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(
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HDC hdc, |
// handle of device context |
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int fnMapMode |
// new mapping mode |
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); |
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Value |
Description |
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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 that you want. |
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MM_HIENGLISH |
Each logical unit is mapped to 0.001 inch. Positive x is to the right; positive y is up. |
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MM_HIMETRIC |
Each logical unit is mapped to 0.01 millimeter. Positive x is to the right; positive y is up. |
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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 that you want. Graphics device interface (GDI) makes adjustments as necessary to ensure the x and y units remain the same size (for example, if you set the window extent, the viewport will be adjusted to keep the units isotropic). |
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MM_LOENGLISH |
Each logical unit is mapped to 0.01 inch. Positive x is to the right; positive y is up. |
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MM_LOMETRIC |
Each logical unit is mapped to 0.1 millimeter. Positive x is to the right; positive y is up. |
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MM_TEXT |
Each logical unit is mapped to one device pixel. Positive x is to the right; positive y is down. |
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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. |
If the function succeeds, the return value identifies the previous mapping mode.
If the function fails, the return value is zero. To get extended error information, call GetLastError.
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.
GetMapMode, SetViewportExtEx, SetViewportOrgEx, SetWindowExtEx, SetWindowOrgEx