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# Mapping Mode

gl2 command values are in logical units and the mapping mode affects how logical units are mapped onto the display surface. The mapping modes are:
MM_DEFAULT lower left 0 0, upper right 1000 1000
MM_RIGHTDOWN upper left 0 0, lower right 1000 1000
MM_RAW upper left 0 0, values are pixels
MM_TWIPS upper left 0 0, values are twips (win32 only)
glmap sets the mapping mode.
MM_DEFAULT
The default is a logical drawing surface that has 0 0 as its lower left corner and 1000 1000 as its upper right corner. The x axis starts at 0 and is positive to the right. The y axis starts at 0 and is positive upwards.
The windowport is the drawing represented by the drawing commands. The viewport is the surface (screen window or printer paper) that the drawing is drawn on.
The scaling is based on the ratio between the x and y extents of the viewport and windowport. It is the ratios of these extents that is important, not the individual values.
The viewport (drawing surface) origin is fixed as 0 0 in the lower left corner. The viewport extent is fixed as the pixels in the x and y directions. These values can not be changed by commands. However, as the window on the screen is resized, the viewport extents change.
The default windowport (drawing) is 0 0 and the default windowport extent is 1000 1000. The glwindoworg command changes the origin and the glwindowext command changes the extent.
MM_RIGHTDOWN
This is the same as MM_DEFAULT except the y axis is flipped. The upper left corner is 0 0 and the lower right corner is 1000 1000. The x axis starts at 0 and is positive to the right. The y axis starts at 0 and is positive downwards.
MM_RAW
Values are in pixels and the drawing is directly to the pixels on the drawing surface. The upper left corner is 0 0 and x goes to the right and y goes down. The resize event (glwantresize) can be used to redraw based on the new pixel size of the control.
MM_TWIPS
This mode is supported only in JFEwdw (win32 only). It is similar to MM_RAW except that the logical units are in twips and are scaled to the device. A twip is a "twentieth of a point". A point is approximately 1/72 of an inch and in computer systems a twip is considered to be exactly 1/1440 of an inch. This mode is particularly suited to laying out text and graphs for printing.

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