Tk Source Code

 *      back to the window.  Platforms, such as macOS, on which the system
 *      provides double-buffered drawing and GPU-based composition operations
 *      can avoid calls to XGetImage and XCopyArea from the core by defining
 *      the compile-time variable TK_NO_DOUBLE_BUFFERING.  Nonetheless, these
 *      two functions are in the stubs table and therefore could be used by
 *      extensions.
 *
 *      The implementation here does not always work correctly when the source
 *      is a window.  The original version of this function relied on
 *      [NSBitmapImageRep initWithFocusedViewRect:view_rect] which was
 *      deprecated by Apple in OSX 10.14 and also required the use of other
 *      deprecated functions such as [NSView lockFocus]. Apple's suggested
 *      replacement is [NSView cacheDisplayInRect: toBitmapImageRep:] and that
 *      is being used here.  However, cacheDisplayInRect works by calling
 *      [NSView drawRect] after setting the current graphics context to be one
 *      which draws to a bitmap.  There are situations in which this can be
 *      used, e.g. when taking a screenshot of a window.  But it cannot be used
 *      as part of a normal display procedure, using the copy-modify-paste
 *      paradigm that is the basis of the explicit double-buffering.  Since the
 *      copy operation will call the same display procedure that is calling
 *      this function via XGetImage or XCopyArea, this would create an infinite
 *      recursion.
 *
 *      An alternative to the copy-modify-paste paradigm is to use GPU-based
 *      graphics composition, clipping to the specified rectangle.  That is
 *      the approach that must be followed by display procedures on macOS.
 *
 * Results:
 *	Returns an NSBitmapRep representing the image of the given rectangle of
 *      the given drawable. This object is retained. The caller is responsible
 *      for releasing it.
 *
 *      NOTE: The x,y coordinates should be relative to a coordinate system
 *      with origin at the top left, as used by XImage and CGImage, not bottom

    int dst_y)
{
    TkMacOSXDrawingContext dc;
    CGImageRef img = NULL;
    CGRect dstRect;

    // XXXX Need to deal with pixmaps!


    NSView *srcView = TkMacOSXGetNSViewForDrawable(src);
    NSView *dstView = TkMacOSXGetNSViewForDrawable(dst);
    CGRect srcBounds = [srcView bounds];
    CGRect dstBounds = [dstView bounds];

    // To avoid distorting the image when it is drawn we must ensure that
    // the source and destination rectangles have the same size.  This is

	return BadDrawable;
    }

    if (!dc.context) {
	TkMacOSXDbgMsg("Invalid destination drawable - no context.");
	return BadDrawable;
    }



    img = CreateCGImageFromDrawableRect(src, 0, src_x, src_y, width, height, &scaleFactor);












    if (img) {
	unsigned int w = (unsigned int) (CGImageGetWidth(img) / scaleFactor);
	unsigned int h = (unsigned int) (CGImageGetHeight(img) / scaleFactor);
	dstRect = CGRectMake(dst_x, dst_y, w, h);
	TkMacOSXDrawCGImage(dst, gc, dc.context, img,
		gc->foreground, gc->background, dstRect);
	CFRelease(img);
    } else {
	TkMacOSXDbgMsg("Failed to construct CGImage.");

    }

    TkMacOSXRestoreDrawingContext(&dc);
    return Success;
}

/*