Fixed positioning of tooltips in multi monitor setups.

ui/views/corewm/cursor_height_provider_win.cc

Index: ui/views/corewm/cursor_height_provider_win.cc
diff --git a/ui/views/corewm/cursor_height_provider_win.cc b/ui/views/corewm/cursor_height_provider_win.cc
new file mode 100644
index 0000000000000000000000000000000000000000..b48cbdffc1cfb3c2ee2b68f52f432e72a5e2ebb2
--- /dev/null
+++ b/ui/views/corewm/cursor_height_provider_win.cc
@@ -0,0 +1,144 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "ui/views/corewm/cursor_height_provider_win.h"
+
+#include <windows.h>
+#include <map>
+
+#include "base/basictypes.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/win/scoped_hdc.h"
+
+namespace {
+typedef scoped_ptr<uint32> PixelData;

[sky, 2014/05/16 17:13:22]

uint32 is deprecated. Use uint32_t (same comment all through this file).

+typedef std::map<HCURSOR, int> HeightStorage;
+
+const uint32 bits_per_uint32 = 32;

[sky, 2014/05/16 17:13:22]

Why not use sizeof(uint32_t) * 8 when you need this?

[Mateusz Szymański, 2014/05/19 07:43:13]

Because uint32 is obviously 32 bits long and if this ever changes ban the person
who makes the change? :P
I can adjust it, no problem.

+// All bits are 1 for transparent portion of monochromatic mask.
+const uint32 transparent_mask = 0xffffffff;

[sky, 2014/05/16 17:13:22]

Use k for constants, eg kTransparentMask.

+// This is height of default pointer arrow in Windows 7.
+const int default_height = 20;
+
+static HeightStorage* cached_heights = nullptr;

[sky, 2014/05/16 17:13:22]

We're not using c++ 11 yet.

+
+// Extracts the pixel data of provided bitmap
+PixelData GetBitmapData(HBITMAP handle, const BITMAPINFO& info, HDC hdc) {
+  PixelData data(nullptr);
+  // Masks are monochromatic.
+  DCHECK_EQ(info.bmiHeader.biBitCount, 1);
+  if (info.bmiHeader.biBitCount != 1)
+    return data.Pass();
+
+  const size_t number_of_colors = 2;
+
+  const size_t header_and_palette =
+      sizeof(info.bmiHeader) + number_of_colors * sizeof(RGBQUAD);
+  // When getting pixel data palette is appended to memory pointed by
+  // BITMAPINFO passed so allocate additional memory to store additional data.
+  scoped_ptr<BITMAPINFO> header(
+      reinterpret_cast<BITMAPINFO*>(new char[header_and_palette]));
+  if (header == nullptr)

[sky, 2014/05/16 17:13:22]

Don't null check news. If new fails we'll crash.

+    return data.Pass();
+  memcpy(header.get(), &(info.bmiHeader), sizeof(info.bmiHeader));
+
+  data.reset(new uint32[info.bmiHeader.biSizeImage / sizeof(uint32)]);
+  if (data == nullptr)

[sky, 2014/05/16 17:13:22]

Same comment here about checking for null.

+    return data.Pass();
+
+  int result = GetDIBits(hdc,

[sky, 2014/05/16 17:13:22]

Shouldn't you check the return value? Perhaps resetting data if not success?

[Mateusz Szymański, 2014/05/19 07:43:13]

Nicely spotted, I was sure I did.

+                         handle,
+                         0,
+                         info.bmiHeader.biHeight,
+                         data.get(),
+                         header.get(),
+                         DIB_RGB_COLORS);
+
+  return data.Pass();
+}
+
+// Checks if the specifed row is transparent in provided bitmap.
+bool IsRowTransparent(const PixelData& data, const uint32 row_size,

[sky, 2014/05/16 17:13:22]

nit: when you wrap, one param per line.

+                      const uint32 last_byte_mask, const uint32 y) {
+  // Set the padding bits to 1 to make mask matching easier.
+  *(data.get() + (y + 1)* row_size - 1) |= last_byte_mask;
+  for (uint32 i = y * row_size; i < (y + 1) * row_size; ++i) {
+    if (*(data.get() + i) != transparent_mask)
+      return false;
+  }
+  return true;
+}
+
+// Gets the vertical offset between specified cursor's hotpoint and it's bottom.
+//
+// Gets the cursor image data and extract cursor's visible height.
+// Based on that get's what should be the vertical offset between cursor's
+// hot point and the tooltip.
+int CalculateCursorHeight(HCURSOR cursor_handle) {
+  base::win::ScopedGetDC hdc(NULL);
+
+  ICONINFO icon = {0};
+  GetIconInfo(cursor_handle, &icon);
+
+  BITMAPINFO bitmap_info = {0};
+  bitmap_info.bmiHeader.biSize = sizeof(bitmap_info.bmiHeader);
+  if (GetDIBits(hdc, icon.hbmMask, 0, 0, NULL, &bitmap_info, DIB_RGB_COLORS) ==
+      0)
+    return default_height;
+
+  // Rows are padded to full DWORDs. OR with this mask will set them to 1
+  // to simplify matching with |transparent_mask|.
+  uint32 last_byte_mask = ~0;
+  const unsigned char bits_to_shift = sizeof(last_byte_mask) * 8 -
+      (bitmap_info.bmiHeader.biWidth % bits_per_uint32);
+  if (bits_to_shift != bits_per_uint32) {
+    last_byte_mask = (last_byte_mask << bits_to_shift);
+  } else {
+    last_byte_mask = 0;
+  }
+
+  const uint32 row_size =
+      (bitmap_info.bmiHeader.biWidth + bits_per_uint32 - 1) / bits_per_uint32;
+  PixelData data(GetBitmapData(icon.hbmMask, bitmap_info, hdc));
+  if (data == nullptr)

[sky, 2014/05/16 17:13:22]

no null check

[Mateusz Szymański, 2014/05/19 10:38:30]

NULL here is return value indicating internal error.

+    return default_height;
+
+  const int cursor_height = GetSystemMetrics(SM_CYCURSOR);
+  int i = bitmap_info.bmiHeader.biHeight - cursor_height;
+  for (; i < bitmap_info.bmiHeader.biHeight; ++i) {
+    if (!IsRowTransparent(data, row_size, last_byte_mask, i)) {
+      i--;
+      break;
+    }
+  }
+  return bitmap_info.bmiHeader.biHeight - i - icon.yHotspot;
+}
+
+}  // namespace
+
+namespace views {
+namespace corewm {
+
+int GetCursorHeight() {
+  CURSORINFO cursor = {0};
+  cursor.cbSize = sizeof(cursor);
+  GetCursorInfo(&cursor);
+
+  if (cached_heights == nullptr) {

[sky, 2014/05/16 17:13:22]

nit: no {}

+    cached_heights = new HeightStorage;
+  }
+
+  HeightStorage::const_iterator cached_height =
+      cached_heights->find(cursor.hCursor);
+  if (cached_height != cached_heights->end())
+    return cached_height->second;
+
+  const int height = CalculateCursorHeight(cursor.hCursor);
+  (*cached_heights)[cursor.hCursor] = height;
+
+  return height;
+}
+
+}  // namespace corewm
+}  // namespace views