SetMapMode

SetMapMode

The SetMapMode function sets the mapping mode of the specified device context. The mapping mode defines the unit of measure used to transform page-space units into device-space units, and also defines the orientation of the device's x and y axes.

int SetMapMode(
  HDC hdc,        // handle of device context
  int fnMapMode   // new mapping mode
);
 

Parameters

hdc

Handle to the device context.

fnMapMode

Specifies the new mapping mode. It can be any one of the following values:

Value	Description
MM_ANISOTROPIC	Logical units are mapped to arbitrary units with arbitrarily scaled axes. Use the SetWindowExtEx and SetViewportExtEx functions to specify the units, orientation, and scaling.
MM_HIENGLISH	Each logical unit is mapped to 0.001 inch. Positive x is to the right; positive y is up.
MM_HIMETRIC	Each logical unit is mapped to 0.01 millimeter. Positive x is to the right; positive y is up.
MM_ISOTROPIC	Logical units are mapped to arbitrary units with equally scaled axes; that is, one unit along the x-axis is equal to one unit along the y-axis. Use the SetWindowExtEx and SetViewportExtEx functions to specify the units and the orientation of the axes. Graphics device interface (GDI) makes adjustments as necessary to ensure the x and y units remain the same size (When the window extent is set, the viewport will be adjusted to keep the units isotropic).
MM_LOENGLISH	Each logical unit is mapped to 0.01 inch. Positive x is to the right; positive y is up.
MM_LOMETRIC	Each logical unit is mapped to 0.1 millimeter. Positive x is to the right; positive y is up.
MM_TEXT	Each logical unit is mapped to one device pixel. Positive x is to the right; positive y is down.
MM_TWIPS	Each logical unit is mapped to one twentieth of a printer's point (1/1440 inch, also called a "twip"). Positive x is to the right; positive y is up.

Return Values

If the function succeeds, the return value identifies the previous mapping mode.

If the function fails, the return value is zero.

Windows NT: To get extended error information, call GetLastError.

Remarks

The MM_TEXT mode allows applications to work in device pixels, whose size varies from device to device.

The MM_HIENGLISH, MM_HIMETRIC, MM_LOENGLISH, MM_LOMETRIC, and MM_TWIPS modes are useful for applications drawing in physically meaningful units (such as inches or millimeters).

The MM_ISOTROPIC mode ensures a 1:1 aspect ratio.

The MM_ANISOTROPIC mode allows the x-coordinates and y-coordinates to be adjusted independently.

QuickInfo

Windows NT: Requires version 3.1 or later.
Windows: Requires Windows 95 or later.
Windows CE: Unsupported.
Header: Declared in wingdi.h.
Import Library: Use gdi32.lib.

See Also

Coordinate Spaces and Transformations Overview, Coordinate Space and Transformation Functions, GetMapMode, SetViewportExtEx, SetViewportOrgEx, SetWindowExtEx, SetWindowOrgEx