8297449: Update JInternalFrame Metal Border code

Backport-of: 09629570f5d064dc2a5cd670de8d648156ac3991

Author: GoeLin

src/java.desktop/share/classes/javax/swing/plaf/metal/MetalBorders.java

@@ -65,6 +65,8 @@
 import sun.swing.StringUIClientPropertyKey;
 import sun.swing.SwingUtilities2;
 
+import static sun.java2d.pipe.Region.clipRound;
+
 /**
  * Factory object that can vend Borders appropriate for the metal L & F.
  * @author Steve Wilson
@@ -247,19 +249,6 @@ public static class InternalFrameBorder extends AbstractBorder implements UIReso
          */
         public InternalFrameBorder() {}
 
-        /**
-         * Rounds a double to the nearest integer. It rounds 0.5 down,
-         * for example 1.5 is rounded to 1.0.
-         *
-         * @param d number to be rounded
-         * @return the rounded value
-         */
-        private static int roundHalfDown(double d) {
-            double decP = (Math.ceil(d) - d);
-            return (int)((decP == 0.5) ?  Math.floor(d) :  Math.round(d));
-        }
-
-
         public void paintBorder(Component c, Graphics g, int x, int y,
                                 int w, int h) {
             Color background;
@@ -276,41 +265,50 @@ public void paintBorder(Component c, Graphics g, int x, int y,
                 shadow = MetalLookAndFeel.getControlInfo();
             }
 
-            Graphics2D g2d = (Graphics2D) g;
-            AffineTransform at = g2d.getTransform();
-            Stroke oldStk = g2d.getStroke();
-            Color oldColor = g2d.getColor();
+            AffineTransform at = null;
+            Stroke oldStk = null;
+            boolean resetTransform = false;
             int stkWidth = 1;
+            double scaleFactor = 1;
+
+            if (g instanceof Graphics2D g2d) {
+                at = g2d.getTransform();
+                scaleFactor = at.getScaleX();
+                oldStk = g2d.getStroke();
+
+                // if m01 or m10 is non-zero, then there is a rotation or shear
+                // skip resetting the transform
+                resetTransform = ((at.getShearX() == 0) && (at.getShearY() == 0));
 
-            // if m01 or m10 is non-zero, then there is a rotation or shear
-            // skip resetting the transform
-            boolean resetTransform = ((at.getShearX() == 0) && (at.getShearY() == 0));
+                if (resetTransform) {
+                    g2d.setTransform(new AffineTransform());
+                    stkWidth = clipRound(Math.min(at.getScaleX(), at.getScaleY()));
+                    g2d.setStroke(new BasicStroke((float) stkWidth));
+                }
+            }
 
             int xtranslation;
             int ytranslation;
             int width;
             int height;
 
             if (resetTransform) {
-                g2d.setTransform(new AffineTransform());
-                stkWidth = roundHalfDown(Math.min(at.getScaleX(), at.getScaleY()));
-
                 double xx = at.getScaleX() * x + at.getTranslateX();
                 double yy = at.getScaleY() * y + at.getTranslateY();
-                xtranslation = roundHalfDown(xx);
-                ytranslation = roundHalfDown(yy);
-                width = roundHalfDown(at.getScaleX() * w + xx) - xtranslation;
-                height = roundHalfDown(at.getScaleY() * h + yy) - ytranslation;
+                xtranslation = clipRound(xx);
+                ytranslation = clipRound(yy);
+                width = clipRound(at.getScaleX() * w + xx) - xtranslation;
+                height = clipRound(at.getScaleY() * h + yy) - ytranslation;
             } else {
-                width = w;
-                height = h;
                 xtranslation = x;
                 ytranslation = y;
+                width = w;
+                height = h;
             }
-            g2d.translate(xtranslation, ytranslation);
+            g.translate(xtranslation, ytranslation);
 
             // scaled border
-            int thickness = (int) Math.ceil(4 * at.getScaleX());
+            int thickness = (int) Math.ceil(4 * scaleFactor);
 
             g.setColor(background);
             // Draw the bulk of the border
@@ -319,17 +317,14 @@ public void paintBorder(Component c, Graphics g, int x, int y,
             }
 
             if (c instanceof JInternalFrame && ((JInternalFrame)c).isResizable()) {
-                // set new stroke to draw shadow and highlight lines
-                g2d.setStroke(new BasicStroke((float) stkWidth));
-
                 // midpoint at which highlight & shadow lines
                 // are positioned on the border
                 int midPoint = thickness / 2;
-                int offset = ((at.getScaleX() - stkWidth) >= 0 && stkWidth % 2 != 0) ? 1 : 0;
+                int offset = (((scaleFactor - stkWidth) >= 0) && ((stkWidth % 2) != 0)) ? 1 : 0;
                 int loc1 = thickness % 2 == 0 ? midPoint + stkWidth / 2 - stkWidth : midPoint;
                 int loc2 = thickness % 2 == 0 ? midPoint + stkWidth / 2 : midPoint + stkWidth;
                 // scaled corner
-                int corner = (int) Math.round(CORNER * at.getScaleX());
+                int corner = (int) Math.round(CORNER * scaleFactor);
 
                 // Draw the Long highlight lines
                 g.setColor(highlight);
@@ -351,9 +346,9 @@ public void paintBorder(Component c, Graphics g, int x, int y,
             }
 
             // restore previous transform
-            g2d.translate(-xtranslation, -ytranslation);
+            g.translate(-xtranslation, -ytranslation);
             if (resetTransform) {
-                g2d.setColor(oldColor);
+                Graphics2D g2d = (Graphics2D) g;
                 g2d.setTransform(at);
                 g2d.setStroke(oldStk);
             }