Allow disabling SetProcessDPIAware() call

Add Windows-specific wxMSWDisableSettingHighDPIAware() function then can
be called before startup (i.e. wxEntry() call) to disable wxWidgets'
handling of DPI awareness. This is useful for code embedded in non-wx
applications as well as for purely wx application that are not
HiDPI-ready (although the latter has the option of forcing
dpiAware=false in the manifest).

See also https://groups.google.com/d/msg/wx-dev/Z0VpgzCY34U/f1FfPqGDppMJ
and #16116.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_3_0_BRANCH@78406 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/msw/init.h

@@ -30,6 +30,10 @@
     typedef char *wxCmdLineArgType;
 #endif
 
+// Call this function to prevent wxMSW from calling SetProcessDPIAware().
+// Must be called before wxEntry().
+extern WXDLLIMPEXP_CORE void wxMSWDisableSettingHighDPIAware();
+
 // Windows-only overloads of wxEntry() and wxEntryStart() which take the
 // parameters passed to WinMain() instead of those passed to main()
 extern WXDLLIMPEXP_CORE bool

interface/wx/app.h

@@ -1089,7 +1089,11 @@ int wxEntry(int& argc, wxChar** argv);
              }
              @endcode
 
+    @onlyfor{wxmsw}
+
     @header{wx/app.h}
+
+    @see wxMSWDisableSettingHighDPIAware()
 */
 int wxEntry(HINSTANCE hInstance,
             HINSTANCE hPrevInstance = NULL,

interface/wx/init.h

@@ -107,5 +107,22 @@ bool wxInitialize(int argc = 0, wxChar **argv = NULL);
 */
 void wxUninitialize();
 
+/**
+    Prevents wxWidgets from setting HighDPI awareness mode.
+
+    wxEntry calls SetDPIProcessAware() early during initialization on Windows.
+    To prevent this (e.g. because wx is embedded in native code and disabling
+    DPI awareness in the manifest is not an option), call this function
+    *before* wxEntry() is called.
+
+    @onlyfor{wxmsw}
+
+    @header{wx/init.h}
+
+    @since 3.0.3, but only available in 3.0.x, not 3.1+ which doesn't make
+           the SetDPIProcessAware() call anymore.
+*/
+void wxMSWDisableSettingHighDPIAware();
+
 //@}
 

src/msw/main.cpp

@@ -297,8 +297,23 @@ void wxSetProcessDPIAware()
 #endif // wxUSE_DYNLIB_CLASS
 }
 
+// It is sometimes undesirable to force DPI awareness on appplications, e.g.
+// when they are artwork heavy and don't have appropriately scaled bitmaps, or
+// when they are using non-wx, DPI-unaware code. Allow disabling
+// SetProcessDPIAware() call.
+//
+// Further discussion:
+//     http://trac.wxwidgets.org/ticket/16116
+//     https://groups.google.com/d/topic/wx-dev/Z0VpgzCY34U/discussion
+bool gs_allowChangingDPIAwareness = true;
+
 } //anonymous namespace
 
+void wxMSWDisableSettingHighDPIAware()
+{
+    gs_allowChangingDPIAwareness = false;
+}
+
 // ----------------------------------------------------------------------------
 // Windows-specific wxEntry
 // ----------------------------------------------------------------------------
@@ -405,6 +420,8 @@ WXDLLEXPORT int wxEntry(HINSTANCE hInstance,
     // http://msdn.microsoft.com/en-us/library/dd464659%28VS.85%29.aspx).
     // Note that we intentionally do it here and not in wxApp, so that it
     // doesn't happen if wx code is hosted in another app (e.g. a plugin).
+    // It can be disabled by calling wxMSWAllowChangingDPIAwareness().
+    if ( gs_allowChangingDPIAwareness )
         wxSetProcessDPIAware();
 
     if ( !wxMSWEntryCommon(hInstance, nCmdShow) )