<Swing Dev> [9] Review request for 8163124 Add floating point API support to javax.swing.text.Caret

[Alexandr Scherbatiy]

On 8/9/2016 12:44 AM, Phil Race wrote:
> I was not familiar with this "magic caret" but from reading it seems 
> like it has just one use/purpose.
> In the event that someone has multi-line text that you can navigate 
> around with up/down arrow keys
> and that text has lines of varying length, you want a "preferred" 
> horizontal position for the caret
> to be remembered so the caret is placed at that position whenever the 
> line of text has a length
> greater than the caret position. Is there anything more to it than that ?
>
> Obviously the caret needs to be placed correctly in the context of the 
> text, so the precise position,
> even in an all-integer world, is not going to line up on every single 
> line, unless you have monospaced text.
> ie the "pixel" position is going to get converted into a position on 
> the leading or trailing edge of some glyph
>
> So I wonder, does adding float matter .. is the extra precision 
> valuable here ?
   It may depend on the rounding of a point position.
   Suppose there are two lines with the same text. The caret is on the 
first line can have x position N.25. Pressing down the arrow key can 
round it to the N and the caret can be set to a previous char on the 
second line.

   Thanks,
   Alexandr.

>
> -phil.
>
> On 08/04/2016 05:44 AM, Alexandr Scherbatiy wrote:
>>
>> Hello,
>>
>> Could you review the fix:
>>   bug: https://bugs.openjdk.java.net/browse/JDK-8163124
>>   webrev: http://cr.openjdk.java.net/~alexsch/8163124/webrev.00
>>
>>   The text position can have floating point value on HiDPI display. 
>> The Caret interface should be updated to allow use floating point 
>> positions.
>>
>>   The fix adds the following public API with floating point positions:
>>   javax.swing.text.Caret.getMagicCaretPosition2D()
>>   javax.swing.text.Caret.setMagicCaretPosition2D(Point2D p)
>>   javax.swing.text.JTextComponent.modelToView2D(int pos)
>>   javax.swing.text.JTextComponent.viewToModel2D(Point2D pt)
>>   javax.swing.text.ParagraphView.getClosestPositionTo(int pos, 
>> Position.Bias b, Shape a, int direction, Position.Bias[], int 
>> rowIndex, float x)
>>
>>
>>   The fix replaces 
>> Caret.getMagicCaretPosition()/setMagicCaretPosition(Point p) to 
>> Caret.getMagicCaretPosition2D()/setMagicCaretPosition2D(Point2D p) in 
>> all places
>>   except DefaultCaret because DefaultCaret extends Rectangle so its 
>> coordinates always have int values.
>>   I have filled a separated enhancement for this JDK-8163174 Add 
>> DefaultCaret2D which supports floating point API
>>
>>   To make a custom caret use floating point API it is also necessary 
>> that PlainView.modelToView() returns a rectangle with floating point 
>> values. It can be done after the fix
>>     JDK-8156217 Selected text is shifted on HiDPI display
>>   which implements Utilities.getTabbedTextWidth(Segment s, 
>> FontMetrics metrics, float x, TabExpander e, int startOffset) method.
>>   I have filled a separated issue on it:
>>     JDK-8163175 PlainView.modelToView() method should return Rectangle2D
>>
>>  Thanks,
>>  Alexandr.
>