[gimp/gimp-2-8] Bug 740634 - Color picker crashes when there are multiple monitors

[Michael Schumacher <schumaml src gnome org>]

commit 33d45047b52c9f51cf0cb7a5c78aa6d7f4b0cd2f
Author: Éric Hoffman <ehoffman videotron ca>
Date:   Sun Apr 30 21:17:46 2017 +0200

    Bug 740634 - Color picker crashes when there are multiple monitors
    
    Use Windows API directly to get a screen pixel, works for all kinds of monitor layouts.

 libgimpwidgets/gimppickbutton.c |   35 +++++++++++++++++++++++++++++++++++
 1 files changed, 35 insertions(+), 0 deletions(-)
---
diff --git a/libgimpwidgets/gimppickbutton.c b/libgimpwidgets/gimppickbutton.c
index 51546eb..a830f32 100644
--- a/libgimpwidgets/gimppickbutton.c
+++ b/libgimpwidgets/gimppickbutton.c
@@ -38,6 +38,11 @@
 #include <ApplicationServices/ApplicationServices.h>
 #endif
 
+#ifdef G_OS_WIN32
+#define WIN32_LEAN_AND_MEAN
+#include <windows.h>
+#endif
+
 /**
  * SECTION: gimppickbutton
  * @title: GimpPickButton
@@ -367,6 +372,34 @@ gimp_pick_button_pick (GdkScreen      *screen,
                        gint            y_root,
                        GimpPickButton *button)
 {
+
+#ifdef G_OS_WIN32
+
+  HDC      hdc;
+  RECT     rect;
+  COLORREF win32_color;
+  GimpRGB  rgb;
+
+  /* For MS Windows, use native GDI functions to get the pixel, as
+   * cairo does not handle the case where you have multiple monitors
+   * with a monitor on the left or above the primary monitor.  That
+   * scenario create a cairo primary surface with negative extent,
+   * which is not handled properly (bug 740634).
+   */
+
+  hdc = GetDC (HWND_DESKTOP);
+  GetClipBox (hdc, &rect);
+  win32_color = GetPixel (hdc, x_root + rect.left, y_root + rect.top);
+  ReleaseDC (HWND_DESKTOP, hdc);
+
+  gimp_rgba_set_uchar (&rgb,
+                       GetRValue (win32_color),
+                       GetGValue (win32_color),
+                       GetBValue (win32_color),
+                       255);
+
+#else
+
 #ifndef GDK_WINDOWING_QUARTZ
 
   GdkWindow       *root_window = gdk_screen_get_root_window (screen);
@@ -414,5 +447,7 @@ gimp_pick_button_pick (GdkScreen      *screen,
 
 #endif /* GDK_WINDOWING_QUARTZ */
 
+#endif /* G_OS_WIN32 */
+
   g_signal_emit (button, pick_button_signals[COLOR_PICKED], 0, &rgb);
 }