[netbeans] branch master updated: [NETBEANS-346] Tabs, characters, and the right Margin don't line up

[sk...@apache.org]

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skygo pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/netbeans.git


The following commit(s) were added to refs/heads/master by this push:
     new d2e893c  [NETBEANS-346] Tabs, characters, and the right Margin don't line up
     new 1a8548d  Merge pull request #2076 from eirikbakke/NETBEANS-346
d2e893c is described below

commit d2e893c3b30611beb823e7d7c758b90acd41f6be
Author: Eirik Bakke <eb...@ultorg.com>
AuthorDate: Mon Apr 13 17:36:46 2020 -0400

    [NETBEANS-346] Tabs, characters, and the right Margin don't line up
---
 .../org/netbeans/modules/editor/lib2/view/FontInfo.java    | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/ide/editor.lib2/src/org/netbeans/modules/editor/lib2/view/FontInfo.java b/ide/editor.lib2/src/org/netbeans/modules/editor/lib2/view/FontInfo.java
index f188a2f..e9185d7 100644
--- a/ide/editor.lib2/src/org/netbeans/modules/editor/lib2/view/FontInfo.java
+++ b/ide/editor.lib2/src/org/netbeans/modules/editor/lib2/view/FontInfo.java
@@ -91,8 +91,18 @@ final class FontInfo {
         TextLayout rowHeightTextLayout = new TextLayout("A_|B", renderFont, frc);
         // Round the ascent to eliminate long mantissa without any visible effect on rendering.
         updateRowHeight(rowHeightTextLayout, rowHeightCorrection);
-        // Ceil fractions to whole numbers since this measure may be used for background rendering
-        charWidth = (float) Math.ceil(defaultCharTextLayout.getAdvance());
+        /* We originally did Math.ceil() when setting charWidth, but this was the cause of NETBEANS-346,
+        where the end-of-line marker (SimpleValueNames.TEXT_LIMIT_WIDTH) would appear in the wrong
+        position due to rounding errors, and similar misalignments in tabs vs. spaces, on certain editor
+        zoom levels. This was observed on Java 9 or above on both Windows and MacOS. Java 9 saw many
+        changes in font metrics implementations, including a new font shaping engine (HarfBuzz) and
+        fractional HiDPI support. Avoiding Math.ceil fixes the problem. The original Math.ceil was
+        introduced by Miloslav Metelka on 2011-08-18, with a comment "Ceil fractions to whole numbers
+        since this measure may be used for background rendering" in the commit titled "Improve
+        AnnotationView performance" for the similarly titled BugZilla bug #201102. So the Math.ceil was
+        intended to be an optimization rather than fixing a correctness bug, and it seems safe to remove
+        it. */
+        charWidth = defaultCharTextLayout.getAdvance();
         LineMetrics lineMetrics = renderFont.getLineMetrics(defaultCharText, frc);
         underlineAndStrike[0] = lineMetrics.getUnderlineOffset() * rowHeightCorrection;
         underlineAndStrike[1] = lineMetrics.getUnderlineThickness();


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