Module #04.02.03.03 : Inquire text extent

DESCRIPTION: This module tests the behavior of the <inquire text
extent> function.  In the SR's, all references to text attributes
refer to the parameters of the function, not to elements within
the CSS or to text bundle tables.

SEMANTIC REQUIREMENTS:

*** *** ***   Input parameters   *** *** ***

SR1.  Text font specifies which font of the given workstation type
is used to generate the virtual text string from which the text
extent rectangle is computed.

SR2.  For all text fonts, a character body in TLC is a rectangle
generally surrounding the character, aligned such that the top,
cap, half, base, and bottom lines are all parallel to the TLC
x-axis and the left, centre, and right lines are all parallel to
the TLC y-axis.

SR3.  All text fonts are either monospaced or proportionately
spaced.  All character bodies within a monospaced font have the
same font nominal height and the same font nominal width.  All
character bodies within a proportionately spaced font have the
same font nominal height.

SR4.  Text font 1 is monospaced.

SR5.  For text font 1, the results are workstation independent.

SR6.  The magnitude of the character expansion factor specifies
the amount by which the font nominal width/height ratio of
individual TLC character bodies is multiplied to yield the actual
TLC width/height ratio.

SR7.  Character spacing specifies the TLC distance (positive) or
overlap (negative) between adjacent character bodies, expressed
in units of the font nominal character height.

SR8.  The magnitude of the character height specifies, in TLC, the
font nominal height (from baseline to capline) of a capital
letter.

SR9.  The font nominal width in TLC of a character within a
text primitive is given by the font's intrinsic width to height
ratio for that character times the magnitude of the character
height.

SR10.  The text path specifies the writing direction within the
TLC text plane for the text string (i.e. the direction in which
successive character bodies are appended) as follows: RIGHT:
positive x-axis, LEFT: negative x-axis, UP: positive y-axis,
DOWN: negative x-axis.

SR11.  The text alignment specifies which horizontal and vertical
location within the text rectangle is to coincide with the TLC
origin by shifting the text rectangle within the text plane.  For
all text paths, alignments LEFT, RIGHT, BOTTOM, and TOP refer to
the left, right, bottom, and top edges of the rectangle, and
CENTRE refers to the horizontal location midway between the left
and right edges.  For horizontal text paths, CAP, HALF, and BASE
refer to the capline, halfline, and baseline of the whole text
string.  For vertical text paths, CAP refers to the capline of
the topmost character, BASE refers to the baseline of the
bottommost character, and HALF refers to the vertical location
midway between the halflines of the topmost and bottommost
characters.

SR12.  The effect of NORMAL as the horizontal or vertical
component of text alignment is equivalent to one of the other
defined values for text alignment and depends on text path as
follows:
text path  |  (horizontal, vertical)
-----------+------------------------
RIGHT      |  (LEFT,       BASE)
LEFT       |  (RIGHT,      BASE)
UP         |  (CENTRE,     BASE)
DOWN       |  (CENTRE,     TOP)

*** *** ***   Implicit text attributes   *** *** ***

SR13.  In <inquire text extent>, the implicit text position is
(0,0), the implicit character up vector is (0,1), and the
implicit text precision is STROKE.

SR14.  For text precision = STROKE, text is displayed with all
text aspects applied exactly.

*** *** ***   Output parameters   *** *** ***

SR15.  For horizontal text paths, the left (right) edge of the
text extent rectangle (expressed in TLC) coincides with the left
(right) edge of the leftmost (rightmost) character of the text
string, as it would be generated for the implicit and specified
attributes and workstation type.   Its top and bottom edges
coincide with the top and bottom edges of the character bodies.

SR16.  For vertical text paths, the top (bottom) edge of the text
extent rectangle (expressed in TLC) coincides with the top
(bottom) edge of the topmost (bottommost) character of the text
string, as it would be generated for the implicit and specified
attributes and workstation type.  Its width is the width of the
widest character body within the font as determined by character
height and as modified by the character expansion factor
parameter.  Its left and right edges are equidistant from the
centreline along which the character bodies are aligned.

SR17.  The location of the concatenation point (CP), expressed in
TLC, for zero character spacing depends on text path as follows:
-------------------------------------------------------------------
text path  |  horizontal-CP               vertical-CP
-----------+-------------------------------------------------------
RIGHT      |  right edge of text extent   text-position (zero)
LEFT       |  left edge of text extent    text-position (zero)
DOWN       |  text-position (zero)        bottom edge of text extent
UP         |  text-position (zero)        baseline of next character

SR18.  The location of the concatenation point includes character
spacing after the last character in text string in the direction
of the TEXT PATH.

  Functions ---
  : pqtxx   <inquire text extent>
 
  Data Structures ---
  ...  workstation_description_table
  6.12  ...  text_entry
  6.12.1  ...  text_facilities
  6.12.1.1  ...  number_of_text_font_and_precision_pairs
  6.12.1.2  ...  list_of_text_font_and_precision_pairs
  6.12.1.2.1  ...  text_font_and_precision_pair
 
SEMANTIC CROSS-REFERENCES:
  02.03.03/SR15

LOCAL SUBROUTINES: The programs in this module use the following
subroutines:

CHTXRC: Computes expected results for various parameter values
which affect the size of the text extent rectangle and the
concatenation point.  Computation is based on deviation from
nominal width and length of entire string.  Therefore, CHTXRC may
be used for non-monospaced fonts.

CHMONO: Computes expected results for various parameter values
which affect the size of the text extent rectangle and the
concatenation point.  Computation is based on deviation from
nominal character size in text path dimension and thickness of
entire string in other dimension.  Therefore, CHMONO is valid
only when every character in the string has the same size.

TXCOMP: Compares actual and expected values for results of
<inquire text extent> and reports results in two logical
variables.  TXCOMP tests both text paths for the given
orientation, i.e. LEFT and RIGHT for horizontal, UP and DOWN
for vertical.


PROGRAM 1: Text font in <inquire text extent>

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PROGRAM 2: Text rectangle size and concatenation point for horizontal text orientation

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PROGRAM 3: Text rectangle size and concatenation point for vertical text orientation

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PROGRAM 4: Text alignment

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PROGRAM 5: Text extent results derived from nominal character sizes

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PROGRAM 6: Appearance of text extent rectangle

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End of documentation for 04.02.03.03