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2.1.1.16 MapMode Enumeration

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The MapMode Enumeration defines how logical units are mapped to physical units; that is, assuming that the origins in both the logical and physical coordinate systems are at the same point on the drawing surface, what is the physical coordinate (x',y') that corresponds to logical coordinate (x,y).

For example, suppose the mapping mode is MM_TEXT. Given the following definition of that mapping mode, and an origin (0,0) at the top left corner of the drawing surface, logical coordinate (4,5) would map to physical coordinate (4,5) in pixels.

Now suppose the mapping mode is MM_LOENGLISH, with the same origin as the previous example. Given the following definition of that mapping mode, logical coordinate (4,-5) would map to physical coordinate (0.04,0.05) in inches.

 typedef  enum
 {
   MM_TEXT = 0x0001,
   MM_LOMETRIC = 0x0002,
   MM_HIMETRIC = 0x0003,
   MM_LOENGLISH = 0x0004,
   MM_HIENGLISH = 0x0005,
   MM_TWIPS = 0x0006,
   MM_ISOTROPIC = 0x0007,
   MM_ANISOTROPIC = 0x0008
 } MapMode;

MM_TEXT: Each logical unit is mapped to one device pixel. Positive x is to the right; positive y is down.

MM_LOMETRIC: Each logical unit is mapped to 0.1 millimeter. 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_LOENGLISH: Each logical unit is mapped to 0.01 inch. Positive x is to the right; positive y is up.

MM_HIENGLISH: Each logical unit is mapped to 0.001 inch. Positive x is to the right; positive y is up.

MM_TWIPS: Each logical unit is mapped to one twentieth (1/20) of a point. In printing, a point is 1/72 of an inch; therefore, 1/20 of a point is 1/1440 of an inch. This unit is also known as a "twip".

Positive x is to the right; positive y is up.

MM_ISOTROPIC: Logical units are mapped to arbitrary device units with equally scaled axes; that is, one unit along the x-axis is equal to one unit along the y-axis. The META_SETWINDOWEXT (section 2.3.5.30) and META_SETVIEWPORTEXT (section 2.3.5.28) records specify the units and the orientation of the axes.

The processing application SHOULD make adjustments as necessary to ensure the x and y units remain the same size. For example, when the window extent is set, the viewport SHOULD be adjusted to keep the units isotropic.

MM_ANISOTROPIC: Logical units are mapped to arbitrary units with arbitrarily scaled axes.