[gimp] Issue #5066: Create From Screenshot Crash.

[Jehan <jehanp src gnome org>]

commit 029ffd5778a623940c48d59574acaa0a68fffdaf
Author: nick758 <nick758 yandex ru>
Date:   Sat Jan 2 14:10:51 2021 +0100

    Issue #5066: Create From Screenshot Crash.

 plug-ins/screenshot/screenshot-win32-dwm-api.h |  6 ++++-
 plug-ins/screenshot/screenshot-win32.c         | 31 ++++++++++++++++++++++----
 2 files changed, 32 insertions(+), 5 deletions(-)
---
diff --git a/plug-ins/screenshot/screenshot-win32-dwm-api.h b/plug-ins/screenshot/screenshot-win32-dwm-api.h
index c99513f528..5f5c0f91c0 100644
--- a/plug-ins/screenshot/screenshot-win32-dwm-api.h
+++ b/plug-ins/screenshot/screenshot-win32-dwm-api.h
@@ -43,6 +43,9 @@ typedef enum _DWMWINDOWATTRIBUTE {
   DWMWA_LAST
 } DWMWINDOWATTRIBUTE;
 
+typedef HRESULT (WINAPI* DWMISCOMPOSITIONENABLED) (BOOL *pfEnabled);
+DWMISCOMPOSITIONENABLED DwmIsCompositionEnabled;
+
 static HMODULE dwmApi = NULL;
 
 void
@@ -62,7 +65,8 @@ LoadRequiredDwmFunctions (void)
   if (! dwmApi) return FALSE;
 
   DwmGetWindowAttribute = (DWMGETWINDOWATTRIBUTE) GetProcAddress (dwmApi, "DwmGetWindowAttribute");
-  if (! DwmGetWindowAttribute)
+  DwmIsCompositionEnabled = (DWMISCOMPOSITIONENABLED) GetProcAddress (dwmApi, "DwmIsCompositionEnabled");
+  if (! (DwmGetWindowAttribute && DwmIsCompositionEnabled))
   {
     UnloadRequiredDwmFunctions ();
     return FALSE;
diff --git a/plug-ins/screenshot/screenshot-win32.c b/plug-ins/screenshot/screenshot-win32.c
index 0f0e5edf60..ddf9212c81 100644
--- a/plug-ins/screenshot/screenshot-win32.c
+++ b/plug-ins/screenshot/screenshot-win32.c
@@ -106,6 +106,8 @@ static gboolean doCaptureBitBlt                    (HWND            selectedHwnd
 BOOL CALLBACK dialogProc (HWND, UINT, WPARAM, LPARAM);
 LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM);
 
+gboolean isDwmCompositionEnabled (void);
+
 /* Data structure holding data between runs */
 typedef struct {
   gint root;
@@ -480,7 +482,7 @@ GetAccurateWindowRect_MonitorEnumProc (HMONITOR hMonitor,
   if (! (*rectScreens))
     *rectScreens = (RECT*) g_malloc (sizeof (RECT)*(rectScreensCount+1));
   else
-    *rectScreens = (RECT*) g_realloc (rectScreens,
+    *rectScreens = (RECT*) g_realloc (*rectScreens,
                                       sizeof (RECT)*(rectScreensCount+1));
 
   if (*rectScreens == NULL)
@@ -516,8 +518,8 @@ GetAccurateWindowRect (HWND hwndTarget,
   /* In this case, we did not got the rect from the dwm api so we try to get the rect with the normal 
function */
   if (GetWindowRect (hwndTarget, outRect))
     {
-      /* If the window is maximized then we need and can fix the rect variable 
-       * (we need to do this if the rect isn't coming from dwm api) 
+      /* If the window is maximized then we need and can fix the rect variable
+       * (we need to do this if the rect isn't coming from dwm api)
        */
       ZeroMemory (&windowplacment, sizeof (WINDOWPLACEMENT));
       if (GetWindowPlacement (hwndTarget, &windowplacment) && windowplacment.showCmd == SW_SHOWMAXIMIZED)
@@ -578,6 +580,24 @@ GetAccurateWindowRect (HWND hwndTarget,
   return FALSE;
 }
 
+gboolean isDwmCompositionEnabled (void)
+{
+  HRESULT err;
+  BOOL    result;
+
+  if (LoadRequiredDwmFunctions ())
+    {
+      err = DwmIsCompositionEnabled (&result);
+      if (err != S_OK)
+        {
+          return FALSE;
+        }
+      return result;
+    }
+
+  return FALSE;
+}
+
 /*
  * doCapture
  *
@@ -598,6 +618,8 @@ doCapture (HWND selectedHwnd)
   /* Are we capturing a window or the whole screen */
   if (selectedHwnd)
     {
+      gboolean compositionEnabled;
+
       if (! GetAccurateWindowRect (selectedHwnd, &rect))
       /* For some reason it works only if we return here TRUE. strange... */
           return TRUE;
@@ -605,8 +627,9 @@ doCapture (HWND selectedHwnd)
       /* First try to capture the window with the magnification api.
       *  This will solve the bug https://bugzilla.gnome.org/show_bug.cgi?id=793722/
       */
+      compositionEnabled = isDwmCompositionEnabled ();
 
-      if (! doCaptureMagnificationAPI (selectedHwnd, rect))
+      if (! (compositionEnabled && doCaptureMagnificationAPI (selectedHwnd, rect)))
         {
           /* If for some reason this capture method failed then
           *  capture the window with the normal method: