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

[Philip Race]

On 8/24/16, 9:45 AM, Alexander Scherbatiy wrote:
> On 17/08/16 22:49, Phil Race wrote:
>> Sorry, but I have had some trouble trying to picture this.
>> If the caret is between "b" and "c", being off by a fractional value 
>> seems
>> unlikely to make it jump to between "a" and "b".
>> It might now "round" to somewhere in the trailing pixel of "b" but 
>> nowhere
>> near the leading edge.
>   I suppose yes.
>
>   Another case is when a caret is in the center of the "b". In this 
> case it can be moved to another character if fractional values are not 
> taken into account. However, may be it does not matter which character 
> "a" or "c" would be chosen because they have nearly the same distance 
> to the center of the "b".

Indeed. And I think that is no different than today that "in the middle" 
means
it is 50:50 which way it goes with integers too.
Also unless this position was set by some code that just picked a position
out thin air, I would expect this to always be "between" the characters as
a result of normal calculation of the caret.

-phil.
>
> Thanks,
> Alexandr.
>
>>
>> -phil.
>>
>>
>> On 08/11/2016 09:55 AM, Alexandr Scherbatiy wrote:
>>>
>>> I am sorry. The JTextComponent.viewToModel(Point) method returns the 
>>> closest location for the provided point. If the caret position is 
>>> N.25 the distance to the right character is 0.25 and to the left one 
>>> is greater than 0.75. Even in for the worst case the distance to the 
>>> right character is less than 1 and to the left is greater than 1 
>>> (suppose a character width is greater than 1). For the provided 
>>> cases the caret should always be placed in the proper closest location.
>>>
>>> There is just a question could a user just compare the provided 
>>> magic caret position (which coordinates are rounded) with the result 
>>> of rectangle from the method JTextComponent.modelToView2(position) 
>>> which returns the floating point positions. So for the same position 
>>> the rounded point can be (N, y) and the rectangle can have bounds 
>>> (N.25, y, w, h). Comparing these results can lead that the magic 
>>> caret point does not belong to the provided rectangle but it is 
>>> definitely that the x coordinate of this rectangle is the closest 
>>> one to this point.
>>>
>>> By the way, I can merge the added JTextComponent.modelToView2D(int 
>>> pos)/viewToModel2D(Point2D pt) public methods with the fix for the
>>>   8156217 Selected text is shifted on HiDPI display
>>>     http://cr.openjdk.java.net/~alexsch/8156217/webrev.04/
>>>
>>> Thanks,
>>> Alexandr.
>>>
>>> On 8/10/2016 5:22 PM, Alexandr Scherbatiy wrote:
>>>>
>>>> Suppose there is a text area with two lines with the same text:
>>>> abcdefghij
>>>> abcdefghij
>>>>
>>>> The char 'c' on the fist line has offset 2 and some coordinates 
>>>> (x1, y1) where x1 can have a floating point values like 21.25.
>>>> The char 'c' on the second line has offset 13 and coordinates (x2, 
>>>> y2) where x2 is equal to x1.
>>>>
>>>> Setting the caret to the first 'c' character sets the magic caret 
>>>> position to  (round (x1), round (y1)) position.
>>>> Pressing the arrow down key calculates the new  y position and uses 
>>>> the x position from the magic caret position which is round(21.5) = 
>>>> 21.
>>>> Now the new offset can be calculated as 
>>>> textComponent.viewToModel(new Point(21, newY)) which returns offset 
>>>> 12 for char 'b' on the second line instead the offset 13 for char 'c'.
>>>>
>>>> Thanks,
>>>> Alexandr.
>>>>
>>>> On 8/9/2016 11:32 PM, Philip Race wrote:
>>>>> But characters are of varying width. Being on the "20th" char on 
>>>>> line N
>>>>> may mean being on the "25th" on line N+1.
>>>>>
>>>>> So I am claiming this is nothing new and we really do not need do 
>>>>> anything here.
>>>>>
>>>>> -phil.
>>>>>
>>>>> On 8/9/16, 1:06 PM, Alexandr Scherbatiy wrote:
>>>>>> 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.
>>>>>>>
>>>>>>
>>>>
>>>
>>
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