I am working on a legacy ActiveX control that implements custom drawing of elementary Windows controls like combo button and check box. If the Windows visual styles are available, these controls are drawn with the DrawThemeBackground function like this:
res = DrawThemeBackground(hTheme, hDC, lPartId, lStateId, rcDraw, rcDraw);
The ActiveX's initialization code contains calls to InitCommonControls/InitCommonControlsEx. Do we need these calls if OS-styled combo buttons and check boxes are not created with CreateWindowEx and are fully custom drawn?