hlsdk

#include <tier3/tier3.h>

#define _____assert_ptr( something, name ) if (!something) Msg("[MS] Failed to assert %s\n", name)
void GetGlobalInterfacePointers( CreateInterfaceFn VGUIFactory, CreateInterfaceFn VGUI2Factory )
{
    g_pVGuiSurface = (vgui::ISurface*)VGUIFactory(VGUI_SURFACE_INTERFACE_VERSION, NULL);
        _____assert_ptr(g_pVGuiSurface, "g_pVGuiSurface");

    g_pVGuiInput = (vgui::IInput*)VGUI2Factory(VGUI_INPUT_INTERFACE_VERSION, NULL);
        _____assert_ptr(g_pVGuiInput, "g_pVGuiInput");

    g_pVGui = (vgui::IVGui*)VGUI2Factory(VGUI_IVGUI_INTERFACE_VERSION, NULL);
        _____assert_ptr(g_pVGui, "g_pVGui");

    g_pVGuiPanel = (vgui::IPanel*)VGUI2Factory(VGUI_PANEL_INTERFACE_VERSION, NULL);
        _____assert_ptr(g_pVGuiPanel, "g_pVGuiPanel");

    g_pVGuiSchemeManager = (vgui::ISchemeManager*)VGUI2Factory(VGUI_SCHEME_INTERFACE_VERSION, NULL);
        _____assert_ptr(g_pVGuiSchemeManager, "g_pVGuiSchemeManager");

    g_pVGuiSystem = (vgui::ISystem*)VGUI2Factory(VGUI_SYSTEM_INTERFACE_VERSION, NULL);
        _____assert_ptr(g_pVGuiSystem, "g_pVGuiSystem");

    g_pEngineVGui = (IEngineVGui*) g_AppSystemFactory( "VEngineVGui001", NULL );
        _____assert_ptr(g_pEngineVGui, "g_pEngineVGui");
}

//  \/ This goes in plugin load or CON_COMMAND hook or whatever. Declare a global instance: CVMTHook g_PAINTTRAVERSEHOOK;
g_PaintTraverseHook.Hook( (DWORD) &Hooked_PaintTraverse, (PDWORD) g_pVGuiPanel, 40 );

Then:

void __stdcall Hooked_PaintTraverse(VPANEL vguiPanel, bool forceRepaint, bool allowForce = true)
{
    g_PaintTraverseHook.UnHook();
    g_pVGuiPanel->PaintTraverse(vguiPanel, forceRepaint, allowForce);
    g_PaintTraverseHook.ReHook();

    //This gets called multiple times / frame
    //You probably want to if(FStrEq(g_pEngineVGui->GetPanel(vguiPanel)->GetName(), "MatSysTopPanel"))
    //if you want to draw like a s3x0r.
}