Clamp the hotspot on custom cursors to the custom cursor image's dimensions.

Current behavior:
windows chrome - respect the crazy hotspot
linux chrome - crash
mac chrome - fall back to normal cursor
firefox - clamp the hotspot to the custom cursor image bounds.

So this unifies the behavior of all 3 chrome platforms and matches firefox.

BUG=51709
TEST=see bug for reduction

Review URL: http://codereview.chromium.org/3168003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@55669 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 52 insertions, 0 deletions

diff --git a/webkit/glue/webcursor.cc b/webkit/glue/webcursor.cc
index f09372c..8f76ef9 100644
--- a/webkit/glue/webcursor.cc
+++ b/webkit/glue/webcursor.cc
@@ -57,6 +57,7 @@ void WebCursor::InitFromCursorInfo(const WebCursorInfo& cursor_info) {
   hotspot_ = cursor_info.hotSpot;
   if (IsCustom())
     SetCustomData(cursor_info.customImage);
+  ClampHotspot();
 }
 
 void WebCursor::GetCursorInfo(WebCursorInfo* cursor_info) const {
@@ -100,6 +101,7 @@ bool WebCursor::Deserialize(const Pickle* pickle, void** iter) {
   hotspot_.set_y(hotspot_y);
   custom_size_.set_width(size_x);
   custom_size_.set_height(size_y);
+  ClampHotspot();
 
   custom_data_.clear();
   if (data_len > 0) {
@@ -192,3 +194,14 @@ void WebCursor::ImageFromCustomData(WebImage* image) const {
   image->assign(bitmap);
 }
 #endif
+
+void WebCursor::ClampHotspot() {
+  if (!IsCustom())
+    return;
+
+  // Clamp the hotspot to the custom image's dimensions.
+  hotspot_.set_x(std::max(0,
+                          std::min(custom_size_.width() - 1, hotspot_.x())));
+  hotspot_.set_y(std::max(0,
+                          std::min(custom_size_.height() - 1, hotspot_.y())));
+}
diff --git a/webkit/glue/webcursor.h b/webkit/glue/webcursor.h
index 293bd74..35eb001 100644
--- a/webkit/glue/webcursor.h
+++ b/webkit/glue/webcursor.h
@@ -127,6 +127,9 @@ class WebCursor {
   void SetCustomData(const WebKit::WebImage& image);
   void ImageFromCustomData(WebKit::WebImage* image) const;
 
+  // Clamp the hotspot to the custom image's bounds, if this is a custom cursor.
+  void ClampHotspot();
+
   // WebCore::PlatformCursor type.
   int type_;
 
diff --git a/webkit/glue/webcursor_unittest.cc b/webkit/glue/webcursor_unittest.cc
index 5c1ddfe..6e7701d 100644
--- a/webkit/glue/webcursor_unittest.cc
+++ b/webkit/glue/webcursor_unittest.cc
@@ -4,9 +4,12 @@
 
 #include "base/pickle.h"
 #include "testing/gtest/include/gtest/gtest.h"
+#include "third_party/WebKit/WebKit/chromium/public/WebCursorInfo.h"
 #include "webkit/glue/webcursor.h"
 #include "webkit/tools/test_shell/test_shell_test.h"
 
+using WebKit::WebCursorInfo;
+
 TEST(WebCursorTest, CursorSerialization) {
   WebCursor custom_cursor;
   // This is a valid custom cursor.
@@ -80,3 +83,36 @@ TEST(WebCursorTest, CursorSerialization) {
   EXPECT_FALSE(custom_cursor.Deserialize(&neg_custom_pickle, &iter));
 }
 
+TEST(WebCursorTest, ClampHotspot) {
+  WebCursor custom_cursor;
+  // This is a valid custom cursor.
+  Pickle ok_custom_pickle;
+  // Type and hotspots.
+  ok_custom_pickle.WriteInt(WebCursorInfo::TypeCustom);
+  // Hotspot is invalid --- outside the bounds of the image.
+  ok_custom_pickle.WriteInt(5);
+  ok_custom_pickle.WriteInt(5);
+  // X & Y
+  ok_custom_pickle.WriteInt(2);
+  ok_custom_pickle.WriteInt(2);
+  // Data len including enough data for a 2x2 image.
+  ok_custom_pickle.WriteInt(4 * 4);
+  for (size_t i = 0; i < 4; i++)
+    ok_custom_pickle.WriteUInt32(0);
+  // Custom Windows message.
+  ok_custom_pickle.WriteUInt32(0);
+  void* iter = NULL;
+  ASSERT_TRUE(custom_cursor.Deserialize(&ok_custom_pickle, &iter));
+
+  // Convert to WebCursorInfo, make sure the hotspot got clamped.
+  WebCursorInfo info;
+  custom_cursor.GetCursorInfo(&info);
+  EXPECT_EQ(gfx::Point(1, 1), gfx::Point(info.hotSpot));
+
+  // Set hotspot to an invalid point again, pipe back through WebCursor,
+  // and make sure the hotspot got clamped again.
+  info.hotSpot = gfx::Point(-1, -1);
+  custom_cursor.InitFromCursorInfo(info);
+  custom_cursor.GetCursorInfo(&info);
+  EXPECT_EQ(gfx::Point(0, 0), gfx::Point(info.hotSpot));
+}