Fix a case when fl_read_window() did not capture subwindows correctly.

The case was under macOS with a non-GL parent window mapped to a retina display
containing a GL subwindow and if the app did not call Fl::use_high_res_GL(1).

1 files changed, 12 insertions, 10 deletions

diff --git a/src/Fl_Screen_Driver.H b/src/Fl_Screen_Driver.H
index 511f892d2..05924812c 100644
--- a/src/Fl_Screen_Driver.H
+++ b/src/Fl_Screen_Driver.H
@@ -136,16 +136,17 @@ public:
   // we no longer need the on-screen keyboard; it's up to the system to hide it
   virtual void release_keyboard() { }
 
-  // read raw image from a window or an offscreen buffer
-  /* Member function read_win_rectangle() supports the public function
-   fl_read_image() which captures pixel data either from
-   the current window or from an offscreen buffer.
-
-   With fl_read_image() and for capture from a window, the returned pixel array
-   also contains data from any embedded sub-window.
+  /* Member function read_win_rectangle() supports public functions
+   fl_read_image() and fl_capture_window_part() which capture pixel data from
+   a window (or also from an offscreen buffer with fl_read_image).
    
-   In the case of read_win_rectangle() and for capture from a window, only data
-   from the current window is collected.
+   If 'may_capture_subwins' is true, an implementation may or may not capture
+   also the content of subwindows embedded in 'win'. If subwindows were captured,
+   *'did_capture_subwins' is returned set to true. If read_win_rectangle()
+   is called with 'may_capture_subwins' set to true, 'did_capture_subwins' should
+   be set before the call to the address of a boolean set to false.
+   The implementation of this virtual function for the macOS platform has the
+   capability of capturing subwindows when asked for.
    
    A platform may also use its read_win_rectangle() implementation to capture
    window decorations (e.g., title bar). In that case, it is called by
@@ -153,7 +154,8 @@ public:
    
    win is the window to capture from, or NULL to capture from the current offscreen
    */
-  virtual Fl_RGB_Image *read_win_rectangle(int X, int Y, int w, int h, Fl_Window *win) {return NULL;}
+  virtual Fl_RGB_Image *read_win_rectangle(int X, int Y, int w, int h, Fl_Window *win,
+                                           bool may_capture_subwins = false, bool *did_capture_subwins = NULL) {return NULL;}
   static void write_image_inside(Fl_RGB_Image *to, Fl_RGB_Image *from, int to_x, int to_y);
   static Fl_RGB_Image *traverse_to_gl_subwindows(Fl_Group *g, int x, int y, int w, int h,
                                                  Fl_RGB_Image *full_img);