FWIW I looked at this comment in the getTabbedTextOffset method
// the length of the string measured as a whole may differ from
                // the sum of individual character lengths, for example if
// fractional metrics are enabled; and we must guard from this.

I am not really sure what the author was trying to say here.
Fractional Metrics is NOT the same thing as using floating point to measure width. You will need floating point for fractional metrics .. but that makes it a necessary condition,
not the same thing.

Also I looked at the rounding code

The logic for round==true seems to be trying to find the offset that is closest
to the target position, so it may be less, the same or greater.

For round=false, it is trying to find the largest offset that does not exceed it.

I am not sure who would use the true case, but at least we can be consistent
in using false in both cases.

+1

-phil.
-phil

On 6/10/18, 8:42 AM, Prasanta Sadhukhan wrote:


On 6/9/2018 3:53 AM, Philip Race wrote:
The oddity about using round=true at line 845 is the other case seems to be using round == false ?

I think round==false was intended for use with fractional metrics but it is not clear.

Seems logical.
Modified webrev
http://cr.openjdk.java.net/~psadhukhan/8199441/webrev.03/

Regards
Prasanta
-phil

On 6/7/18, 4:12 AM, Prasanta Sadhukhan wrote:
Updated webrev (as you pointed) to modify WrappedPlainView to use FP version

http://cr.openjdk.java.net/~psadhukhan/8199441/webrev.02/

I have used "round" to be true as
public static final int getTabbedTextOffset(Segment s, FontMetrics metrics, int x0, int x, TabExpander e,
                                             int startOffset) {
uses "round" value as true.
I did not find any other usage of this int version of the API other than WrappedPlainView.

static final int getTabbedTextOffset(View view, Segment s, FontMetrics metrics,
                                         int x0, int x, TabExpander e,
                                         int startOffset,
                                         int[] justificationData) {}
is used in GLyphPainter1#viewToModel but it was not needed for this particular issue so I have not changed it for now.

Regards
Prasanta
On 6/7/2018 3:33 AM, Phil Race wrote:
This is changing the internals of getTabbedTextOffset and using FP regardless
of whether useFPAPI is true. This is not what I said.

I wrote that you should call the FP version directly.

Look at this
---
     * @deprecated replaced by
* {@link #getTabbedTextOffset(Segment, FontMetrics, float, float,
     *                                 TabExpander, int, boolean)}
     */
    @Deprecated(since = "9")
public static final int getTabbedTextOffset(Segment s, FontMetrics metrics, int x0, int x, TabExpander e,
                                             int startOffset) {
return getTabbedTextOffset(s, metrics, x0, x, e, startOffset, true);
----
If we had wanted what you proposed in the first webrev and I think
this one is effectively same, we'd have altered the behaviour to and not
deprecated and added new API

So whatever code in our L&F is currently calling

getTabbedTextOffset(Segment s,
                    FontMetrics metrics,
                    int x0, int x, TabExpander e,
                    int startOffset)

should instead call

getTabbedTextOffset(Segment s,
                    FontMetrics metrics,
                    float x0, float x, TabExpander e,
                    int startOffset,
                    boolean round)

I am not sure if round should be true or false but calling the float version is the key.

This (and no other change needed) does the trick for me :

--- a/src/java.desktop/share/classes/javax/swing/text/WrappedPlainView.java +++ b/src/java.desktop/share/classes/javax/swing/text/WrappedPlainView.java
@@ -360,11 +360,11 @@
         int currentWidth = getWidth();
         if (wordWrap) {
             p = p0 + Utilities.getBreakLocation(segment, metrics,
- tabBase, tabBase + currentWidth,
+ (float)tabBase, (float)(tabBase + currentWidth),
                                                 this, p0);
         } else {
             p = p0 + Utilities.getTabbedTextOffset(segment, metrics,
- tabBase, tabBase + currentWidth,
+ (float)tabBase, (float)(tabBase + currentWidth),
                                                    this, p0, false);
         }
         SegmentCache.releaseSharedSegment(segment);
@@ -847,8 +847,8 @@
Segment segment = SegmentCache.getSharedSegment();
                         loadText(segment, p0, p1);
int n = Utilities.getTabbedTextOffset(segment, metrics,
-                                                   alloc.x, x,
- WrappedPlainView.this, p0);
+ (float)(alloc.x), (float)x,
+ WrappedPlainView.this, p0, false);
SegmentCache.releaseSharedSegment(segment);
                         return Math.min(p0 + n, p1 - 1);
                     }

I may have missed something else but to verify I downloaded and used your test, which BTW has DOS line-endings !

-phil.

On 06/06/2018 12:04 AM, Prasanta Sadhukhan wrote:


On 5/9/2018 12:41 AM, Phil Race wrote:
I am not sure this is the right fix.
If the intention had been to change all calls to getTabbedTextOffset() to use the FP API it would have just been changed .. rather than adding a new API that provides
the option to specify whether to use FP.

So perhaps the problem is that internal code needs to be updated to call the FP
version directly ..
I have updated the internal code to use the FP version directly
http://cr.openjdk.java.net/~psadhukhan/8199441/webrev.01/
There are no new regressions in jtreg and jck tests.

Regards
Prasanta
I'd like to read https://bugs.openjdk.java.net/browse/JDK-8168992 to see what was said there but JBS just went down for 5 hours maintenance ..

-phil.

On 05/07/2018 11:54 PM, Prasanta Sadhukhan wrote:
Hi Sergey,

I have run javax/swing/text jtreg and jck tests and did not observe any regressions.

Regards
Prasanta
On 4/28/2018 5:38 AM, Sergey Bylokhov wrote:
Hi, Prasanta.
Please confirm that you run related jck/reg tests.

On 26/04/2018 23:52, Prasanta Sadhukhan wrote:
Hi All,

Please review a fix for an issue where it is seen that,
with a screen resolution higher than 100% and then clicking in a JTextArea having setLineWrap(true) set, the caret (insertion point) is not aligned with the cursor.

The issue seems to stem from the fact that caret position calculation in DefaultCaret class utilises API that uses integer calculation than floating point calculations.
The code flow as seen is
DefaultCaret#positionCaret=>BasicTextUI#viewToModel=>BoxView.viewToModel=>CompositeView#viewToModel=>WrappedPlainView#viewToModel=>Utilities.getTabbedOffset Now, getTabbedOffset utilises FontMetrics.charsWidth() which uses integer arithmetic to get the caret position. The same getTabbedOffset uses Font.getStringBounds() which uses floating point arithmetic via Rectangle2D.Float.

Proposed fix is to make sure getTabbedOffset uses floating point calculations by using getStringBounds() instead of charsWidth() so that it calculates the character width(s) of text present in JTextArea in floating point to align the caret.

Bug: https://bugs.openjdk.java.net/browse/JDK-8199441
webrev: http://cr.openjdk.java.net/~psadhukhan/8199441/webrev.00/

Regards
Prasanta








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