README.TXT

Dynamically Changing the Display Settings 
 
 
The SetDisp sample creates a taskbar notification icon that you can use to 
dynamically change your display settings. You can change resolution, color 
depth, and refresh rate. 
 
The core functions used are: 
                                                               
   EnumDisplaySettings -- to get the display settings that are supported by 
  the video driver 
 
   ChangeDisplaySettings -- to test and set the display  settings dynamically 
  and to update the registry with these settings 
 
   Shell_NotifyIcon -- to create and maintain the tray icon    
 
   TrackPopupMenu   -- to implement the icon resolution context menu 
 
 
Usage 
------ 
 
To use the sample after building it with NMAKE, run SetDisp.EXE.  This will 
display a dialog box with a menu of possible resolutions and a will create a 
tray icon. If you right mouse click on the tray icon the dialog will get 
the focus.  If you hide the dialog, you can bring it back up with this 
technique.  If you left mouse click the tray icon, you will get the list of 
available settings. To remove the tray icon, you must close the main dialog. 
 
When SetDisp starts up, it enumerates all of the device modes that the current 
or default display driver supports.  A #define controls filtering low frequency 
refresh rates and limits the number of settings SetDisp reads in.  After 
enumerating the settings, they are added to the menu. On NT, we can easily 
obtain the current setting with ENUM_CURRENT_SETTINGS, so we set the check 
mark on the menu and bold the setting that was in use when SetDisp was 
started. 
 
When you select a new setting, SetDisp test to be sure the DEVMODE selected 
has one of the display attributes set.All of the DEVMODEs used in SetDisp 
should have these set since they came from the system.It then tests to see if 
the system believes the DEVMODE is valid. If the change requires a system 
reboot, a dialog notifies the user that this is not implemented. If the screen 
change can be dynamic, a resolution changed is attempted.  The user is prompted 
to see if the new resolution is acceptable.  This is important since the driver 
may support a setting but the monitor is not able to display it correctly.  To 
ensure the user does not get stuck with a bad setting, a timer is used to 
cancel the change if the user does not respond. The default time out is 10 
seconds and is controlled by a #define.If the new setting is accepted, the 
registry is updated.  All of this is done using ChangeDisplaySettings. 
 
 
Notes 
----- 
 
On Windows 95, you cannot use EnumDisplaySettings to get the current settings. 
In this sample, this causes the check mark to not be displayed and the 
current setting to not be made bold. Also on Windows 95, color depth changes  
require a reboot. 
 
Of the possible returns from ChangeDisplaySettings, only success and a reboot 
required are currently handled.For success, a dynamic resolution change is 
done.  For a reboot required change, a message is displayed indicating that 
the sample does not support a reboot. 
 
If your driver has many resolutions, the menu may not fit on some resolutions. 
This could be resolved with the use of sub menus for different settings 
such as color depth or frequencies.