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Positioning tool


A positioning lookup can be edited in the Positioning Tool. To start editing a positioning lookup, double click on it in the main project window or select it and press the 'Edit Lookup' button. This is by far the most complex tool in the box; the description below only provides a general description.

Substitution tool

Anchor attachment [reduced by 50%]


Lookup header

See the lookup header section for the Substitution Tool.


Lookup types

The type for the lookup has to be chosen before any data can be entered into the Positioning Tool. Below very brief notes on every lookup type follow.


Glyph positioner

This is the area where you can specify positioning operation by drag-and-dropping glyph and anchor images. You can also enter the adjustments or coordinates below in a little table, and they will be shown on the positioner.

For every operation you see several images on the positioner corresponding to the glyphs and anchors you can position. Te 'inactive' shapes that cannot be positioned are displayed in gray. Also on the positioner three lines indicate correspondingly the font ascender, base line and descender. It is advisable that positioning operations not cross ascender and descender boundaries. In the left-bottom corner of the Positioner you can see a small 'preview' or the result of the positioning at a smaller size. You can choose the size right below the preview.


Single adjustment

Allows you to adjust positions of single glyphs. Most useful when used in a contextual fashion. Glyphs: enter names of glyphs to be positioned into the list on the right. Glyphs groups can be used; all glyphs in the group (in one line) will receive the same treatment (the same adjustments to their positions). You cannot repeat the same glyph twice in different lines.

Positioning: select a glyph or glyph group. In the positioner, drag the glyph image to get the adjustment operation you need. Drag the tall 'width anchor' to enter adjustments to the advance width.

If multiple glyphs are entered on the simple line in the glyph list, you can choose different shapes from the drop-down list below to see how your positioning operation affects each glyph on the list.


Pair adjustment

Pair adjustment

Pair adjustment [reduced by 50%]

Allows you to position pairs of glyphs. Similar to single adjustment except that now there are two lists of glyphs, the first glyphs and the second glyphs.

Each pair of entries, one form the first glyph list and one form the second glyph list, gets to be adjusted individually. As with single adjustment, if a glyph group is has been used, all glyphs form the group get the same treatment and the same positioning.


Anchor attachment

Substitution tool

Anchor attachment [reduced by 50%]

This option allows you to define Mark-To-Base, Mark-To-Mark and Mark-To-Ligature lookups. The actual lookup type is defined by the type of glyphs used. You cannot mix different glyph types in one lookup.

Next to the mark you enter the anchor name that identifies the anchor at which it has to be positioned. One glyph can have any number of different anchors (having different names). If two marks share the same position relative to the base glyph, they can use the same anchor name. Defining Mark-To-Base Lookups: you enter a list of bases in the first glyph list and a list of marks in the second list. After selecting one entry from each list you can position the mark and the anchor point in the positioner.

If you used glyph groups in the base or mark list, you can choose a particular glyph to work with from drop-down boxes above the positioner. Please note that glyphs in one groups do NOT share the same positioning values in this case. However, you may apply one anchor position to all of the glyphs in a group by clicking on 'all 1st same' or 'all 2nd same' button.

Note: when you move the anchor point, if affects both the base anchor and the mark anchor. You can lock one of the two anchors to make sure you are only changing the other. (see below)

Note: mark values are global and shared between lookups. E.g. if two different lookups use the same anchor named 'TopCenter' for positioning a top mark over letter 'A', changing one lookup may affect another. You can lock a base anchor is you don't want it changing and then fine-tune the position with the mark anchor, or vice versa.

Locking anchors: below the positioner, an option is provided to lock either the first of the second anchor (or both). An anchor that is locked cannot be (unintentionally) changed until it is explicitly unlocked. If another lookup uses this same anchor (which is identified by glyph ID and anchor name), it will appear locked in that lookup as well.

Defining Mark-To-Mark and Mark-To-Ligature Lookups: is similar to defining mark-to-base lookups. The only difference is that one gets to define positions for many anchors per ligature glyph instead of one per simple base glyph. (one anchor per component). The currently 'active' component is controlled by the component drop-down box above the positioner. The 'inactive' component anchors and marks are grayed out.


Cursive attachment

Cursive attachment is similar to anchor attachment. The anchor name is fixed to 'entry' for the second glyph, 'exit' for the first glyph. Used to define cursive positioning lookups.


Caret positioning

Does not compile in an OTL lookup and cannot be linked to a feature. All data from caret positioning operations are gathered to produce the GDEF data that is in turn used by OpenType Layout services to for measuring operations and caret placement.

Glyph list: defines what ligatures' caret positions are described. Only ligature glyphs can be entered.

Drag the tall 'caret' anchors to the right positions of carets inside ligatures. A ligature will have one less caret anchors than it's number of components. You can choose the 'active' anchor by manipulating the component field above the positioner.


Adding device corrections

By checking the 'Adjustment Mode' box one can enter the mode when all positioning changes affect the currently selected size only. The 'Adjust at this Size' checkbox shows whether there are adjustments for the selected size; these adjustments are always displayed on the little preview; checking 'Adjustment Mode' will also show them on the big positioner and allow you to change them.

Un-checking the 'Adjust at this Size' box clears adjustments for this size; clicking the ''Clear' button erases them for all sizes.


Defining contextual positioning

See 'Using Contexts' under the Substitution Tool section.



this page was last updated 13 April 2000
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Start | Project window | Glyph grid | Glyph group | GSUB | GPOS | Proofing | File | Samples
Microsoft Typography | Developer information | VOLT | VOLT release notes