diff: allow to change proportions in three-side viewer

platform/diff-impl/src/com/intellij/diff/tools/util/ThreeDiffSplitter.java

@@ -17,27 +17,39 @@ package com.intellij.diff.tools.util;
 
 import com.intellij.diff.tools.util.DiffSplitter.Painter;
 import com.intellij.diff.util.Side;
-import com.intellij.util.containers.ContainerUtil;
+import com.intellij.icons.AllIcons;
 import org.jetbrains.annotations.CalledInAwt;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
 import javax.swing.*;
 import java.awt.*;
+import java.awt.event.MouseEvent;
 import java.util.List;
 
 public class ThreeDiffSplitter extends JPanel {
   private static final int DIVIDER_WIDTH = 30;
 
-  @NotNull private final List<Divider> myDividers;
   @NotNull private final List<? extends JComponent> myContents;
+  @NotNull private final Divider myDivider1;
+  @NotNull private final Divider myDivider2;
+
+  private float myProportion1; // first size divided by (first + second + third)
+  private float myProportion2; // third size divided by (first + second + third)
 
   public ThreeDiffSplitter(@NotNull List<? extends JComponent> components) {
-    myDividers = ContainerUtil.list(new Divider(), new Divider());
+    assert components.size() == 3;
     myContents = components;
+    myDivider1 = new Divider(Side.LEFT);
+    myDivider2 = new Divider(Side.RIGHT);
 
-    addAll(myContents);
-    addAll(myDividers);
+    add(myDivider1);
+    add(myDivider2);
+    for (JComponent content : myContents) {
+      add(content);
+    }
+
+    resetProportions();
   }
 
   @CalledInAwt
@@ -56,32 +68,44 @@ public class ThreeDiffSplitter extends JPanel {
 
   @NotNull
   private Divider getDivider(@NotNull Side side) {
-    return myDividers.get(side.getIndex());
+    return side.select(myDivider1, myDivider2);
   }
 
-  private void addAll(@NotNull List<? extends JComponent> components) {
-    for (JComponent component : components) {
-      add(component, -1);
-    }
+  private void resetProportions() {
+    myProportion1 = myProportion2 = 1f / 3;
+  }
+
+  private void setProportion(float proportion, @NotNull Side side) {
+    proportion = Math.min(1f, Math.max(0f, proportion));
+    float otherProportion = side.select(myProportion2, myProportion1);
+    otherProportion = Math.min(otherProportion, 1f - proportion);
+
+    myProportion1 = side.select(proportion, otherProportion);
+    myProportion2 = side.select(otherProportion, proportion);
   }
 
   @Override
   public void doLayout() {
     int width = getWidth();
     int height = getHeight();
-    int panelWidth = (width - DIVIDER_WIDTH * 2) / 3;
+
+    int dividersTotalWidth = DIVIDER_WIDTH * 2;
+    int contentsTotalWidth = Math.max(width - dividersTotalWidth, 0);
+
+    JComponent[] components = new JComponent[]{myContents.get(0), myDivider1, myContents.get(1), myDivider2, myContents.get(2)};
+    int[] contentWidths = new int[5];
+    contentWidths[1] = DIVIDER_WIDTH; // divider1
+    contentWidths[3] = DIVIDER_WIDTH; // divider2
+    contentWidths[0] = (int)(contentsTotalWidth * myProportion1); // content1
+    contentWidths[4] = (int)(contentsTotalWidth * myProportion2); // content3
+    contentWidths[2] = Math.max(contentsTotalWidth - contentWidths[0] - contentWidths[4], 0); // content2
+
     int x = 0;
-    for (int i = 0; i < myContents.size(); i++) {
-      JComponent component = myContents.get(i);
-      component.setBounds(x, 0, panelWidth, height);
+    for (int i = 0; i < 5; i++) {
+      JComponent component = components[i];
+      component.setBounds(x, 0, contentWidths[i], height);
       component.validate();
-      x += panelWidth;
-      if (i < myDividers.size()) {
-        JComponent divider = myDividers.get(i);
-        divider.setBounds(x, 0, DIVIDER_WIDTH, height);
-        divider.validate();
-        x += DIVIDER_WIDTH;
-      }
+      x += contentWidths[i];
     }
   }
 
@@ -109,12 +133,21 @@ public class ThreeDiffSplitter extends JPanel {
     return new Dimension(width, height);
   }
 
-  private static class Divider extends JComponent {
+  private class Divider extends JPanel {
+    @NotNull private final Side mySide;
     @Nullable private Painter myPainter;
 
+    public Divider(@NotNull Side side) {
+      super(new GridBagLayout());
+      mySide = side;
+      enableEvents(MouseEvent.MOUSE_EVENT_MASK | MouseEvent.MOUSE_MOTION_EVENT_MASK);
+      setCursor(Cursor.getPredefinedCursor(Cursor.W_RESIZE_CURSOR));
+      add(new JLabel(AllIcons.General.SplitGlueH), new GridBagConstraints());
+    }
+
     @Override
-    public void paint(Graphics g) {
-      super.paint(g);
+    protected void paintComponent(Graphics g) {
+      super.paintComponent(g);
       if (myPainter != null) myPainter.paint(g, this);
     }
 
@@ -122,5 +155,32 @@ public class ThreeDiffSplitter extends JPanel {
     public void setPainter(@Nullable Painter painter) {
       myPainter = painter;
     }
+
+    @Override
+    protected void processMouseMotionEvent(MouseEvent e) {
+      super.processMouseMotionEvent(e);
+      if (e.getID() == MouseEvent.MOUSE_DRAGGED) {
+        int totalWidth = ThreeDiffSplitter.this.getWidth();
+        if (totalWidth > 0) {
+          Point point = SwingUtilities.convertPoint(this, e.getPoint(), ThreeDiffSplitter.this);
+          float proportion = (float)mySide.select(point.x, totalWidth - point.x) / (float)totalWidth;
+          setProportion(proportion, mySide);
+
+          revalidate();
+          repaint();
+        }
+      }
+    }
+
+    @Override
+    protected void processMouseEvent(MouseEvent e) {
+      super.processMouseEvent(e);
+      if (e.getID() == MouseEvent.MOUSE_CLICKED && e.getClickCount() == 2) {
+        resetProportions();
+
+        revalidate();
+        repaint();
+      }
+    }
   }
 }