xgridfit 2.3-1 / usr / share / xml / xgridfit / utils / ff-functions.xgf

<?xml version="1.0" encoding="UTF-8"?>
<xgridfit xmlns="http://xgridfit.sourceforge.net/Xgridfit2">

  <!--
      The explanations of the FontForge functions are copied (with
      minimal editing for clarity in the present context) from the
      FontForge source file nowakowskittfinstr.c. That file contains
      the following notice:

      Copyright (C) 2000-2009 by
         George Williams, Michal Nowakowski & Alexey Kryukov

      Redistribution and use in source and binary forms, with or
      without modification, are permitted provided that the following
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      The name of the author may not be used to endorse or promote
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      THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY
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  -->

  <macro name="ff-position-point-in-blue-zone">
    <!--
	Position a point within a blue zone (given via cvt).  Note: in
	case of successful init of 'cvt' and 'prep' this function
	could be much simpler.
    -->
    <param name="pt"/>
    <param name="cv-of-blue"/>
    <push>pt cv-of-blue 0</push>
    <command name="CALL"/>
  </macro>

  <macro name="ff-position-point-relative">
    <!--
	Place given point relatively to previous, maintaining the
	minimum distance. Then call FPGM 12 to check if the point's
	gridfitted position is too far from its original position, and
	correct it, if necessary.
    -->
    <param name="pt"/>
    <push>pt 1</push>
    <command name="CALL"/>
  </macro>

  <macro name="ff-adjust-cv-at-low-res">
    <!--
	Below given ppem, substitute the width with cvt entry.  Leave
	the resulting width on the stack. Used as the first step in
	normalizing cvt stems, see normalize_stem().
    -->
    <param name="width"/>
    <param name="cv"/>
    <param name="ppem"/>
    <push>width cv ppem 2</push>
    <command name="CALL"/>
  </macro>

  <macro name="ff-round-no-less-than-one-pixel">
    <!--
	Round a stack element as a black distance, respecting minimum
	distance of 1px. This is used for rounding stems after width
	normalization. Often preceeded with SROUND, so finally sets
	RTG.  Leaves the rounded width on the stack.
    -->
    <param name="val"/>
    <push>val 3</push>
    <command name="CALL"/>
  </macro>

  <macro name="ff-position-stem-second-edge">
    <!--
	Position the second edge of a stem that is not normally
	regularized via cvt (but we snap it to cvt width below given
	ppem).  Vertical stems need special round state when not
	snapped to cvt (basically, they are shortened by 0.25px before
	being rounded).
    -->
    <param name="pt"/>
    <param name="cv"/>
    <param name="chg-rp0"/>
    <param name="ppem"/>
    <push>pt cv chg-rp0 ppem 4</push>
    <command name="CALL"/>
  </macro>

  <macro name="ff-is-vertical">
    <!--
	Determine if we are hinting vertically. The function is crude
	and it's use is limited to conditions set by SVTCA[].  Syntax:
	PUSHB_1 5 CALL; leaves boolean on the stack.
    -->
    <push>5</push>
    <command name="CALL"/>
  </macro>

  <macro name="ff-is-grayscale">
    <!--
	Check if we are hinting in grayscale.  CAUTION! Older FreeType
	versions lie if asked.
    -->
    <push>6</push>
    <command name="CALL"/>
  </macro>

  <macro name="ff-is-cleartype">
    <!--
	Check if we are hinting in cleartype.  CAUTION! FreeType
	doesn't support that, as subpixel filtering is usually done by
	higher level library.
    -->
    <push>7</push>
    <command name="CALL"/>
  </macro>

  <macro name="ff-interpolate-and-snap">
    <!--
	Interpolate a point between two other points and snap it to
	the grid.
    -->
    <param name="pt"/>
    <param name="ref-pt-a"/>
    <param name="ref-pt-b"/>
    <push>pt ref-pt-a ref-pt-b 8</push>
    <command name="CALL"/>
  </macro>

  <macro name="ff-link-serif-point">
    <!--
	Link a serif-like element edge to the opposite edge of the
	base stem when rounding down to grid, but ensure that its
	distance from the reference point is larger than the base stem
	width at least to a specified amount of pixels.
    -->
    <param name="min-dist"/>
    <param name="inner-pt"/>
    <param name="outer-pt"/>
    <push>min-dist inner-pt outer-pt 9</push>
    <command name="CALL"/>
  </macro>

  <macro name="ff-link-serif-point-conditional">
    <!--
	Depending from the hinting mode (grayscale or mono) set rp0
	either to pt1 or to pt2. This is used to link serif-like
	elements either to the opposite side of the base stem or to
	the same side (i. e.  left-to-left and right-to-right).
    -->
    <param name="pt2"/>
    <param name="pt1"/>
    <push>pt2 pt1 10</push>
    <command name="CALL"/>
  </macro>

  <macro name="ff-position-point-relative-no-min">
    <!--
	Similar to FPGM 1 (ff-position-point-relative), but places a
	point without maintaining the minimum distance.
    -->
    <param name="pt"/>
    <push>pt 11</push>
    <command name="CALL"/>
  </macro>

  <macro name="ff-shift-from-too-far">
    <!--
	Check if the gridfitted position of the point is too far from
	its original position, and shift it, if necessary. The
	function is used to place vertical stems, it assures almost
	linear advance width to PPEM scaling. Shift amount is capped
	to at most 1 px to prevent some weird artifacts at very small
	ppems. In cleartype mode, no shift is made at all.
    -->
    <param name="pt"/>
    <push>pt 12</push>
    <command name="CALL"/>
  </macro>

  <macro name="ff-interpolate-hstem-and-snap">
    <!--
	Interpolate a HStem edge's reference point between two other
	points and snap it to the grid. Then compare its new position
	with the ungridfitted position of the second edge. If the
	gridfitted point belongs to the bottom edge and now it is
	positioned above the top edge's original coordinate, then
	shift it one pixel down; similarly, if the interpolation
	resulted in positioning the top edge below the original
	coordinate of the bottom edge, shift it one pixel up.
    -->
    <param name="other-edge-ref-pt"/>
    <param name="pt"/>
    <param name="ref-pt-a"/>
    <param name="ref-pt-b"/>
    <push> other-edge-ref-pt pt ref-pt-a ref-pt-b 13</push>
    <command name="CALL"/>
  </macro>

  <macro name="ff-link-points-no-min">
    <!--
	Link two points using MDRP without maintaining the minimum
	distance. In antialiased mode use rounding to double grid for
	this operation, otherwise ensure there is no distance between
	those two points below the given PPEM (i. e.  points are
	aligned). The function is used for linking nested stems to
	each other, and guarantees their relative positioning is
	preserved in the gridfitted outline.
    -->
    <param name="ppem"/>
    <param name="ref-pt"/>
    <param name="base-pt"/>
    <push>ppem ref-pt base-pt 14</push>
    <command name="CALL"/>
  </macro>

  <macro name="ff-position-point-relative-preserve-counter">
    <!--
	Similar to FPGM 1 (ff-position-point-relative), but used to
	position a stem relatively to the previous stem preserving the
	counter width equal to the distance between another pair of
	previously positioned stems. Thus it serves nearly the same
	purpose as PS counter hints.
    -->
    <param name="master-counter-start-pt"/>
    <param name="master-counter-end-pt"/>
    <param name="current-counter-start-pt"/>
    <param name="current-counter-end-pt"/>
    <param name="ppem"/>
    <push>
      master-counter-start-pt
      master-counter-end-pt
      current-counter-start-pt
      current-counter-end-pt
      ppem
      15
    </push>
    <command name="CALL"/>
  </macro>

  <macro name="ff-position-point-relative-alt">
    <!--
	Same as FPGM 1 (ff-position-point-relative), but calls FPGM 18
	rather than FPGM 12 and thus takes 3 arguments.
    -->
    <param name="ref-pt"/>
    <param name="pt"/>
    <push>ref-pt pt 16</push>
    <command name="CALL"/>
  </macro>

  <macro name="ff-position-point-relative-no-min-alt">
    <!--
	Same as FPGM 11 (ff-position-point-relative-no-min), but calls
	FPGM 18 rather than FPGM 12 and thus takes 3 arguments.
    -->
    <param name="ref-pt"/>
    <param name="pt"/>
    <push>ref-pt pt 17</push>
    <command name="CALL"/>
  </macro>

  <macro name="ff-shift-from-too-far-alt">
    <!--
	This is a special version of FPGM 12 (ff-shift-from-too-far),
	used when the counter control is enabled but doesn't directly
	affect the stem which is going to be positioned. Unlike FPGM
	12, it doesn't just attempt to position a point closely enough
	to its original coordinate, but also checks if the previous
	stem has already been shifted relatively to its "ideal"
	position FPGM 12 would determine. If so, then the desired
	point position is corrected relatively to the current
	placement of the previous stem.
    -->
    <param name="ref-pt"/>
    <param name="pt"/>
    <push>ref-pt pt 18</push>
    <command name="CALL"/>
  </macro>

  <macro name="ff-position-point-on-diagonal">
    <!--
	Used to align a point relatively to a diagonal line, specified
	by two other points. First we check if the point going to be
	positioned doesn't deviate too far from the line in the
	original outline. If the deviation is small enough to neglect
	it, we use ALIGNRP to position the point, otherwise MDRP is
	used instead. We can't just always use MDRP, because this
	command may produce wrong results at small PPEMs, if the
	original and gridfitted coordinates of the line end points
	specify slightly different unit vectors.
    -->
    <param name="pt"/>
    <param name="diag-start-pt"/>
    <param name="diag-end-pt"/>
    <push>pt diag-start-pt diag-end-pt 19</push>
    <command name="CALL"/>
  </macro>

  <macro name="ff-compute-projection-vector-adjustments">
    <!--
	Compute adjustments for X and Y components of projection
	vector, for aspect ratios different than 1:1, and store them
	in storage[0] and storage[1] respectively.
    -->
    <push>20</push>
    <command name="CALL"/>
  </macro>

  <macro name="ff-adjust-aspect-ratio-before-setting-vector">
    <!--
	Compute adjustments for X and Y components of projection
	vector, for aspect ratios different than 1:1, and store them
	in storage[0] and storage[1] respectively.
    -->
    <param name="x"/>
    <param name="y"/>
    <push>x y 21</push>
    <command name="CALL"/>
  </macro>

</xgridfit>