Properly clip overlaid fringe bitmaps

* src/xterm.c (x_draw_fringe_bitmap): Save clip rectangle from
x_clip_to_row, and draw only the intersection between it and the
fringe bitmap, for if the bitmap is overlaid, the clip mask will
override the clip rectangle.
(x_clip_to_row): New argument *RECT_RETURN.  All callers
changed.

1 files changed, 43 insertions, 8 deletions

diff --git a/src/xterm.c b/src/xterm.c
index bd779cb21bf..33e12d48912 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -1167,7 +1167,7 @@ static struct terminal *x_create_terminal (struct x_display_info *);
 static void x_frame_rehighlight (struct x_display_info *);
 
 static void x_clip_to_row (struct window *, struct glyph_row *,
-                           enum glyph_row_area, GC);
+                           enum glyph_row_area, GC, XRectangle *);
 static struct scroll_bar *x_window_to_scroll_bar (Display *, Window, int);
 static struct frame *x_window_to_frame (struct x_display_info *, int);
 static void x_scroll_bar_report_motion (struct frame **, Lisp_Object *,
@@ -7842,9 +7842,10 @@ x_draw_fringe_bitmap (struct window *w, struct glyph_row *row,
   Display *display = FRAME_X_DISPLAY (f);
   GC gc = f->output_data.x->normal_gc;
   struct face *face = p->face;
+  XRectangle clip_rect;
 
   /* Must clip because of partially visible lines.  */
-  x_clip_to_row (w, row, ANY_AREA, gc);
+  x_clip_to_row (w, row, ANY_AREA, gc, &clip_rect);
 
   if (p->bx >= 0 && !p->overlay_p)
     {
@@ -7914,6 +7915,30 @@ x_draw_fringe_bitmap (struct window *w, struct glyph_row *row,
 
       memset (&attrs, 0, sizeof attrs);
 #endif
+      XRectangle image_rect, dest;
+      int window_x, window_y, window_width;
+      int px, py, pwidth, pheight;
+
+      /* Intersect the destination rectangle with that of the row.
+         Setting a clip mask overrides the clip rectangles provided by
+         x_clip_to_row, so clipping must be performed by hand.  */
+
+      image_rect.x = p->x;
+      image_rect.y = p->y;
+      image_rect.width = p->wd;
+      image_rect.height = p->h;
+
+      if (!gui_intersect_rectangles (&clip_rect, &image_rect, &dest))
+        /* The entire destination rectangle falls outside the row.  */
+        goto undo_clip;
+
+      /* Extrapolate the source rectangle from the difference between
+         the destination and image rectangles.  */
+
+      px = dest.x - image_rect.x;
+      py = dest.y - image_rect.y;
+      pwidth = dest.width;
+      pheight = dest.height;
 
       if (p->wd > 8)
         bits = (char *) (p->bits + p->dh);
@@ -7985,15 +8010,16 @@ x_draw_fringe_bitmap (struct window *w, struct glyph_row *row,
           x_xr_apply_ext_clip (f, gc);
           XRenderComposite (display, PictOpSrc, picture,
                             None, FRAME_X_PICTURE (f),
-                            0, 0, 0, 0, p->x, p->y, p->wd, p->h);
+                            px, py, px, py, dest.x, dest.y,
+                            pwidth, pheight);
           x_xr_reset_ext_clip (f);
 
           XRenderFreePicture (display, picture);
         }
       else
 #endif
-        XCopyArea (display, pixmap, drawable, gc, 0, 0,
-                   p->wd, p->h, p->x, p->y);
+        XCopyArea (display, pixmap, drawable, gc, px, py,
+                   pwidth, pheight, dest.x, dest.y);
       XFreePixmap (display, pixmap);
 
       if (p->overlay_p)
@@ -8003,6 +8029,8 @@ x_draw_fringe_bitmap (struct window *w, struct glyph_row *row,
           XFreePixmap (display, clipmask);
         }
     }
+
+  undo_clip:
 #endif  /* not USE_CAIRO */
 
   x_reset_clip_rectangles (f, gc);
@@ -25646,13 +25674,17 @@ XTread_socket (struct terminal *terminal, struct input_event *hold_quit)
 /* Set clipping for output in glyph row ROW.  W is the window in which
    we operate.  GC is the graphics context to set clipping in.
 
+   If RECT_RETURN is non-NULL, return the clip rectangle within
+   *RECT_RETURN.
+
    ROW may be a text row or, e.g., a mode line.  Text rows must be
    clipped to the interior of the window dedicated to text display,
    mode lines must be clipped to the whole window.  */
 
 static void
 x_clip_to_row (struct window *w, struct glyph_row *row,
-               enum glyph_row_area area, GC gc)
+               enum glyph_row_area area, GC gc,
+               XRectangle *rect_return)
 {
   struct frame *f = XFRAME (WINDOW_FRAME (w));
   XRectangle clip_rect;
@@ -25667,6 +25699,9 @@ x_clip_to_row (struct window *w, struct glyph_row *row,
   clip_rect.height = row->visible_height;
 
   x_set_clip_rectangles (f, gc, &clip_rect, 1);
+
+  if (rect_return)
+    *rect_return = clip_rect;
 }
 
 
@@ -25715,7 +25750,7 @@ x_draw_hollow_cursor (struct window *w, struct glyph_row *row)
         wd -= 1;
     }
   /* Set clipping, draw the rectangle, and reset clipping again.  */
-  x_clip_to_row (w, row, TEXT_AREA, gc);
+  x_clip_to_row (w, row, TEXT_AREA, gc, NULL);
   x_draw_rectangle (f, gc, x, y, wd, h - 1);
   x_reset_clip_rectangles (f, gc);
 }
@@ -25785,7 +25820,7 @@ x_draw_bar_cursor (struct window *w, struct glyph_row *row, int width, enum text
           FRAME_DISPLAY_INFO (f)->scratch_cursor_gc = gc;
         }
 
-      x_clip_to_row (w, row, TEXT_AREA, gc);
+      x_clip_to_row (w, row, TEXT_AREA, gc, NULL);
 
       if (kind == BAR_CURSOR)
         {