Environment > Setting Preferences > General Graphics Preferences

# General Graphics Preferences

Preferences in this category are supported by all versions of IDL.

## IDL_GR_TILECACHESIZE

The IDL_GR_TILECACHESIZE preference controls how much memory (in megabytes) IDL can use for caching image tiles. IDL allocates memory for caching a tile each time IDLgrImage::SetTileData is called. When the amount of allocated memory reaches the value of IDL_GR_TILECACHESIZE, the least recently viewed tile or tiles are freed to make room for the new tile. Therefore, the amount of memory used for caching tiles will not grow above this value.

Committed changes take effect immediately. The default value is 0.

If set to 0, there is no limit imposed on the amount of memory used for tiling; memory usage will continue to grow as more tiles are cached. This can result in the operating system paging memory to and from disk when physical RAM is exhausted.

This preference can be set in the IDL Workbench Preferences dialog.

## IDL_GR_TTCACHESIZE

IDL saves TrueType fonts as a set of glyphs; each glyph represents the triangulation data for drawing one character. To minimize the number of times common glyphs must be computed, IDL uses a cache to retain recently computed glyphs in the hope that they can be reused. When IDL finds a needed glyph in the cache, it uses the glyph immediately without rebuilding it. The IDL_GR_TTCACHESIZE preference sets the size of the TrueType glyph cache. It must be set to a value greater than or equal to 1.

Committed changes take effect immediately. The default value is 256, roughly two TrueType font sets.

This preference can be set in the IDL Workbench Preferences dialog.