Function RTSetDisplayHandler

RTSetDisplayHandler installs one of the predefined display handlers to handle characters to be displayed by TTY type functions (e.g., WriteFile for stdout/stderr, printf, writeln, RTDisplayString, etc.). Console I/O functions such as WriteConsoleOutput are not affected by the display char handler.

Parameters

Type

Value	Meaning
RT_DISP_DETECT	If a video RAM is present, the RT_DISP_SCREEN handler is installed. Otherwise, if the display is operated in a 32 bit graphics mode, RT_DISP_GRAPHICS is used. Otherwise, if the program is running under the Debug Monitor's control, the RT_DISP_HOST handler is installed. As a last resort, the RT_DISP_NONE handler is used.
RT_DISP_NONE	Any data to be displayed is discarded.
RT_DISP_SCREEN	Characters are displayed by writing them to the video RAM operated in VGA Text mode. The output position for the next character is advanced automatically. Characters CR, LF, TAB, and BS only move the output position and do not display any text. Character FF clears the screen and returns the output position to the upper left-hand corner. The physical cursor is not used.
RT_DISP_HOST	The data is passed on to the Debug Monitor which will in turn send it to the host. If the debugger or RTRun is running in non-detached mode, the data is displayed on the host.
RT_DISP_GRAPHICS	This handler works much like the RT_DISP_SCREEN handler. Characters are displayed using an 8x16 font, code page OEM 437.

return value

The function will not install the requested display handler if the resources required by that handler are not available. Instead, RT_DISP_DETECT is assumed (for example, RT_DISP_HOST is requested and the program does not run under the Debug Monitor, or RT_DISP_SCREEN is used, but VideoRAM = None was specified in the configuration file).

If none of the predefined char out handlers are suitable, an application can install a custom handler in global variable:

For example, such a handler could be used to redirect all screen output to a serial port.