From http://www.jwz.org/xscreensaver/xscreensaver-5.36.tar.gz

[xscreensaver] / utils / grabscreen.c

diff --git a/utils/grabscreen.c b/utils/grabscreen.c
index cc5b57522de05d06d31e8cee2811fc4eae033797..77fe3c96bd4c5d5130bc8e337aa6a88e31136b12 100644 (file)
--- a/utils/grabscreen.c
+++ b/utils/grabscreen.c
@@ -1,5 +1,4 @@
-/* xscreensaver, Copyright (c) 1992, 1993, 1994, 1997, 1998, 2003, 2004
- *  Jamie Zawinski <jwz@jwz.org>
+/* xscreensaver, Copyright (c) 1992-2016 Jamie Zawinski <jwz@jwz.org>
  *
  * Permission to use, copy, modify, distribute, and sell this software and its
  * documentation for any purpose is hereby granted without fee, provided that
@@ -15,6 +14,32 @@
    the difference between drawing on the actual root window, and on the fake
    root window used by the screensaver, since at this level the illusion 
    breaks down...
+
+   The hacks themselves use utils/grabclient.c to invoke the
+   "xscreensaver-getimage" program as a sub-process.
+
+   On "real" X11 systems:
+
+       "driver/xscreensaver-getimage" runs the code in this file to grab
+       the X11 root window image as a Pixmap.
+
+   On MacOS systems running X11, which nobody does any more:
+
+       "driver/xscreensaver-getimage" runs the Perl script
+       "driver/xscreensaver-getimage-desktop", which in turn runs the MacOS
+       program "/usr/sbin/screencapture" to get the Mac desktop image as a
+       PNG file.
+
+   On MacOS systems running the native Cocoa build, or on iOS or Android
+   systems:
+
+       "driver/xscreensaver-getimage" is not used.  Instead, each saver's
+       "utils/grabclient.c" links against "OSX/grabclient-osx.m",
+       "OSX/grabclient-ios.m" or "jwxyz/jwxyz-android.c" to grab
+       screenshots directly without invoking a sub-process to do it.
+
+   See the comment at the top of utils/grabclient.c for a more detailed
+   explanation.
  */
 
 #include "utils.h"
@@ -291,12 +316,12 @@ grab_screen_image_internal (Screen *screen, Window window)
       double unmap = 0;
       if (saver_p)
        {
-         unmap = get_float_resource("grabRootDelay", "Seconds");
+         unmap = get_float_resource(dpy, "grabRootDelay", "Seconds");
          if (unmap <= 0.00001 || unmap > 20) unmap = 2.5;
        }
       else
        {
-         unmap = get_float_resource("grabWindowDelay", "Seconds");
+         unmap = get_float_resource(dpy, "grabWindowDelay", "Seconds");
          if (unmap <= 0.00001 || unmap > 20) unmap = 0.66;
        }
       unmap_time = unmap * 100000;
@@ -464,7 +489,7 @@ copy_default_colormap_contents (Screen *screen,
   XQueryColors (dpy, from_cmap, old_colors, max_cells);
 
   got_cells = max_cells;
-  allocate_writable_colors (dpy, to_cmap, pixels, &got_cells);
+  allocate_writable_colors (screen, to_cmap, pixels, &got_cells);
 
   if (grab_verbose_p && got_cells != max_cells)
     fprintf(stderr, "%s: got only %d of %d cells\n", progname,
@@ -717,6 +742,8 @@ read_display (Screen *screen, Window window, Pixmap into_pixmap,
 
 /* Makes and installs a colormap that makes a PseudoColor or DirectColor
    visual behave like a TrueColor visual of the same depth.
+
+   #### Duplicated in driver/xscreensaver-getimage.c
  */
 static void
 allocate_cubic_colormap (Screen *screen, Window window, Visual *visual)
@@ -732,7 +759,7 @@ allocate_cubic_colormap (Screen *screen, Window window, Visual *visual)
 
   XGetWindowAttributes (dpy, window, &xgwa);
   cmap = xgwa.colormap;
-  depth = visual_depth(screen, visual);
+  depth = visual_depth (screen, visual);
 
   switch (depth)
     {
@@ -784,6 +811,11 @@ allocate_cubic_colormap (Screen *screen, Window window, Visual *visual)
   }
 }
 
+/* Find the pixel index that is closest to the given color
+   (using linear distance in RGB space -- which is far from the best way.)
+
+   #### Duplicated in driver/xscreensaver-getimage.c
+ */
 static unsigned long
 find_closest_pixel (XColor *colors, int ncolors,
                     unsigned long r, unsigned long g, unsigned long b)
@@ -819,6 +851,13 @@ find_closest_pixel (XColor *colors, int ncolors,
 }
 
 
+/* Given an XImage with 8-bit or 12-bit RGB data, convert it to be 
+   displayable with the given X colormap.  The farther from a perfect
+   color cube the contents of the colormap are, the lossier the 
+   transformation will be.  No dithering is done.
+
+   #### Duplicated in driver/xscreensaver-getimage.c
+ */
 void
 remap_image (Screen *screen, Window window, Colormap cmap, XImage *image)
 {