndDrawing()
         m_shader->Deactivate();
     }
 
+    // Unbind VAO
+    glBindVertexArray( 0 );
+
     m_isDrawing = false;
 }
 
@@ -301,6 +321,9 @@ void GPU_NONCACHED_MANAGER::EndDrawing()
     else
         glDisable( GL_DEPTH_TEST );
 
+    // Bind VAO first (required for WebGL 2.0 / OpenGL ES 3.0)
+    glBindVertexArray( m_vao );
+
     // Modern vertex attributes (replacing legacy glEnableClientState/glVertexPointer/glColorPointer)
     // Vertex position (a_vertex)
     glEnableVertexAttribArray( m_vertexAttrib );
@@ -338,6 +361,9 @@ void GPU_NONCACHED_MANAGER::EndDrawing()
         m_shader->Deactivate();
     }
 
+    // Unbind VAO
+    glBindVertexArray( 0 );
+
     m_container->Clear();
 
 #ifdef KICAD_GAL_PROFILE

tests/gal-regression/wasm/webgl/gpu_manager.h

@@ -98,6 +98,10 @@ protected:
 
     ///< true: enable Z test when drawing
     bool m_enableDepthTest;
+
+    ///< VAO for WebGL 2.0 / OpenGL ES 3.0 compatibility
+    ///< WebGL 2.0 requires a VAO to be bound before setting vertex attributes
+    unsigned int m_vao;
 };