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 #ifndef WX_PRECOMP
  27     #include "wx/window.h"
  28     #include "wx/dc.h"
  29 #endif //WX_PRECOMP
  30
  31 #include "wx/private/textmeasure.h"
  32
  33 #if wxUSE_GENERIC_TEXTMEASURE
  34
  35 // ============================================================================
  36 // wxTextMeasure generic implementation
  37 // ============================================================================
  38
  39 // We assume that the ports not providing platform-specific wxTextMeasure
  40 // implementation implement the corresponding functions in their wxDC and
  41 // wxWindow classes, so forward back to them instead of using wxTextMeasure
  42 // from there, as usual.
  43 void wxTextMeasure::DoGetTextExtent(const wxString& string,
  44                                     wxCoord *width,
  45                                     wxCoord *height,
  46                                     wxCoord *descent,
  47                                     wxCoord *externalLeading)
  48 {
  49     if ( m_dc )
  50     {
  51         m_dc->GetTextExtent(string, width, height,
  52                             descent, externalLeading, m_font);
  53     }
  54     else if ( m_win )
  55     {
  56         m_win->GetTextExtent(string, width, height,
  57                              descent, externalLeading, m_font);
  58     }
  59     //else: we already asserted in the ctor, don't do it any more
  60 }
  61
  62 // Each element of the widths array will be the width of the string up to and
  63 // including the corresponding character in text.  This is the generic
  64 // implementation, the port-specific classes should do this with native APIs
  65 // if available and if faster.  Note: pango_layout_index_to_pos is much slower
  66 // than calling GetTextExtent!!
  67
  68 #define FWC_SIZE 256
  69
  70 class FontWidthCache
  71 {
  72 public:
  73     FontWidthCache() : m_scaleX(1), m_widths(NULL) { }
  74     ~FontWidthCache() { delete []m_widths; }
  75
  76     void Reset()
  77     {
  78         if ( !m_widths )
  79             m_widths = new int[FWC_SIZE];
  80
  81         memset(m_widths, 0, sizeof(int)*FWC_SIZE);
  82     }
  83
  84     wxFont m_font;
  85     double m_scaleX;
  86     int *m_widths;
  87 };
  88
  89 static FontWidthCache s_fontWidthCache;
  90
  91 bool wxTextMeasure::DoGetPartialTextExtents(const wxString& text,
  92                                             wxArrayInt& widths,
  93                                             double scaleX)
  94 {
  95     int totalWidth = 0;
  96
  97     // reset the cache if font or horizontal scale have changed
  98     if ( !s_fontWidthCache.m_widths ||
  99          !wxIsSameDouble(s_fontWidthCache.m_scaleX, scaleX) ||
 100          (s_fontWidthCache.m_font != *m_font) )
 101     {
 102         s_fontWidthCache.Reset();
 103         s_fontWidthCache.m_font = *m_font;
 104         s_fontWidthCache.m_scaleX = scaleX;
 105     }
 106
 107     // Calculate the position of each character based on the widths of
 108     // the previous characters. This is inexact for not fixed fonts.
 109     int n = 0;
 110     for ( wxString::const_iterator it = text.begin();
 111           it != text.end();
 112           ++it )
 113     {
 114         const wxChar c = *it;
 115         unsigned int c_int = (unsigned int)c;
 116
 117         int w;
 118         if ((c_int < FWC_SIZE) && (s_fontWidthCache.m_widths[c_int] != 0))
 119         {
 120             w = s_fontWidthCache.m_widths[c_int];
 121         }
 122         else
 123         {
 124             DoGetTextExtent(c, &w, NULL);
 125             if (c_int < FWC_SIZE)
 126                 s_fontWidthCache.m_widths[c_int] = w;
 127         }
 128
 129         totalWidth += w;
 130         widths[n++] = totalWidth;
 131     }
 132
 133     return true;
 134 }
 135
 136 #endif // wxUSE_GENERIC_TEXTMEASURE