Factor out text measurement from wxDC and wxWindow into wxTextMeasure.

[wxWidgets.git] / src / generic / textmeasure.cpp

diff --git a/src/generic/textmeasure.cpp b/src/generic/textmeasure.cpp
new file mode 100644 (file)
index 0000000..788e1f6
--- /dev/null
+++ b/src/generic/textmeasure.cpp
@@ -0,0 +1,131 @@
+///////////////////////////////////////////////////////////////////////////////
+// Name:        src/generic/textmeasure.cpp
+// Purpose:
+// Author:      Vadim Zeitlin
+// Created:     2012-10-17
+// RCS-ID:      $Id$
+// Copyright:   (c) 2012 Vadim Zeitlin <vadim@wxwidgets.org>
+// Licence:     wxWindows licence
+///////////////////////////////////////////////////////////////////////////////
+
+// ============================================================================
+// declarations
+// ============================================================================
+
+// ----------------------------------------------------------------------------
+// headers
+// ----------------------------------------------------------------------------
+
+// for compilers that support precompilation, includes "wx.h".
+#include "wx/wxprec.h"
+
+#ifdef __BORLANDC__
+    #pragma hdrstop
+#endif
+
+#include "wx/private/textmeasure.h"
+
+#if wxUSE_GENERIC_TEXTMEASURE
+
+// ============================================================================
+// wxTextMeasure generic implementation
+// ============================================================================
+
+// We assume that the ports not providing platform-specific wxTextMeasure
+// implementation implement the corresponding functions in their wxDC and
+// wxWindow classes, so forward back to them instead of using wxTextMeasure
+// from there, as usual.
+void wxTextMeasure::DoGetTextExtent(const wxString& string,
+                                    wxCoord *width,
+                                    wxCoord *height,
+                                    wxCoord *descent,
+                                    wxCoord *externalLeading)
+{
+    if ( m_dc )
+    {
+        m_dc->GetTextExtent(string, width, height,
+                            descent, externalLeading, m_font);
+    }
+    else if ( m_win )
+    {
+        m_win->GetTextExtent(string, width, height,
+                             descent, externalLeading, m_font);
+    }
+    //else: we already asserted in the ctor, don't do it any more
+}
+
+// Each element of the widths array will be the width of the string up to and
+// including the corresponding character in text.  This is the generic
+// implementation, the port-specific classes should do this with native APIs
+// if available and if faster.  Note: pango_layout_index_to_pos is much slower
+// than calling GetTextExtent!!
+
+#define FWC_SIZE 256
+
+class FontWidthCache
+{
+public:
+    FontWidthCache() : m_scaleX(1), m_widths(NULL) { }
+    ~FontWidthCache() { delete []m_widths; }
+
+    void Reset()
+    {
+        if ( !m_widths )
+            m_widths = new int[FWC_SIZE];
+
+        memset(m_widths, 0, sizeof(int)*FWC_SIZE);
+    }
+
+    wxFont m_font;
+    double m_scaleX;
+    int *m_widths;
+};
+
+static FontWidthCache s_fontWidthCache;
+
+bool wxTextMeasure::DoGetPartialTextExtents(const wxString& text,
+                                            wxArrayInt& widths,
+                                            double scaleX)
+{
+    int totalWidth = 0;
+
+    // reset the cache if font or horizontal scale have changed
+    if ( !s_fontWidthCache.m_widths ||
+         !wxIsSameDouble(s_fontWidthCache.m_scaleX, scaleX) ||
+         (s_fontWidthCache.m_font != *m_font) )
+    {
+        s_fontWidthCache.Reset();
+        s_fontWidthCache.m_font = *m_font;
+        s_fontWidthCache.m_scaleX = scaleX;
+    }
+
+    // Calculate the position of each character based on the widths of
+    // the previous characters. This is inexact for not fixed fonts.
+    int n = 0;
+    for ( wxString::const_iterator it = text.begin();
+          it != text.end();
+          ++it )
+    {
+        const wxChar c = *it;
+        unsigned int c_int = (unsigned int)c;
+
+        int w;
+        if ((c_int < FWC_SIZE) && (s_fontWidthCache.m_widths[c_int] != 0))
+        {
+            w = s_fontWidthCache.m_widths[c_int];
+        }
+        else
+        {
+            DoGetTextExtent(c, &w, NULL);
+            if (c_int < FWC_SIZE)
+                s_fontWidthCache.m_widths[c_int] = w;
+        }
+
+        totalWidth += w;
+        widths[n++] = totalWidth;
+    }
+
+    return true;
+}
+
+#endif // wxUSE_GENERIC_TEXTMEASURE