ashow

1.1. Syntax

ax ay string ashow → -

1.2. Stack Effects

Before:

ax ay string

After:

(empty)

1.3. Description

ashow paints the characters of string in a manner similar to show. But while doing so, ashow adjusts the width of each character shown by adding ax to the character’s x width and ay to its y width, thus modifying the spacing between characters.

The numbers ax and ay are x and y displacements in the user coordinate system, not in the character coordinate system. This operator enables a string of text to be fitted to a specific width by adjusting all the spaces between characters by a uniform amount.

1.4. Parameters

ax (number) : Amount to add to each character’s x width

ay (number) : Amount to add to each character’s y width

string (string) : The text to display

1.5. Examples

1.5.1. Wide Character Spacing

/Helvetica findfont 12 scalefont setfont

14 61 moveto (Normal spacing) show
14 47 moveto 4 0 (Wide spacing) ashow

1.5.2. Tight Character Spacing

/Helvetica findfont 12 scalefont setfont

100 700 moveto (Normal) show
100 685 moveto -1 0 (Tight) ashow  % Reduce spacing by 1 unit

1.5.3. Fitting Text to Width

/fitText {  % string targetWidth fitText -
  % Calculate adjustment needed
  1 index stringwidth pop  % Get current width
  1 index exch sub         % targetWidth - currentWidth
  2 index length 1 sub     % Number of spaces between chars
  div                      % Adjustment per space
  0 3 -1 roll ashow        % Apply adjustment
} def

(Hello World) 200 fitText

1.5.4. Vertical Spacing Adjustment

% Add vertical spacing (unusual but possible)
/Helvetica findfont 12 scalefont setfont
100 700 moveto
0 -2 (Descending text) ashow
% Each character shifts down by 2 units

1.6. Errors

invalidaccess : Font or string has restricted access

invalidfont : Current font is not valid

nocurrentpoint : Current point is not defined before ashow

stackunderflow : Fewer than three operands on stack

typecheck : ax or ay is not a number, or string is not a string

1.7. Width Calculation

For each character c in the string, the effective width becomes:

effectiveWidth(c) = characterWidth(c) + (ax, ay)

Total current point displacement:

totalDisplacement = Σ(characterWidth(c) + (ax, ay))
                  = Σ characterWidth(c) + n × (ax, ay)

where n is the string length.

1.8. Comparison with show

% These are equivalent:
100 100 moveto (ABC) show

100 100 moveto 0 0 (ABC) ashow  % Zero adjustment

1.9. Use Cases

1.9.1. Justified Text

/justifyLine {  % string lineWidth justifyLine -
  exch dup stringwidth pop     % Get current width
  3 -1 roll exch sub          % Calculate extra space
  1 index length 1 sub div    % Divide by num spaces
  0 exch 3 -1 roll ashow      % Apply uniform spacing
} def

(This text is justified) 400 justifyLine

1.9.2. Letter Spacing Control

% Loose letter spacing for headings
/Heading {
  /Helvetica-Bold findfont 18 scalefont setfont
  2 0 3 -1 roll ashow
} def

100 700 moveto (WIDE HEADING) Heading

1.9.3. Compensating for Transformations

% When CTM is scaled, adjust spacing
gsave
  2 1 scale         % Different x and y scale
  /Helvetica findfont 12 scalefont setfont
  100 100 moveto
  1 0 (Adjusted) ashow  % Compensate for scaling
grestore

1.10. Performance Notes

ashow is slightly slower than show due to spacing calculations
Character caching still applies
For uniform spacing of all text, set once and use show
For spacing only specific characters, use widthshow instead

1.11. Advanced Usage

1.11.1. Dynamic Spacing Based on Content

/adaptiveShow {  % string adaptiveShow -
  dup length 10 lt {
    % Short strings: wide spacing
    3 0 3 -1 roll ashow
  } {
    % Long strings: normal spacing
    show
  } ifelse
} def

(Short) adaptiveShow
(This is a much longer string) adaptiveShow

1.12. See Also

show - Basic text painting
widthshow - Adjust specific character width
awidthshow - Combine ashow and widthshow
kshow - Show with kerning procedure
cshow - Show with procedure per character
stringwidth - Calculate text width
moveto - Set current point

1. ashow