src/generic/textmeasure.cpp

   1 ///////////////////////////////////////////////////////////////////////////////
   2 // Name:        src/generic/textmeasure.cpp
   3 // Purpose:
   4 // Author:      Vadim Zeitlin
   5 // Created:     2012-10-17
   6 // RCS-ID:      $Id$
   7 // Copyright:   (c) 2012 Vadim Zeitlin <vadim@wxwidgets.org>
   8 // Licence:     wxWindows licence
   9 ///////////////////////////////////////////////////////////////////////////////
  10
  11 // ============================================================================
  12 // declarations
  13 // ============================================================================
  14
  15 // ----------------------------------------------------------------------------
  16 // headers
  17 // ----------------------------------------------------------------------------
  18
  19 // for compilers that support precompilation, includes "wx.h".
  20 #include "wx/wxprec.h"
  21
  22 #ifdef __BORLANDC__
  23     #pragma hdrstop
  24 #endif
  25
  26 #include "wx/private/textmeasure.h"
  27
  28 #if wxUSE_GENERIC_TEXTMEASURE
  29
  30 // ============================================================================
  31 // wxTextMeasure generic implementation
  32 // ============================================================================
  33
  34 // We assume that the ports not providing platform-specific wxTextMeasure
  35 // implementation implement the corresponding functions in their wxDC and
  36 // wxWindow classes, so forward back to them instead of using wxTextMeasure
  37 // from there, as usual.
  38 void wxTextMeasure::DoGetTextExtent(const wxString& string,
  39                                     wxCoord *width,
  40                                     wxCoord *height,
  41                                     wxCoord *descent,
  42                                     wxCoord *externalLeading)
  43 {
  44     if ( m_dc )
  45     {
  46         m_dc->GetTextExtent(string, width, height,
  47                             descent, externalLeading, m_font);
  48     }
  49     else if ( m_win )
  50     {
  51         m_win->GetTextExtent(string, width, height,
  52                              descent, externalLeading, m_font);
  53     }
  54     //else: we already asserted in the ctor, don't do it any more
  55 }
  56
  57 // Each element of the widths array will be the width of the string up to and
  58 // including the corresponding character in text.  This is the generic
  59 // implementation, the port-specific classes should do this with native APIs
  60 // if available and if faster.  Note: pango_layout_index_to_pos is much slower
  61 // than calling GetTextExtent!!
  62
  63 #define FWC_SIZE 256
  64
  65 class FontWidthCache
  66 {
  67 public:
  68     FontWidthCache() : m_scaleX(1), m_widths(NULL) { }
  69     ~FontWidthCache() { delete []m_widths; }
  70
  71     void Reset()
  72     {
  73         if ( !m_widths )
  74             m_widths = new int[FWC_SIZE];
  75
  76         memset(m_widths, 0, sizeof(int)*FWC_SIZE);
  77     }
  78
  79     wxFont m_font;
  80     double m_scaleX;
  81     int *m_widths;
  82 };
  83
  84 static FontWidthCache s_fontWidthCache;
  85
  86 bool wxTextMeasure::DoGetPartialTextExtents(const wxString& text,
  87                                             wxArrayInt& widths,
  88                                             double scaleX)
  89 {
  90     int totalWidth = 0;
  91
  92     // reset the cache if font or horizontal scale have changed
  93     if ( !s_fontWidthCache.m_widths ||
  94          !wxIsSameDouble(s_fontWidthCache.m_scaleX, scaleX) ||
  95          (s_fontWidthCache.m_font != *m_font) )
  96     {
  97         s_fontWidthCache.Reset();
  98         s_fontWidthCache.m_font = *m_font;
  99         s_fontWidthCache.m_scaleX = scaleX;
 100     }
 101
 102     // Calculate the position of each character based on the widths of
 103     // the previous characters. This is inexact for not fixed fonts.
 104     int n = 0;
 105     for ( wxString::const_iterator it = text.begin();
 106           it != text.end();
 107           ++it )
 108     {
 109         const wxChar c = *it;
 110         unsigned int c_int = (unsigned int)c;
 111
 112         int w;
 113         if ((c_int < FWC_SIZE) && (s_fontWidthCache.m_widths[c_int] != 0))
 114         {
 115             w = s_fontWidthCache.m_widths[c_int];
 116         }
 117         else
 118         {
 119             DoGetTextExtent(c, &w, NULL);
 120             if (c_int < FWC_SIZE)
 121                 s_fontWidthCache.m_widths[c_int] = w;
 122         }
 123
 124         totalWidth += w;
 125         widths[n++] = totalWidth;
 126     }
 127
 128     return true;
 129 }
 130
 131 #endif // wxUSE_GENERIC_TEXTMEASURE