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List:       openjdk-openjfx-dev
Subject:    Font Metrics (was TextField Document model)
From:       swpalmer () gmail ! com (Scott Palmer)
Date:       2012-10-28 5:00:38
Message-ID: CBEB37F3-E9AB-48DA-AD79-A1873DD68F81 () gmail ! com
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My only complaint is that I had to subclass the default TextFieldSkin and set the \
TextField to use my skin just to get at the FontMetrics that were in use on the \
TextField control. I had no intention of actually implementing a skin or changing the \
behaviour of the default skin. I just wanted to position a popup where the caret was. \
So yes FontMetrics has what I need, but it should be more accessible.

Scott

On 2012-10-28, at 12:25 AM, Felipe Heidrich <felipe.heidrich at oracle.com> wrote:

> 
> On Oct 26, 2012, at 8:18 AM, Richard Bair wrote:
> 
> > I think these are two distinct issues -- font metrics and locating glyph bounds \
> > within a string of text. FontMetrics I think is fairly straightforward -- Felipe \
> > what do you think? 
> 
> Yes,
> Here the basics
> Text text = new Text();
> text.setFont(Font.font("Helvetica", 24));
> System.out.println("Baseline:" + text.getBaselineOffset());
> Bounds bounds = text.getLayoutBounds();
> //text origin by default is relative to baseline
> System.out.println("Ascent " + -bounds.getMinY());
> System.out.println("Descent " + bounds.getMaxY());//including leading
> System.out.println("LineHeight " + bounds.getHeight());
> 
> If you dig in the internals a bit you will see a FontLoader class that returns a \
> FontMetrics object for a given Font, it has x-height and other properties in it. \
> Other metrics like average char width I don't think the user can ever get. I think \
> we could provide better API in this area. 
> 
> > For the other use case, actually knowing the glyph bounds is not enough \
> > (probably). The problem is, suppose that text you were looking for wrapped from \
> > one line to the next (letter wrapping instead of word wrapping, or maybe you were \
> > searching for a phrase rather than just a word). In this case you need to know \
> > the shape that would encompassing text from both lines (think: blue selection \
> > box). Even more challenging is BIDI and ligatures -- what if the text you \
> > searched for was only using part of a glyph due to ligatures? Or you have \
> > disjoint shape due to BIDI (selection is a good example of this again). 
> > Now, internally we use an impl on Text to get the shape based on a range of \
> > indexes into the Text, and this shape is then used to draw selection. In our \
> > quest to get rid of impl methods, I have wanted to see this get proper API \
> > treatment. Maybe we would have a TextMeasurement class, and Text node (and \
> > TextFlow) would return an instance of it and we could have a method on it that \
> > vends a shape. Once you have a shape you can set the fill, stroke, etc as you \
> > like. 
> 
> As Richard said, internally we have all the information, we just need to design a \
> proper API. In the meantime, have you looked at TextFieldSkin caretPosition() and \
> getCharacterBounds(), it is based on Text's private API but it is a bit  cleaner \
> and sounds like what you are looking for. Anyhow, TextFieldSkin is not part of the \
> public API so not sure if it is a better approach for you. 
> Felipe
> 


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