[Win32] Use PrintWindow() with PW_RENDERFULLCONTENT flag

Resolves #373.

Author: sratz

bundles/org.eclipse.swt/Eclipse SWT PI/win32/org/eclipse/swt/internal/win32/OS.java

@@ -39,6 +39,7 @@ public class OS extends C {
 	/**
 	 * Values taken from https://en.wikipedia.org/wiki/List_of_Microsoft_Windows_versions
 	 */
+	public static final int WIN32_BUILD_WIN8_1 = 9600; // "Windows 8.1"
 	public static final int WIN32_BUILD_WIN10_1607 = 14393; // "Windows 10 August 2016 Update"
 	public static final int WIN32_BUILD_WIN10_1809 = 17763; // "Windows 10 October 2018 Update"
 	public static final int WIN32_BUILD_WIN10_2004 = 19041; // "Windows 10 May 2020 Update"
@@ -1069,6 +1070,7 @@ public class OS extends C {
 	public static final int PLANES = 0xe;
 	public static final int PM_NOREMOVE = 0x0;
 	public static final int PM_NOYIELD = 0x2;
+	public static final int PW_RENDERFULLCONTENT = 0x2; // undocumented ( >= Windows 8.1)
 	public static final int QS_HOTKEY = 0x0080;
 	public static final int QS_KEY = 0x0001;
 	public static final int QS_MOUSEMOVE = 0x0002;

bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/widgets/Control.java

@@ -2219,15 +2219,23 @@ public boolean print (GC gc) {
 	}
 	int flags = OS.RDW_UPDATENOW | OS.RDW_ALLCHILDREN;
 	OS.RedrawWindow (topHandle, null, 0, flags);
-	printWidget (topHandle, hdc, gc);
+	int printWindowFlags = 0;
+	if (OS.WIN32_BUILD >= OS.WIN32_BUILD_WIN8_1) {
+		/*
+		 * Undocumented flag in windows, which also allows the capturing
+		 * of GPU-drawn areas, e.g. an embedded Edge WebView2.
+		 */
+		printWindowFlags |= OS.PW_RENDERFULLCONTENT;
+	}
+	printWidget (topHandle, hdc, gc, printWindowFlags);
 	if (gdipGraphics != 0) {
 		OS.RestoreDC(hdc, state);
 		Gdip.Graphics_ReleaseHDC(gdipGraphics, hdc);
 	}
 	return true;
 }
 
-void printWidget (long hwnd, long hdc, GC gc) {
+void printWidget (long hwnd, long hdc, GC gc, int printWindowFlags) {
 	/*
 	* Bug in Windows.  For some reason, PrintWindow()
 	* returns success but does nothing when it is called
@@ -2311,7 +2319,7 @@ void printWidget (long hwnd, long hdc, GC gc) {
 		if ((bits1 & OS.WS_VISIBLE) == 0) {
 			OS.ShowWindow (hwnd, OS.SW_SHOW);
 		}
-		success = OS.PrintWindow (hwnd, hdc, 0);
+		success = OS.PrintWindow (hwnd, hdc, printWindowFlags);
 		if ((bits1 & OS.WS_VISIBLE) == 0) {
 			OS.ShowWindow (hwnd, OS.SW_HIDE);
 		}

bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/widgets/Group.java

@@ -294,7 +294,7 @@ boolean mnemonicMatch (char key) {
 }
 
 @Override
-void printWidget (long hwnd, long hdc, GC gc) {
+void printWidget (long hwnd, long hdc, GC gc, int printWindowFlags) {
 	/*
 	* Bug in Windows.  For some reason, PrintWindow()
 	* returns success but does nothing when it is called
@@ -307,7 +307,7 @@ void printWidget (long hwnd, long hdc, GC gc) {
 		if ((bits & OS.WS_VISIBLE) == 0) {
 			OS.ShowWindow (hwnd, OS.SW_SHOW);
 		}
-		success = OS.PrintWindow (hwnd, hdc, 0);
+		success = OS.PrintWindow (hwnd, hdc, printWindowFlags);
 		if ((bits & OS.WS_VISIBLE) == 0) {
 			OS.ShowWindow (hwnd, OS.SW_HIDE);
 		}
@@ -334,6 +334,14 @@ void printWidget (long hwnd, long hdc, GC gc) {
 		Control [] children = _getChildren ();
 		Rectangle rect = getBoundsInPixels ();
 		OS.IntersectClipRect (hdc, 0, 0, rect.width, rect.height);
+		// When looping over child windows and printWindowFlags has
+		// PW_RENDERFULLCONTENT set, then the printed content is always
+		// rendered at the top-left of the passed hdc.
+		// clear that flag
+		// This should be not an issue, since with PW_RENDERFULLCONTENT set
+		// the problem above (push button) does not appear to occurr.
+		// To be on the safe side, clear the flag when dealing with children
+		printWindowFlags &= ~OS.PW_RENDERFULLCONTENT;
 		for (int i=children.length - 1; i>=0; --i) {
 			Point location = children [i].getLocationInPixels ();
 			int graphicsMode = OS.GetGraphicsMode(hdc);
@@ -346,7 +354,7 @@ void printWidget (long hwnd, long hdc, GC gc) {
 			long topHandle = children [i].topHandle();
 			int bits = OS.GetWindowLong (topHandle, OS.GWL_STYLE);
 			if ((bits & OS.WS_VISIBLE) != 0) {
-				children [i].printWidget (topHandle, hdc, gc);
+				children [i].printWidget (topHandle, hdc, gc, printWindowFlags);
 			}
 			if (graphicsMode == OS.GM_ADVANCED) {
 				float [] lpXform = {1, 0, 0, 1, -location.x, -location.y};