Dash Patterns
- Preface
- Introduction
- Tutorial
- Implementation
- Commands
- bitmap
- eval-wish
- get-tk-var
- photo
- set-tk-var!
- tk
- tk-id->widget
- tk-var
- tk/after
- tk/appname
- tk/bind
- tk/bindtags
- tk/caret
- tk/choosecolor
- tk/choosedirectory
- tk/clipboard
- tk/console
- tk/destroy
- tk/dialog
- tk/event
- tk/focus
- tk/getopenfile
- tk/getsavefile
- tk/grab
- tk/grid
- tk/image
- tk/lower
- tk/messagebox
- tk/option
- tk/pack
- tk/place
- tk/popup
- tk/raise
- tk/scaling
- tk/update
- tk/useinputmethods
- tk/wait
- tk/windowingsystem
- tk/winfo
- tk/wm
- Options
- Extensions
- Changes
Many items support the notion of an dash pattern for outlines.
The first possible syntax is a list of integers. Each element represents the number of pixels of a line segment. Only the odd segments are drawn using the "outline" color. The other segments are drawn transparant.
The second possible syntax is a character list containing only 5 possible characters [.,-_ ]. The space can be used to enlarge the space between other line elements, and can not occur as the first position in the string. Some examples:
#:dash "." = #:dash '(2 4)
#:dash "-" = #:dash '(6 4)
#:dash "-." = #:dash '(6 4 2 4)
#:dash "-.." = #:dash '(6 4 2 4 2 4)
#:dash ". " = #:dash '(2 8)
#:dash "," = #:dash '(4 4)
The main difference of this syntax with the previous is that it it shape-conserving. This means that all values in the dash list will be multiplied by the line width before display. This assures that "." will always be displayed as a dot and "-" always as a dash regardless of the line width.
On systems which support only a limited set of dash patterns, the dash pattern will be displayed as the closest dash pattern that is available. For example, on Windows only the first 4 of the above examples are available. The last 2 examples will be displayed identically to the first one.