The following little commandline tool, written in Delphi, demonstrates how to retrieve all available screen resolutions (width, height, number of colors and display frequency), and how to modify the current setting.
If you run the executable in a DOS box, it will write all possible settings to standard output.
If you provide a set of settings e.g. 800 600 256 85, then it will switch to this (provided, that your drivers allow the setting).
{$APPTYPE CONSOLE}
// commandline use: DisplayMode 800 600 256 85
// no arguments: it will list all modi.
program DisplayMode;
uses
SysUtils, Messages, Windows;
{$R *.RES}
var
i: Integer;
DevMode: TDevMode;
begin
i := 0;
if ParamCount=0 then
begin
while EnumDisplaySettings(nil, i, DevMode) do
begin
with DevMode do
Writeln(Format('%dx%d %d Colors, %d Hz', [dmPelsWidth, dmPelsHeight,
Int64(1) shl dmBitsperPel, dmDisplayFrequency]));
inc(i);
end;
Writeln('-----');
Writeln('Usage: DisplayMode ');
Writeln('Example: DisplayMode 800 600 65536 85');
end
else
begin
while EnumDisplaySettings(nil, i, DevMode) do
begin
with DevMode do
begin
if (paramstr(1)=IntToStr(dmPelsWidth)) and
(paramstr(2)=IntToStr(dmPelsHeight)) and
(paramstr(3)=IntToStr(Int64(1) shl dmBitsperPel)) and
(paramstr(4)=IntToStr(dmDisplayFrequency)) then
begin
ChangeDisplaySettings(DevMode, CDS_UPDATEREGISTRY);
SendMessage(HWND_BROADCAST, WM_DISPLAYCHANGE, SPI_SETNONCLIENTMETRICS, 0);
break;
end;
end;
inc(i);
end
end;
end.