The display

The display represents the whole area on the monitor. It has a size (typically 1024x768, or 1280x1024), a color depth, that is, the number of bits that are used to represent a single pixel (typically 16 = High Color or 32 = Full Color) and a refresh frequency, that is, the number of times per second the display is refreshed (typically between 60 and 120). These settings can normally be changed though the display properties. For games though, in particular when they run in full-screen mode, it is important to be able to change these settings. All these settings can be initialized for the game in the Game Settings. For use during game play the following functions exist. Note though that changing the settings during game play will result in a time delay as things has to be rebuilt. The functions to set the mode are only available in the Standard Edition.

display_get_width() Returns the width of the display in pixels.
display_get_height() Returns the height of the display in pixels.
display_get_colordepth() Returns the color depth in bits.
display_get_frequency() Returns the refresh frequency of the display.
display_set_size(w,h) Sets the width and height of the display in pixels. Returns whether this was successful. (Realize that only certain combinations are allowed.)
display_set_colordepth(coldepth) Sets the color depth. In general only 16 and 32 are allowed values. Returns whether successful.
display_set_frequency(frequency) Sets the refresh frequency for the display. Only few frequencies are allowed. Typically you could set this to 60 with a same room speed to get smooth 60 frames per second motion. Returns whether successful.
display_set_all(w,h,frequency,coldepth) Sets all at once. Use -1 for values you do not want to change. Returns whether successful.
display_test_all(w,h,frequency,coldepth) Tests whether the indicated settings are allowed. It does not change the settings. Use -1 for values you do not want to change. Returns whether the settings are allowed.
display_reset(AA) Resets the display settings to the ones when the program was started, and also allow you to change the current level of Full Screen Anti-Aliasing being used. Available levels are 0,2,4 and 8. GameMaker start up with 0.
display_aa This read-only variable will report the various levels of AA that a users machine can display. It will do this by setting bits for the different levels, so for only 2xAA, this will report 2, for 2x and 4x availablility it will report 6. For 8 and 4 it will report 12. For all 3 levels (2,4 and 8) it will report 14. To allow a user to set AA, use something like the code shown below.. 
  if( display_aa&2 ) display_reset(2);

Sometimes it is useful to get information about the position of the mouse on the display or to change this position. For this the following functions exist:

display_mouse_get_x() Returns the x-coordinate of the mouse on the display.
display_mouse_get_y() Returns the y-coordinate of the mouse on the display.
display_mouse_set(x,y) Sets the position of the mouse on the display to the indicated values.