Fix artifacting on PGTK when bits are copied with an alpha channel

* src/pgtkterm.c (x_draw_stretch_glyph_string): Draw background
respecting `alpha-background'.
(pgtk_copy_bits): Use CAIRO_OPERATOR_SOURCE to draw onto the
destination surface.

1 files changed, 11 insertions, 7 deletions

diff --git a/src/pgtkterm.c b/src/pgtkterm.c
index 9bb611e4c58..c0b76b077ca 100644
--- a/src/pgtkterm.c
+++ b/src/pgtkterm.c
@@ -2381,7 +2381,7 @@ x_draw_stretch_glyph_string (struct glyph_string *s)
           else
             {
               pgtk_fill_rectangle (s->f, color, x, y, w, h,
-                                   false);
+                                   true);
             }
 
           pgtk_end_cr_clip (s->f);
@@ -2966,17 +2966,20 @@ pgtk_draw_window_cursor (struct window *w, struct glyph_row *glyph_row, int x,
 }
 
 static void
-pgtk_copy_bits (struct frame *f, cairo_rectangle_t * src_rect,
-                cairo_rectangle_t * dst_rect)
+pgtk_copy_bits (struct frame *f, cairo_rectangle_t *src_rect,
+                cairo_rectangle_t *dst_rect)
 {
   cairo_t *cr;
+  GdkWindow *window;
   cairo_surface_t *surface;     /* temporary surface */
 
+  window = gtk_widget_get_window (FRAME_GTK_WIDGET (f));
+
   surface =
-    cairo_surface_create_similar (FRAME_CR_SURFACE (f),
-                                  CAIRO_CONTENT_COLOR_ALPHA,
-                                  (int) src_rect->width,
-                                  (int) src_rect->height);
+    gdk_window_create_similar_surface (window, CAIRO_CONTENT_COLOR_ALPHA,
+                                       FRAME_CR_SURFACE_DESIRED_WIDTH (f),
+                                       FRAME_CR_SURFACE_DESIRED_HEIGHT
+                                       (f));
 
   cr = cairo_create (surface);
   cairo_set_source_surface (cr, FRAME_CR_SURFACE (f), -src_rect->x,
@@ -2988,6 +2991,7 @@ pgtk_copy_bits (struct frame *f, cairo_rectangle_t * src_rect,
 
   cr = pgtk_begin_cr_clip (f);
   cairo_set_source_surface (cr, surface, dst_rect->x, dst_rect->y);
+  cairo_set_operator (cr, CAIRO_OPERATOR_SOURCE);
   cairo_rectangle (cr, dst_rect->x, dst_rect->y, dst_rect->width,
                    dst_rect->height);
   cairo_clip (cr);