int SetMapMode(hDC,nMapMode)
This function sets the mapping mode of the specified device context. The mapping mode defines the unit of measure used to transform logical units into device units, and also defines the orientation of the device's x- and y-axes. GDI uses the mapping mode to convert logical coordinates into the appropriate device coordinates.
| Parameter | Type/Description |
| hDC | HDC Identifies the device context. | |
| nMapMode | int Specifies the new mapping mode. It can be any one of the values shown in Table R.15, “Mapping Modes.” |
The return value specifies the previous mapping mode.
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 that need to draw in physically meaningful units (such as inches or millimeters).
The MM_ISOTROPIC mode ensures a 1:1 aspect ratio, which is useful when preserving the exact shape of an image is important.
The MM_ANISOTROPIC mode allows the x- and y-coordinates to be adjusted independently.
Table R.15 shows the value and meaning of the various mapping modes:
Table R.15 Mapping Modes
| Value | Meaning |
| MM_ANISOTROPIC | Logical units are mapped to arbitrary units with arbitrarily scaled axes. The SetWindowExt and SetViewportExt functions must be used to specify the desired 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. The SetWindowExt and SetViewportExt functions must be used to specify the desired units and the orientation of the axes. GDI makes adjustments as necessary to ensure that the x and y units remain the same size. |
| 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). Positive x is to the right; positive y is up. |