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About x_draw_xwidget_glyph_string

From: YAMAMOTO Mitsuharu
Subject: About x_draw_xwidget_glyph_string
Date: Mon, 25 Jan 2016 11:07:16 +0900
User-agent: Wanderlust/2.14.0 (Africa) SEMI/1.14.6 (Maruoka) FLIM/1.14.8 (Shij┼Ź) APEL/10.6 Emacs/22.3 (sparc-sun-solaris2.8) MULE/5.0 (SAKAKI)

I have a question and a comment about x_draw_xwidget_glyph_string in

1. Question about xwidget initialization.

   559  x_draw_xwidget_glyph_string (struct glyph_string *s)
   560  {
   561    /* This method is called by the redisplay engine and places the
   562       xwidget on screen.  Moving and clipping is done here.  Also view
   563       initialization.  */
   564    struct xwidget *xww = s->xwidget;
   565    struct xwidget_view *xv = xwidget_view_lookup (xww, s->w);
   574    /* Do initialization here in the display loop because there is no
   575       other time to know things like window placement etc.  */
   576    xv = xwidget_init_view (xww, s, x, y);

Line 576 indicates a new xwidget view is created in every
x_draw_xwidget_glyph_string call.  But this makes xwidget-view-list
longer and longer, and looks like a waste of memory, if not a leak.
Also, if it is an intended behavior, then it looks strange to look up
a view at Line 565.

2. Comment on clipping.

   578    /* Calculate clipping, which is used for all manner of onscreen
   579       xwidget views.  Each widget border can get clipped by other emacs
   580       objects so there are four clipping variables.  */
   581    clip_right =
   582      min (xww->width,
   583           WINDOW_RIGHT_EDGE_X (s->w) - x -
   584           WINDOW_RIGHT_SCROLL_BAR_AREA_WIDTH (s->w) -
   585           WINDOW_RIGHT_FRINGE_WIDTH (s->w));
   586    clip_left =
   587      max (0,
   588           WINDOW_LEFT_EDGE_X (s->w) - x +
   589           WINDOW_LEFT_SCROLL_BAR_AREA_WIDTH (s->w) +
   590           WINDOW_LEFT_FRINGE_WIDTH (s->w));
   592    clip_bottom =
   593      min (xww->height,
   594           WINDOW_BOTTOM_EDGE_Y (s->w) - WINDOW_MODE_LINE_HEIGHT (s->w) - 
   595    clip_top = max (0, WINDOW_TOP_EDGE_Y (s->w) - y);

I think the calculation of clipping should use the function window_box
rather than manual calculation with various window macros.  Otherwise,
xwidget views will cover horizontal scroll bars, for example.

                                     YAMAMOTO Mitsuharu

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