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