Description Doug M 2010-07-12 18:23:31 EDT

Created attachment 174109 [details]
Demonstrates problem.

We are attempting to align text drawn directly in Composite with text drawn in a Text control by drawing the text and placing the control at the same y position. Their vertical alignment varies with the point size, as the Text control seems to "randomly" add space above its Text. Therefore at some point sizes, alignment is perfect, while at others the Text's text is lowered by 1-2 pixels.

StyledText's alignment is always exactly right.

I think that computeTrim is supposed to report the unused area around a control, however it always indicates no trim, and getClientRect is the same as the Text's bounds. Likewise, the information returned by FontMetrics getHeight, getAscent, and getDescent reveals no consistency to the misalignment. (At least I can't deduce any.)

I am developing a complex text-based client that needs to draw editable text, with text and graphic decorations in precise relationship to the Text. So I need to be able to tell exactly where Text draws its text (in relation to the Text or its parent), either by it's being consistent, or the API revealing this information.

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Textalign attachment draws Courier text in a Composite's PaintListener at the same vertical position as a Text. It also draws a horizontal line at the text position. The Bigger and Smaller buttons adjust the font size. Note that for some sizes the text is not aligned.

Values for the bounds, trim, and client rectangles, and font height, ascent, and descent are printed to Output.

Change Text to StyledText to see the alignment work always.