widthshow

1.1. Syntax

cx cy char string widthshow → -

1.2. Stack Effects

Before:

cx cy char string

After:

(empty)

1.3. Description

widthshow paints the characters of string in a manner similar to show. But while doing so, widthshow adjusts the width of each occurrence of the character char by adding cx to its x width and cy to its y width, thus modifying the spacing between it and the next character.

The char parameter is an integer used as a character code. This operator enables fitting a string of text to a specific width by adjusting the width of all occurrences of some specific character, such as the space character.

1.4. Parameters

cx (number) : Amount to add to x width of target character

cy (number) : Amount to add to y width of target character

char (integer) : Character code to adjust (typically space = 32 or 8#040)

string (string) : The text to display

1.5. Character Code Interpretation

For base fonts: : char is simply an integer in the range 0-255 compared to successive elements of string

For composite fonts: : char is compared to an integer computed from the font mapping algorithm. The font number f and character code c selected by the algorithm are combined: - For FMapType 4 and 5: (f × 128) + c - For other FMapType values: (f × 256) + c

1.6. Examples

1.6.1. Adjusting Space Character Width

/Helvetica findfont 12 scalefont setfont

14 60 moveto (Normal spacing) show
14 46 moveto 6 0 32 (Wide word spacing) widthshow
% 32 is ASCII code for space

1.6.2. Using Octal Character Code

/Helvetica findfont 12 scalefont setfont

100 700 moveto
6 0 8#040 (Wide word spacing) widthshow
% 8#040 is octal for space (32 decimal)

1.6.3. Justified Text with Space Adjustment

/justifyWithSpaces {  % string targetWidth justifyWithSpaces -
  % Count spaces in string
  0 exch
  { dup 32 eq { pop 1 add } { pop } ifelse } forall
  % Stack: targetWidth spaceCount

  dup 0 eq {
    % No spaces, just show
    pop pop show
  } {
    % Calculate space adjustment
    3 -1 roll              % spaceCount targetWidth string
    1 index stringwidth pop % Get current width
    sub exch div           % (targetWidth - currentWidth) / spaceCount
    0 exch 32              % cx=adjustment, cy=0, char=32
    4 -1 roll widthshow    % Apply
  } ifelse
} def

100 700 moveto
(This text will be justified) 400 justifyWithSpaces

1.6.4. Adjusting Multiple Character Types

% Adjust spaces first
100 100 moveto
3 0 32 (Text with wide spaces) widthshow

% For multiple character adjustments, cascade:
currentpoint moveto
2 0 65 (Adjust A character) widthshow  % Adjust 'A'

1.7. Errors

invalidaccess : Font or string has restricted access

invalidfont : Current font is not valid

nocurrentpoint : Current point is not defined

stackunderflow : Fewer than four operands on stack

typecheck : cx/cy not numbers, char not integer, or string not string

rangecheck : Character mapping goes out of bounds

1.8. Width Adjustment Formula

For each character c in the string:

if c == char:
  effectiveWidth(c) = characterWidth(c) + (cx, cy)
else:
  effectiveWidth(c) = characterWidth(c)

1.9. Common Character Codes

Character	Decimal	Octal
Space	32	8#040
Tab	9	8#011
Newline	10	8#012
Hyphen	45	8#055
Period	46	8#056

Character

Decimal

Octal

Space

32

8#040

Tab

9

8#011

Newline

10

8#012

Hyphen

45

8#055

Period

46

8#056

1.10. Use Cases

1.10.1. Word Spacing for Justification

/adjustSpaces {  % adjustment string adjustSpaces -
  0 exch 32 4 -1 roll widthshow
} def

100 700 moveto
5 (Widely spaced words) adjustSpaces

1.10.2. Em-Dash Adjustment

% Reduce space around em-dash (character 208 in some encodings)
/Helvetica findfont 12 scalefont setfont
100 100 moveto
-2 0 208 (Text—with—em-dashes) widthshow

1.10.3. Compensating for Printer Resolution

% Fine-tune spacing for specific output device
/deviceAdjust {
  % Get device resolution
  matrix defaultmatrix dtransform
  dup mul exch dup mul add sqrt  % Calculate DPI

  300 div  % Normalize to 300 DPI
  0 exch 32 4 -1 roll widthshow
} def

(Device-adjusted text) deviceAdjust

1.11. Advanced Techniques

1.11.1. Conditional Spacing

/conditionalSpacing {  % string conditionalSpacing -
  % Only adjust if string contains target character
  dup 32 search {
    % Contains space
    pop pop pop
    3 0 32 4 -1 roll widthshow
  } {
    % No spaces, use normal show
    show
  } ifelse
} def

1.11.2. Tracking (Typography)

% Letter spacing control for display type
/looseTracking {  % string looseTracking -
  % Add space to every character (including spaces)
  % This requires combining techniques
  dup stringwidth pop  % Original width
  1 index length 1 add 10 mul add  % Add 10 units per char
  2 div                % Center
  neg 0 rmoveto        % Adjust position
  1.5 0 32 4 -1 roll widthshow  % Wider spaces
} def

1.12. Performance Considerations

Slightly slower than show due to conditional width adjustment
Still benefits from font caching
More efficient than kshow for simple spacing needs
Character matching is done by simple integer comparison (fast)

1.13. Comparison with Other Spacing Operators

Operator Spacing Adjustment

Operator	Spacing Adjustment
`show`	None (uses character widths as-is)
`ashow`	Uniform adjustment to all characters
`widthshow`	Adjustment to specific character only
`awidthshow`	Both uniform and character-specific
`kshow`	Procedural control between each pair

show

None (uses character widths as-is)

ashow

Uniform adjustment to all characters

widthshow

Adjustment to specific character only

awidthshow

Both uniform and character-specific

kshow

Procedural control between each pair

1.14. See Also

show - Basic text painting
ashow - Show with uniform character spacing
awidthshow - Combine ashow and widthshow
kshow - Show with kerning procedure
cshow - Show with procedure per character
stringwidth - Calculate text width

1. widthshow