Correctly premultiply background color of fringe bitmaps

* src/xterm.c (x_draw_fringe_bitmap): Premultiply alphas by
alpha_background.

1 files changed, 12 insertions, 2 deletions

diff --git a/src/xterm.c b/src/xterm.c
index bd0fdde01ee..469077c8972 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -2111,6 +2111,7 @@ x_draw_fringe_bitmap (struct window *w, struct glyph_row *row, struct draw_fring
       int depth = FRAME_DISPLAY_INFO (f)->n_planes;
       XGCValues gcv;
       unsigned long background = face->background;
+      XColor bg;
 #ifdef HAVE_XRENDER
       Picture picture = None;
       XRenderPictureAttributes attrs;
@@ -2123,9 +2124,18 @@ x_draw_fringe_bitmap (struct window *w, struct glyph_row *row, struct draw_fring
       else
         bits = (char *) p->bits + p->dh;
 
-      if (FRAME_DISPLAY_INFO (f)->alpha_bits)
+      if (FRAME_DISPLAY_INFO (f)->alpha_bits
+          && f->alpha_background < 1.0)
         {
-          background = (background & ~FRAME_DISPLAY_INFO (f)->alpha_mask);
+          bg.pixel = background;
+          x_query_colors (f, &bg, 1);
+          bg.red *= f->alpha_background;
+          bg.green *= f->alpha_background;
+          bg.blue *= f->alpha_background;
+
+          background = x_make_truecolor_pixel (FRAME_DISPLAY_INFO (f),
+                                               bg.red, bg.green, bg.blue);
+          background &= ~FRAME_DISPLAY_INFO (f)->alpha_mask;
           background |= (((unsigned long) (f->alpha_background * 0xffff)
                           >> (16 - FRAME_DISPLAY_INFO (f)->alpha_bits))
                          << FRAME_DISPLAY_INFO (f)->alpha_offset);