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/////////////////////////////////////////////////////////////////////////////
// Name: wx/private/window.h
// Purpose: misc wxWindow helpers
// Author: Vaclav Slavik
// Created: 2010-01-21
// Copyright: (c) 2010 Vaclav Slavik
// Licence: wxWindows licence
/////////////////////////////////////////////////////////////////////////////
#ifndef _WX_PRIVATE_WINDOW_H_
#define _WX_PRIVATE_WINDOW_H_
#include "wx/gdicmn.h"
#include "wx/dynlib.h"
namespace wxPrivate
{
// Windows' computes dialog units using average character width over upper-
// and lower-case ASCII alphabet and not using the average character width
// metadata stored in the font; see
// http://support.microsoft.com/default.aspx/kb/145994 for detailed discussion.
//
// This helper function computes font dimensions in the same way. It works with
// either wxDC or wxWindow argument.
template<typename T>
inline wxSize GetAverageASCIILetterSize(const T& of_what)
{
const wxStringCharType *TEXT_TO_MEASURE =
wxS("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz");
wxSize s = of_what.GetTextExtent(TEXT_TO_MEASURE);
s.x = (s.x / 26 + 1) / 2;
return s;
}
namespace
{
inline bool SupportsPerMonitorDPI()
{
static bool s_checkDPI =
#if defined(__WXMSW__) && wxUSE_DYNLIB_CLASS
// Only check the DPI when GetDpiForWindow is available because the old
// method (GetDeviceCaps) is a lot slower (about 1500 times).
// And when GetDpiForWindow is not available (for example older Windows
// versions), per-monitor DPI (V2) is also not available.
wxLoadedDLL("user32.dll").HasSymbol("GetDpiForWindow");
#else
false;
#endif
return s_checkDPI;
}
}
template <typename T>
class DpiDependentValue
{
public:
// Explicit initialization is needed if T is a primitive type.
DpiDependentValue()
: m_value(), m_dpi()
{ }
bool HasChanged(const wxWindowBase* win)
{
if ( win && SupportsPerMonitorDPI() )
{
const wxSize dpi = win->GetDPI();
if ( dpi != m_dpi )
{
m_dpi = dpi;
return true;
}
}
// Ensure that we return true the first time we're called,
// assuming that the value will always be set to a non-default value.
return m_value == T();
}
void SetAtNewDPI(const T& value)
{
m_value = value;
}
T& Get()
{
return m_value;
}
private:
T m_value;
wxSize m_dpi;
};
} // namespace wxPrivate
#endif // _WX_PRIVATE_WINDOW_H_
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