The shape of a geometric line is determined by the width, join style, and end-cap style of the brush and the current world-to-device transform in the XFORMOBJ. The line can be drawn using either a solid or a nonsolid brush.
Drivers for more advanced hardware may support geometric wide lines in DrvStrokePath. GDI determines whether a driver can draw a path containing a geometric line by testing the GCAPS_GEOMETRICWIDE capability flag in the DEVINFO structure returned in DrvEnablePDEV. If the driver does not have the capability, or if the function refuses to handle an operation because the path or clipping is too complex for the device, GDI automatically transforms the call to the simpler DrvFillPath or DrvPaint functions.
A geometric wide line has a specific meaning to a display driver graphics function. A path containing device coordinates is transformed to world coordinates using the inverse of the current transform. A geometric construction with the specified width then obtains a widened version of the path, taking into account joins and end caps. This path is transformed to device coordinates again and filled with the specified brush.
Styling of a geometric wide line is specified by an array of floating-point values. The array has a finite length, but is used as though it repeats indefinitely. The first array entry specifies the length, in world coordinates, of the first dash; and the next entry specifies the length of the first gap. After this, lengths of dashes and gaps alternate. For example, the style array {3.0,1.0,1.0,1.0} causes a line to be drawn with alternating long and short dashes.
Styling can be thought of as the driver moving along a path before widening, “erasing” the parts of the path corresponding to the gaps. This breaks the path into many subpaths. The broken path is then widened as if it has no line style, applying end caps and joins as usual. Style arrays can be of odd length. For example, the style array {1.0} causes a line to drawn with alternating dashes. The style state (defined as the current distance into the styling array) is provided for the beginning of the first subpath in a path. It is assumed to be reset to 0.0 at the beginning of each subsequent subpath, which occurs after any Win32 MoveToEx operation.