Add wxGetDPIofHDC() helper function and use it in wxMSW code

No real changes, just replace several pairs of calls to GetDeviceCaps()
with a single helper function call.

include/wx/msw/private.h

@@ -471,6 +471,13 @@ private:
     wxDECLARE_NO_COPY_CLASS(MemoryHDC);
 };
 
+// Helper function returning the resolution of the given HDC.
+inline wxSize wxGetDPIofHDC(HDC hdc)
+{
+    return wxSize(::GetDeviceCaps(hdc, LOGPIXELSX),
+                  ::GetDeviceCaps(hdc, LOGPIXELSY));
+}
+
 // a class which selects a GDI object into a DC in its ctor and deselects in
 // dtor
 class SelectInHDC

src/msw/dc.cpp

@@ -2648,8 +2648,7 @@ wxSize wxMSWDCImpl::GetPPI() const
 
     if ( !ppi.x || !ppi.y )
     {
-        ppi.x = ::GetDeviceCaps(GetHdc(), LOGPIXELSX);
-        ppi.y = ::GetDeviceCaps(GetHdc(), LOGPIXELSY);
+        ppi = wxGetDPIofHDC(GetHdc());
     }
 
     return ppi;

src/msw/graphics.cpp

@@ -2545,11 +2545,11 @@ wxGDIPlusPrintingContext::wxGDIPlusPrintingContext( wxGraphicsRenderer* renderer
 void wxGDIPlusPrintingContext::GetDPI(wxDouble* dpiX, wxDouble* dpiY) const
 {
     // override to use same scaling as wxWindowsPrintPreview::DetermineScaling
-    ScreenHDC hdc;
+    const wxSize dpi = wxGetDPIofHDC(ScreenHDC());
     if ( dpiX )
-        *dpiX = ::GetDeviceCaps(hdc, LOGPIXELSX);
+        *dpiX = dpi.x;
     if ( dpiY )
-        *dpiY = ::GetDeviceCaps(hdc, LOGPIXELSY);
+        *dpiY = dpi.y;
 }
 
 //-----------------------------------------------------------------------------

src/msw/graphicsd2d.cpp

@@ -5316,13 +5316,11 @@ wxGraphicsFont wxD2DRenderer::CreateFont(
 {
     // Use the same DPI as wxFont will use in SetPixelSize, so these cancel
     // each other out and we are left with the actual pixel size.
-    ScreenHDC hdc;
-    wxRealPoint dpi(::GetDeviceCaps(hdc, LOGPIXELSX),
-                    ::GetDeviceCaps(hdc, LOGPIXELSY));
+    const wxSize dpi = wxGetDPIofHDC(ScreenHDC());
 
     return CreateFontAtDPI(
         wxFontInfo(wxSize(sizeInPixels, sizeInPixels)).AllFlags(flags).FaceName(facename),
-        dpi, col);
+        wxRealPoint(dpi.x, dpi.y), col);
 }
 
 wxGraphicsFont wxD2DRenderer::CreateFontAtDPI(const wxFont& font,

src/msw/ole/activex.cpp

@@ -157,23 +157,13 @@ wxDEFINE_EVENT( wxEVT_ACTIVEX, wxActiveXEvent );
 
 static void PixelsToHimetric(SIZEL &sz)
 {
-    static int logX = 0;
-    static int logY = 0;
-
-    if (logY == 0)
-    {
-        // initaliase
-        HDC dc = GetDC(NULL);
-        logX = GetDeviceCaps(dc, LOGPIXELSX);
-        logY = GetDeviceCaps(dc, LOGPIXELSY);
-        ReleaseDC(NULL, dc);
-    }
+    static const wxSize logSz = wxGetDPIofHDC(ScreenHDC());
 
 #define HIMETRIC_INCH   2540
 #define CONVERT(x, logpixels)   wxMulDivInt32(HIMETRIC_INCH, (x), (logpixels))
 
-    sz.cx = CONVERT(sz.cx, logX);
-    sz.cy = CONVERT(sz.cy, logY);
+    sz.cx = CONVERT(sz.cx, logSz.x);
+    sz.cy = CONVERT(sz.cy, logSz.y);
 
 #undef CONVERT
 #undef HIMETRIC_INCH

src/msw/printwin.cpp

@@ -310,10 +310,8 @@ bool wxWindowsPrintPreview::Print(bool interactive)
 
 void wxWindowsPrintPreview::DetermineScaling()
 {
-    ScreenHDC dc;
-    int logPPIScreenX = ::GetDeviceCaps(dc, LOGPIXELSX);
-    int logPPIScreenY = ::GetDeviceCaps(dc, LOGPIXELSY);
-    m_previewPrintout->SetPPIScreen(logPPIScreenX, logPPIScreenY);
+    const wxSize logPPIScreen = wxGetDPIofHDC(ScreenHDC());
+    m_previewPrintout->SetPPIScreen(logPPIScreen);
 
     // Get a device context for the currently selected printer
     wxPrinterDC printerDC(m_printDialogData.GetPrintData());
@@ -322,8 +320,7 @@ void wxWindowsPrintPreview::DetermineScaling()
     int printerHeightMM;
     int printerXRes;
     int printerYRes;
-    int logPPIPrinterX;
-    int logPPIPrinterY;
+    wxSize logPPIPrinter;
 
     wxRect paperRect;
 
@@ -335,13 +332,12 @@ void wxWindowsPrintPreview::DetermineScaling()
         printerHeightMM = ::GetDeviceCaps(hdc, VERTSIZE);
         printerXRes = ::GetDeviceCaps(hdc, HORZRES);
         printerYRes = ::GetDeviceCaps(hdc, VERTRES);
-        logPPIPrinterX = ::GetDeviceCaps(hdc, LOGPIXELSX);
-        logPPIPrinterY = ::GetDeviceCaps(hdc, LOGPIXELSY);
+        logPPIPrinter = wxGetDPIofHDC(hdc);
 
         paperRect = printerDC.GetPaperRect();
 
-        if ( logPPIPrinterX == 0 ||
-                logPPIPrinterY == 0 ||
+        if ( logPPIPrinter.x == 0 ||
+                logPPIPrinter.y == 0 ||
                     printerWidthMM == 0 ||
                         printerHeightMM == 0 )
         {
@@ -355,8 +351,7 @@ void wxWindowsPrintPreview::DetermineScaling()
         printerHeightMM = 250;
         printerXRes = 1500;
         printerYRes = 2500;
-        logPPIPrinterX = 600;
-        logPPIPrinterY = 600;
+        logPPIPrinter = wxSize(600, 600);
 
         paperRect = wxRect(0, 0, printerXRes, printerYRes);
         m_isOk = false;
@@ -366,11 +361,11 @@ void wxWindowsPrintPreview::DetermineScaling()
     m_previewPrintout->SetPageSizePixels(printerXRes, printerYRes);
     m_previewPrintout->SetPageSizeMM(printerWidthMM, printerHeightMM);
     m_previewPrintout->SetPaperRectPixels(paperRect);
-    m_previewPrintout->SetPPIPrinter(logPPIPrinterX, logPPIPrinterY);
+    m_previewPrintout->SetPPIPrinter(logPPIPrinter);
 
     // At 100%, the page should look about page-size on the screen.
-    m_previewScaleX = float(logPPIScreenX) / logPPIPrinterX;
-    m_previewScaleY = float(logPPIScreenY) / logPPIPrinterY;
+    m_previewScaleX = float(logPPIScreen.x) / logPPIPrinter.x;
+    m_previewScaleY = float(logPPIScreen.y) / logPPIPrinter.y;
 }
 
 #if wxUSE_ENH_METAFILE

src/msw/window.cpp

@@ -4878,9 +4878,7 @@ wxSize wxWindowMSW::GetDPI() const
 
     if ( !dpi.x || !dpi.y )
     {
-        WindowHDC hdc(hwnd);
-        dpi.x = ::GetDeviceCaps(hdc, LOGPIXELSX);
-        dpi.y = ::GetDeviceCaps(hdc, LOGPIXELSY);
+        dpi = wxGetDPIofHDC(WindowHDC(hwnd));
     }
 
     return dpi;