From 4f91e7a65f7bbbc0328e2e5e5c39492ccab869f0 Mon Sep 17 00:00:00 2001
From: Anton Tarasov <anton.tarasov@jetbrains.com>
Date: Tue, 12 Dec 2017 16:08:51 +0300
Subject: [PATCH] IDEA-183638 [fps] moving caret up/down leaves artifacts in
 the editor

---
 .../editor/impl/EditorComponentImpl.java      |  2 +-
 .../util/src/com/intellij/util/ui/JBUI.java   | 26 ++++++++++++++-----
 2 files changed, 20 insertions(+), 8 deletions(-)

diff --git a/platform/platform-impl/src/com/intellij/openapi/editor/impl/EditorComponentImpl.java b/platform/platform-impl/src/com/intellij/openapi/editor/impl/EditorComponentImpl.java
index a66ddb66b872..1e4068ac0912 100644
--- a/platform/platform-impl/src/com/intellij/openapi/editor/impl/EditorComponentImpl.java
+++ b/platform/platform-impl/src/com/intellij/openapi/editor/impl/EditorComponentImpl.java
@@ -230,7 +230,7 @@ public class EditorComponentImpl extends JTextComponent implements Scrollable, D
         UISettings.setupAntialiasing(gg);
       }
       gg.setRenderingHint(RenderingHints.KEY_FRACTIONALMETRICS, myEditor.myFractionalMetricsHintValue);
-      AffineTransform origTx = JBUI.alignToIntGrid(gg);
+      AffineTransform origTx = JBUI.alignToIntGrid(gg, true, false);
       myEditor.paint(gg);
       if (origTx != null) gg.setTransform(origTx);
     }
diff --git a/platform/util/src/com/intellij/util/ui/JBUI.java b/platform/util/src/com/intellij/util/ui/JBUI.java
index 032bfd6a4a74..25f840cefa9b 100644
--- a/platform/util/src/com/intellij/util/ui/JBUI.java
+++ b/platform/util/src/com/intellij/util/ui/JBUI.java
@@ -556,21 +556,24 @@ public class JBUI {
   }
 
   /**
-   * If the graphics has floating point scale transform, aligns the graphics to the integer coordinate grid,
+   * Aligns the x or/and y translate of the graphics to the integer coordinate grid if the graphics has fractional scale transform,
    * otherwise does nothing. This is used to avoid the rounding problem, see JRE-502.
    *
    * @param g the graphics to align
+   * @param alignX should the x-translate be aligned
+   * @param alignY should the y-translate be aligned
    * @return the original graphics transform when aligned, otherwise null
    */
-  public static AffineTransform alignToIntGrid(@NotNull Graphics2D g) {
+  public static AffineTransform alignToIntGrid(@NotNull Graphics2D g, boolean alignX, boolean alignY) {
     try {
       AffineTransform tx = g.getTransform();
-      double scaleX = tx.getScaleX();
-      double scaleY = tx.getScaleY();
-      boolean fpsTx = scaleX != (int)scaleX || scaleY != (int)scaleY;
-      if (fpsTx) {
+      if (isFractionalScale(tx)) {
+        double scaleX = tx.getScaleX();
+        double scaleY = tx.getScaleY();
         AffineTransform alignedTx = new AffineTransform();
-        alignedTx.translate((int)Math.ceil(tx.getTranslateX() - 0.5), (int)Math.ceil(tx.getTranslateY() - 0.5));
+        double trX = alignX ? (int)Math.ceil(tx.getTranslateX() - 0.5) : tx.getTranslateX();
+        double trY = alignY ? (int)Math.ceil(tx.getTranslateY() - 0.5) : tx.getTranslateY();
+        alignedTx.translate(trX, trY);
         alignedTx.scale(scaleX, scaleY);
         assert tx.getShearX() == 0 && tx.getShearY() == 0; // the shear is ignored
         g.setTransform(alignedTx);
@@ -583,6 +586,15 @@ public class JBUI {
     return null;
   }
 
+  /**
+   * Returns true if the transform matrix contains fractional scale element.
+   */
+  public static boolean isFractionalScale(AffineTransform tx) {
+    double scaleX = tx.getScaleX();
+    double scaleY = tx.getScaleY();
+    return scaleX != (int)scaleX || scaleY != (int)scaleY;
+  }
+
   public static class Fonts {
     @NotNull
     public static JBFont label() {