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      1 // Copyright 2014 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #include "ui/views/corewm/cursor_height_provider_win.h"
      6 
      7 #include <windows.h>
      8 #include <algorithm>
      9 #include <map>
     10 
     11 #include "base/basictypes.h"
     12 #include "base/memory/scoped_ptr.h"
     13 #include "base/win/scoped_hdc.h"
     14 
     15 namespace {
     16 typedef scoped_ptr<uint32_t> PixelData;
     17 typedef std::map<HCURSOR, int> HeightStorage;
     18 
     19 const uint32_t kBitsPeruint32 = sizeof(uint32_t) * 8;
     20 // All bits are 1 for transparent portion of monochromatic mask.
     21 const uint32_t kTransparentMask = 0xffffffff;
     22 // This is height of default pointer arrow in Windows 7.
     23 const int kDefaultHeight = 20;
     24 // Masks are monochromatic.
     25 const size_t kNumberOfColors = 2;
     26 const size_t KHeaderAndPalette =
     27       sizeof(BITMAPINFOHEADER) + kNumberOfColors * sizeof(RGBQUAD);
     28 
     29 static HeightStorage* cached_heights = NULL;
     30 
     31 // Extracts the pixel data of provided bitmap
     32 PixelData GetBitmapData(HBITMAP handle, const BITMAPINFO& info, HDC hdc) {
     33   PixelData data;
     34   // Masks are monochromatic.
     35   DCHECK_EQ(info.bmiHeader.biBitCount, 1);
     36   if (info.bmiHeader.biBitCount != 1)
     37     return data.Pass();
     38 
     39   // When getting pixel data palette is appended to memory pointed by
     40   // BITMAPINFO passed so allocate additional memory to store additional data.
     41   scoped_ptr<BITMAPINFO> header(
     42       reinterpret_cast<BITMAPINFO*>(new char[KHeaderAndPalette]));
     43   memcpy(header.get(), &(info.bmiHeader), sizeof(info.bmiHeader));
     44 
     45   data.reset(new uint32_t[info.bmiHeader.biSizeImage / sizeof(uint32_t)]);
     46 
     47   int result = GetDIBits(hdc,
     48                          handle,
     49                          0,
     50                          info.bmiHeader.biHeight,
     51                          data.get(),
     52                          header.get(),
     53                          DIB_RGB_COLORS);
     54 
     55   if (result == 0)
     56     data.reset();
     57 
     58   return data.Pass();
     59 }
     60 
     61 // Checks if the specifed row is transparent in provided bitmap.
     62 bool IsRowTransparent(const PixelData& data,
     63                       const uint32_t row_size,
     64                       const uint32_t last_byte_mask,
     65                       const uint32_t y) {
     66   // Set the padding bits to 1 to make mask matching easier.
     67   *(data.get() + (y + 1) * row_size - 1) |= last_byte_mask;
     68   for (uint32_t i = y * row_size; i < (y + 1) * row_size; ++i) {
     69     if (*(data.get() + i) != kTransparentMask)
     70       return false;
     71   }
     72   return true;
     73 }
     74 
     75 // Gets the vertical offset between specified cursor's hotpoint and it's bottom.
     76 //
     77 // Gets the cursor image data and extract cursor's visible height.
     78 // Based on that get's what should be the vertical offset between cursor's
     79 // hot point and the tooltip.
     80 int CalculateCursorHeight(HCURSOR cursor_handle) {
     81   base::win::ScopedGetDC hdc(NULL);
     82 
     83   ICONINFO icon = {0};
     84   GetIconInfo(cursor_handle, &icon);
     85 
     86   BITMAPINFO bitmap_info = {0};
     87   bitmap_info.bmiHeader.biSize = sizeof(bitmap_info.bmiHeader);
     88   if (GetDIBits(hdc, icon.hbmMask, 0, 0, NULL, &bitmap_info, DIB_RGB_COLORS) ==
     89       0)
     90     return kDefaultHeight;
     91 
     92   // Rows are padded to full DWORDs. OR with this mask will set them to 1
     93   // to simplify matching with |transparent_mask|.
     94   uint32_t last_byte_mask = 0xFFFFFFFF;
     95   const unsigned char bits_to_shift = sizeof(last_byte_mask) * 8 -
     96       (bitmap_info.bmiHeader.biWidth % kBitsPeruint32);
     97   if (bits_to_shift != kBitsPeruint32)
     98     last_byte_mask = (last_byte_mask << bits_to_shift);
     99   else
    100     last_byte_mask = 0;
    101 
    102   const uint32_t row_size =
    103       (bitmap_info.bmiHeader.biWidth + kBitsPeruint32 - 1) / kBitsPeruint32;
    104   PixelData data(GetBitmapData(icon.hbmMask, bitmap_info, hdc));
    105   if (data == NULL)
    106     return kDefaultHeight;
    107 
    108   const int cursor_height = GetSystemMetrics(SM_CYCURSOR);
    109   // Crash data seems to indicate cursor_height may be bigger than the bitmap.
    110   int i = std::max(0, static_cast<int>(bitmap_info.bmiHeader.biHeight) -
    111                    cursor_height);
    112   for (; i < bitmap_info.bmiHeader.biHeight; ++i) {
    113     if (!IsRowTransparent(data, row_size, last_byte_mask, i)) {
    114       i--;
    115       break;
    116     }
    117   }
    118   return bitmap_info.bmiHeader.biHeight - i - icon.yHotspot;
    119 }
    120 
    121 }  // namespace
    122 
    123 namespace views {
    124 namespace corewm {
    125 
    126 int GetCurrentCursorVisibleHeight() {
    127   CURSORINFO cursor = {0};
    128   cursor.cbSize = sizeof(cursor);
    129   GetCursorInfo(&cursor);
    130 
    131   if (cached_heights == NULL)
    132     cached_heights = new HeightStorage;
    133 
    134   HeightStorage::const_iterator cached_height =
    135       cached_heights->find(cursor.hCursor);
    136   if (cached_height != cached_heights->end())
    137     return cached_height->second;
    138 
    139   const int height = CalculateCursorHeight(cursor.hCursor);
    140   (*cached_heights)[cursor.hCursor] = height;
    141 
    142   return height;
    143 }
    144 
    145 }  // namespace corewm
    146 }  // namespace views
    147