BCGControlBar Pro for MFC
void CBCGPRibbonComboBox::EnableDropDownListResize ( BOOL  bEnable = FALSE)

Enables or disables resizing of drop down list.

Drop down list of combo box button is implemented as a gallery, therefore it's possible to resize it. Use this method to enable or disable resizing of the drop down list.

bEnableSpecifies whether resizing should be enabled or disabled. TRUE - enable resizing, FALSE - disable resizing.