Browse Prior Art Database

X-Windows Line Style in Hardware with Increased Performance

IP.com Disclosure Number: IPCOM000115004D
Original Publication Date: 1995-Feb-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 4 page(s) / 101K

Publishing Venue

IBM

Related People

Lawless, WF: AUTHOR

Abstract

We have all seen lines drawn on a computer monitor that were dashed or doted or some sort of pattern to them; this is known as Line Style. Typically the Pattern for the Line Style is loaded in memory somewhere and the software super-imposes this over the line when drawn into a graphics Frame Buffer. When the end of the pattern is reached it will go back to the beginning and repeat itself. This is a very slow process and the rendering performance is very slow for this type of operation.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

X-Windows Line Style in Hardware with Increased Performance

      We have all seen lines drawn on a computer monitor that were
dashed or doted or some sort of pattern to them; this is known as
Line Style.  Typically the Pattern for the Line Style is loaded in
memory somewhere and the software super-imposes this over the line
when drawn into a graphics Frame Buffer.  When the end of the pattern
is reached it will go back to the beginning and repeat itself.  This
is a very slow process and the rendering performance is very slow for
this type of operation.

      This invention disclosure will show how a pattern is loaded
into hardware registers and the hardware Line drawing algorithm and
Line Style Hardware work together to increase performance.

      Line Style Registers used in Hardware - The following are three
registers that are needed in Hardware to draw lines with a pattern.
The format in this design matches that of X-Windows but will be
similar for other types of Graphical User Interfaces.

The Line Style Register is shown in Fig. 1.

      Description - These registers are loaded with the pattern to be
used during line rendering.  Each dash can be between 0 and 255
pixels in length.  A value of zero will cause that field to be
skipped and will extend a dash pasted 255 pixels if needed.  A solid
line will be drawn if all fields are set to 00.

      The On pixels are drawn in the foreground color, and the Off
pixels are drawn in the background color when in opaque mode and are
not even updated when in transparent mode.
  Bit <24-31>: Number of Pixels Off.
  Bit <16-23>: Number of Pixels On.
  Bit <08-15>: Number of Pixels Off.
  Bit <00-07>: Number of Pixels On.

      This  registers  are  loaded  with Line Style to be Drawn, each
dash can have a number of pixels from 00 - FF, a value of 0 means  to
skip that dash.
  Bit <24-31>: Number of Pixels Off.
  Bit <16-23>: Number of Pixels On.
  Bit <08-15>: Number of Pixels Off.
  Bit <00-07>: Number of Pixels On.

ON pixel = Foreground colo...