Fix Fl_Copy_Surface under Windows 10 when the desktop scaling factor value is > 100 %

git-svn-id: file:///fltk/svn/fltk/branches/branch-1.3-porting@11899 ea41ed52-d2ee-0310-a9c1-e6b18d33e121

src/drivers/GDI/Fl_GDI_Copy_Surface_Driver.cxx

@@ -22,6 +22,7 @@
 #include <FL/Fl_Copy_Surface.H>
 #include <FL/x.H>
 #include "Fl_GDI_Graphics_Driver.H"
+#include "../WinAPI/Fl_WinAPI_Screen_Driver.H"
 #include <windows.h>
 
 class Fl_GDI_Copy_Surface_Driver : public Fl_Copy_Surface_Driver {
@@ -58,8 +59,10 @@ Fl_GDI_Copy_Surface_Driver::Fl_GDI_Copy_Surface_Driver(int w, int h) : Fl_Copy_S
   ReleaseDC(NULL, hdc);
   float factorw = (100.f * hmm) / hdots;
   float factorh = (100.f * vmm) / vdots;
+  // Global display scaling factor: 1, 1.25, 1.5, 1.75, etc...
+  float scaling = Fl_WinAPI_Screen_Driver::desktop_scaling_factor();
   
-  RECT rect; rect.left = 0; rect.top = 0; rect.right = (LONG)(w * factorw); rect.bottom = (LONG)(h * factorh);
+  RECT rect; rect.left = 0; rect.top = 0; rect.right = (LONG)((w/scaling) * factorw); rect.bottom = (LONG)((h/scaling) * factorh);
   gc = CreateEnhMetaFile (NULL, NULL, &rect, NULL);
   if (gc != NULL) {
     SetTextAlign(gc, TA_BASELINE|TA_LEFT);

src/drivers/WinAPI/Fl_WinAPI_Screen_Driver.H

@@ -52,6 +52,7 @@ public:
   virtual int h();
   virtual void screen_xywh(int &X, int &Y, int &W, int &H, int n);
   virtual void screen_dpi(float &h, float &v, int n=0);
+  static float desktop_scaling_factor();
   virtual void screen_work_area(int &X, int &Y, int &W, int &H, int n);
   // --- audible output
   virtual void beep(int type);

src/drivers/WinAPI/Fl_WinAPI_Screen_Driver.cxx

@@ -656,6 +656,30 @@ Fl_WinAPI_Screen_Driver::read_win_rectangle(uchar *p,		// I - Pixel buffer or NU
   return rgb;
 }
 
+/** Returns the current desktop scaling factor (1.75 for example)
+ */
+float Fl_WinAPI_Screen_Driver::desktop_scaling_factor() {
+  // Compute the global desktop scaling factor: 1, 1.25, 1.5, 1.75, etc...
+  // This factor can be set in Windows 10 by
+  // "Change the size of text, apps and other items" in display settings.
+  // We don't cache this value because it can change while the app is running.
+  HDC hdc = GetDC(NULL);
+  int hr = GetDeviceCaps(hdc, HORZRES); // pixels visible to the app
+#ifndef DESKTOPHORZRES
+#define DESKTOPHORZRES 118
+  /* As of 27 august 2016, the DESKTOPHORZRES flag for GetDeviceCaps()
+   has disappeared from Microsoft online doc, but is quoted in numerous coding examples
+   e.g., https://social.msdn.microsoft.com/Forums/en-US/6acc3b21-23a4-4a00-90b4-968a43e1ccc8/capture-screen-with-high-dpi?forum=vbgeneral
+   It is necessary for the computation of the scaling factor at runtime as done here.
+   */
+#endif
+  int dhr = GetDeviceCaps(hdc, DESKTOPHORZRES); // true number of pixels on display
+  ReleaseDC(NULL, hdc);
+  float scaling = dhr/float(hr);
+  scaling = int(scaling * 100 + 0.5)/100.; // round to 2 digits after decimal point
+  return scaling;
+}
+
 //
 // End of "$Id$".
 //

src/drivers/WinAPI/Fl_WinAPI_Window_Driver.cxx

@@ -27,6 +27,7 @@
 #include <FL/Fl_Overlay_Window.H>
 #include <FL/x.H>
 #include "Fl_WinAPI_Window_Driver.H"
+#include "Fl_WinAPI_Screen_Driver.H"
 #include <windows.h>
 
 #if USE_COLORMAP
@@ -82,32 +83,7 @@ RECT // frame of the decorated window in screen coordinates
       const DWORD DWMWA_EXTENDED_FRAME_BOUNDS = 9;
       if ( DwmGetWindowAttribute(fl_xid(win), DWMWA_EXTENDED_FRAME_BOUNDS, &r, sizeof(RECT)) == S_OK ) {
         need_r = 0;
-        // Compute the global display scaling factor: 1, 1.25, 1.5, 1.75, etc...
-        // This factor can be set in Windows 10 by
-        // "Change the size of text, apps and other items" in display settings.
-        HDC hdc = GetDC(NULL);
-        //int hs = GetDeviceCaps(hdc, HORZSIZE);
-        int hr = GetDeviceCaps(hdc, HORZRES); // pixels visible to the app
-        //int px = GetDeviceCaps(hdc, LOGPIXELSX);
-#ifndef DESKTOPHORZRES
-#define DESKTOPHORZRES 118
-        /* As of 27 august 2016, the DESKTOPHORZRES flag for GetDeviceCaps() 
-         has disappeared from Microsoft online doc, but is quoted in numerous coding examples
-         e.g., https://social.msdn.microsoft.com/Forums/en-US/6acc3b21-23a4-4a00-90b4-968a43e1ccc8/capture-screen-with-high-dpi?forum=vbgeneral
-         It is necessary for the computation of the scaling factor at runtime as done here.
-         */
-#endif
-        int dhr = GetDeviceCaps(hdc, DESKTOPHORZRES); // true number of pixels on display
-        //int vs = GetDeviceCaps(hdc, VERTSIZE);
-        //int vr = GetDeviceCaps(hdc, VERTRES);
-        //int py = GetDeviceCaps(hdc, LOGPIXELSY);
-        //int dvr = GetDeviceCaps(hdc, DESKTOPVERTRES);
-        ReleaseDC(NULL, hdc);
-        scaling = dhr/float(hr);
-        scaling = int(scaling * 100 + 0.5)/100.; // round to 2 digits after decimal point
-        //fprintf(LOG,
-        //        "HORZSIZE=%d %d, HORZRES=%d %d, LOGPIXELSX=%d %d, DESKTOPHORZRES=%d %d scaling=%f bx=%d bt=%d ",
-        //        hs,vs,hr,vr,px,py,dhr,dvr,scaling);fflush(LOG);
+        scaling = Fl_WinAPI_Screen_Driver::desktop_scaling_factor();
       }
     }
     if (need_r) {