+/* Compute actual fringe widths */
+
+void
+x_compute_fringe_widths (f, redraw)
+ struct frame *f;
+ int redraw;
+{
+ int o_left = f->output_data.x->left_fringe_width;
+ int o_right = f->output_data.x->right_fringe_width;
+ int o_cols = f->output_data.x->fringe_cols;
+
+ Lisp_Object left_fringe = Fassq (Qleft_fringe, f->param_alist);
+ Lisp_Object right_fringe = Fassq (Qright_fringe, f->param_alist);
+ int left_fringe_width, right_fringe_width;
+
+ if (!NILP (left_fringe))
+ left_fringe = Fcdr (left_fringe);
+ if (!NILP (right_fringe))
+ right_fringe = Fcdr (right_fringe);
+
+ left_fringe_width = ((NILP (left_fringe) || !INTEGERP (left_fringe)) ? 8 :
+ XINT (left_fringe));
+ right_fringe_width = ((NILP (right_fringe) || !INTEGERP (right_fringe)) ? 8 :
+ XINT (right_fringe));
+
+ if (left_fringe_width || right_fringe_width)
+ {
+ int left_wid = left_fringe_width >= 0 ? left_fringe_width : -left_fringe_width;
+ int right_wid = right_fringe_width >= 0 ? right_fringe_width : -right_fringe_width;
+ int conf_wid = left_wid + right_wid;
+ int font_wid = FONT_WIDTH (f->output_data.x->font);
+ int cols = (left_wid + right_wid + font_wid-1) / font_wid;
+ int real_wid = cols * font_wid;
+ if (left_wid && right_wid)
+ {
+ if (left_fringe_width < 0)
+ {
+ /* Left fringe width is fixed, adjust right fringe if necessary */
+ f->output_data.x->left_fringe_width = left_wid;
+ f->output_data.x->right_fringe_width = real_wid - left_wid;
+ }
+ else if (right_fringe_width < 0)
+ {
+ /* Right fringe width is fixed, adjust left fringe if necessary */
+ f->output_data.x->left_fringe_width = real_wid - right_wid;
+ f->output_data.x->right_fringe_width = right_wid;
+ }
+ else
+ {
+ /* Adjust both fringes with an equal amount.
+ Note that we are doing integer arithmetic here, so don't
+ lose a pixel if the total width is an odd number. */
+ int fill = real_wid - conf_wid;
+ f->output_data.x->left_fringe_width = left_wid + fill/2;
+ f->output_data.x->right_fringe_width = right_wid + fill - fill/2;
+ }
+ }
+ else if (left_fringe_width)
+ {
+ f->output_data.x->left_fringe_width = real_wid;
+ f->output_data.x->right_fringe_width = 0;
+ }
+ else
+ {
+ f->output_data.x->left_fringe_width = 0;
+ f->output_data.x->right_fringe_width = real_wid;
+ }
+ f->output_data.x->fringe_cols = cols;
+ f->output_data.x->fringes_extra = real_wid;
+ }
+ else
+ {
+ f->output_data.x->left_fringe_width = 0;
+ f->output_data.x->right_fringe_width = 0;
+ f->output_data.x->fringe_cols = 0;
+ f->output_data.x->fringes_extra = 0;
+ }
+
+ if (redraw && FRAME_VISIBLE_P (f))
+ if (o_left != f->output_data.x->left_fringe_width ||
+ o_right != f->output_data.x->right_fringe_width ||
+ o_cols != f->output_data.x->fringe_cols)
+ redraw_frame (f);
+}