(#136) Limit calls to SetThreadDpiAwarenessContext to Windows 10 clients (#137)

Author: s1hofmann

src/win32/screengrab.c

@@ -1,25 +1,32 @@
 #include "../screengrab.h"
 #include "../endian.h"
 #include <stdlib.h> /* malloc() */
+#include <VersionHelpers.h>
 
 MMRect getScaledRect(MMRect input)
 {
-	// Configure DPI awareness to fetch unscaled display size
-	DPI_AWARENESS_CONTEXT initialDpiAwareness = SetThreadDpiAwarenessContext(DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE_V2);
 	size_t scaledDesktopWidth = (size_t)GetSystemMetrics(SM_CXSCREEN);
 	size_t scaledDesktopHeight = (size_t)GetSystemMetrics(SM_CYSCREEN);
-	// Reset DPI awareness to avoid inconsistencies on future calls to copyMMBitmapFromDisplayInRect
-	SetThreadDpiAwarenessContext(initialDpiAwareness);
+	// Configure DPI awareness to fetch unscaled display size
+	if (IsWindows10OrGreater() && !IsWindowsServer()) {
+		// Re-query desktop dimensions after setting the DPI awareness context
+		// Only to this on Windows 10 client platforms, since earlier versions of Windows and Windows Server do not support this call
+		DPI_AWARENESS_CONTEXT initialDpiAwareness = SetThreadDpiAwarenessContext(DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE_V2);
+		scaledDesktopWidth = (size_t)GetSystemMetrics(SM_CXSCREEN);
+		scaledDesktopHeight = (size_t)GetSystemMetrics(SM_CYSCREEN);
+		// Reset DPI awareness to avoid inconsistencies on future calls to copyMMBitmapFromDisplayInRect
+		SetThreadDpiAwarenessContext(initialDpiAwareness);
+	}
 	size_t desktopWidth = (size_t)GetSystemMetrics(SM_CXSCREEN);
 	size_t desktopHeight = (size_t)GetSystemMetrics(SM_CYSCREEN);
 
 	double scaleX = (double)(desktopWidth / (double)scaledDesktopWidth);
 	double scaleY = (double)(desktopHeight / (double)scaledDesktopHeight);
 
 	return MMRectMake(
-		input.origin.x / scaleX, 
-		input.origin.y / scaleY, 
-		input.size.width / scaleX, 
+		input.origin.x / scaleX,
+		input.origin.y / scaleY,
+		input.size.width / scaleX,
 		input.size.height / scaleY
 	);
 }