GameUI

Not to be confused with the game_ui entity.

GameUI is the code which provides the VGUI 'frontend': broadly speaking, the main menu and loading screens.

GameUI panels are children of their own dedicated panel ("GameUI Panel"). The client's RootPanel is used only for in-game HUD elements.

Source 2009

Source 2009 GameUI. Closed source.

In Source 2009 (and earlier), GameUI is a closed engine library manipulable to a limited extent by editing .res script files. These define properties like width, height, element location, and so on. You can add new non-interactive elements, and with a bit of effort hide existing ones.

It is possible to create new VGUI panels that behave in exactly the same way as GameUI ones.

Left 4 Dead

Left 4 Dead branch GameUI. Alien Swarm's SDK provides the code.

The Alien Swarm SDK contains the complete source for the newer L4D-style GameUI, which has been moved into the client library. It has been redesigned for consoles' lack of a pointing device: everything is integrated into the same navigable menu system, and you can't be in more than area at once. It's also far, far easier to program.

Tip:VGUI panels very similar to Source 2009 ones can still be created with this incarnation of the code.

Creating a new window

1. Create a new class, inheriting from CBaseModFrame.
2. Create an accompanying "<class name>.res" script in game\resource\ui\basemodui\.
3. Add a new entry to the WINDOW_TYPE enum.
4. Edit the enormous switch in CBaseModPanel::OpenWindow() to include your new enum and class.

The ugly enum/switch indirection is presumably designed to allow a single "window type" value to open slightly different window objects depending on the UI's state. Too bad Valve haven't found any excuse to do that yet!

Opening windows

Use CBaseModFrame* CBaseModPanel::OpenWindow():

#include "gameui\swarm\basemodpanel.h"

using namespace BaseModUI;

void openwindow()
{
	CBaseModFrame* mainMenu = CBaseModPanel::GetSingleton().GetWindow( WT_MAINMENU );
	CBaseModPanel::GetSingleton().OpenWindow( WT_GAMESETTINGS, mainMenu );
}

The arguments are:

WINDOW_TYPE &wt

An enum value that defines which precise window to open.

CBaseModFrame* caller

The window which requested this one to open. Among other things, this becomes the target of 'back' buttons on the new window.

bool hidePrevious

Hides caller if true.

KeyValues* pParameters

Passed on to the new window.

OnOpen() is called on the opened window.

Startup

The initialization sequence is:

1. CGameUI::Initialize()
2. CBaseModPanel::RunFrame()
3. CBaseModPanel::OnGameUIActivated()
4. CBaseModPanel::OpenFrontScreen()
5. CBaseModPanel::OpenWindow()

CBaseModPanel is a singleton; CBaseModFrame is the base class of all windows.