Ensure the row pointer is visible before moving it

If the user has manually scrolled the window by way of the scrollbar,
when they push j/k to move the pointer we should reposition it onto
the current viewport first, so the window stays roughly where the
user has positioned it.

Signed-off-by: Shawn O. Pearce <sop@google.com>

2 files changed, 40 insertions, 0 deletions

diff --git a/src/main/java/com/google/gerrit/client/patches/AbstractPatchContentTable.java b/src/main/java/com/google/gerrit/client/patches/AbstractPatchContentTable.java
index bdce4d22e1..1e051e075e 100644
--- a/src/main/java/com/google/gerrit/client/patches/AbstractPatchContentTable.java
+++ b/src/main/java/com/google/gerrit/client/patches/AbstractPatchContentTable.java
@@ -525,6 +525,7 @@ public abstract class AbstractPatchContentTable extends NavigationTable<Object>
 
     @Override
     public void onKeyPress(final KeyPressEvent event) {
+      ensurePointerVisible();
       for (int row = getCurrentRow(); 0 <= row; row--) {
         final Object item = getRowItem(row);
         if (item instanceof PatchLine) {
@@ -559,6 +560,7 @@ public abstract class AbstractPatchContentTable extends NavigationTable<Object>
 
     @Override
     public void onKeyPress(final KeyPressEvent event) {
+      ensurePointerVisible();
       moveToPrevChunk(getCurrentRow());
     }
   }
@@ -570,6 +572,7 @@ public abstract class AbstractPatchContentTable extends NavigationTable<Object>
 
     @Override
     public void onKeyPress(final KeyPressEvent event) {
+      ensurePointerVisible();
       moveToNextChunk(getCurrentRow());
     }
   }
diff --git a/src/main/java/com/google/gerrit/client/ui/NavigationTable.java b/src/main/java/com/google/gerrit/client/ui/NavigationTable.java
index 343eb331ea..724e1c7e00 100644
--- a/src/main/java/com/google/gerrit/client/ui/NavigationTable.java
+++ b/src/main/java/com/google/gerrit/client/ui/NavigationTable.java
@@ -15,6 +15,7 @@
 package com.google.gerrit.client.ui;
 
 import com.google.gerrit.client.Gerrit;
+import com.google.gwt.dom.client.Document;
 import com.google.gwt.event.dom.client.KeyPressEvent;
 import com.google.gwt.event.shared.HandlerRegistration;
 import com.google.gwt.user.client.DOM;
@@ -88,6 +89,39 @@ public abstract class NavigationTable<RowItem> extends FancyFlexTable<RowItem> {
     return currentRow;
   }
 
+  protected void ensurePointerVisible() {
+    final int max = table.getRowCount();
+    int row = currentRow;
+    final int init = row;
+    if (row < 0) {
+      row = 0;
+    } else if (max <= row) {
+      row = max - 1;
+    }
+
+    final CellFormatter fmt = table.getCellFormatter();
+    final int sTop = Document.get().getScrollTop();
+    final int sEnd = sTop + Document.get().getClientHeight();
+
+    while (0 <= row && row < max) {
+      final Element cur = DOM.getParent(fmt.getElement(row, C_ARROW));
+      final int cTop = cur.getAbsoluteTop();
+      final int cEnd = cTop + cur.getOffsetHeight();
+
+      if (cEnd < sTop) {
+        row++;
+      } else if (sEnd < cTop) {
+        row--;
+      } else if (getRowItem(row) != null) {
+        break;
+      }
+    }
+
+    if (init != row) {
+      movePointerTo(row, false);
+    }
+  }
+
   protected void movePointerTo(final int newRow) {
     movePointerTo(newRow, true);
   }
@@ -186,6 +220,7 @@ public abstract class NavigationTable<RowItem> extends FancyFlexTable<RowItem> {
 
     @Override
     public void onKeyPress(final KeyPressEvent event) {
+      ensurePointerVisible();
       onUp();
     }
   }
@@ -197,6 +232,7 @@ public abstract class NavigationTable<RowItem> extends FancyFlexTable<RowItem> {
 
     @Override
     public void onKeyPress(final KeyPressEvent event) {
+      ensurePointerVisible();
       onDown();
     }
   }
@@ -208,6 +244,7 @@ public abstract class NavigationTable<RowItem> extends FancyFlexTable<RowItem> {
 
     @Override
     public void onKeyPress(final KeyPressEvent event) {
+      ensurePointerVisible();
       onOpen();
     }
   }