main: Support overline, SGR 53/55

Similar to the underline, incl. the *-thickness and *-offset options.

config.c

@@ -1078,6 +1078,12 @@ parse_section_main(struct context *ctx)
     else if (streq(key, "strikeout-thickness"))
         return value_to_pt_or_px(ctx, &conf->strikeout_thickness);
 
+    else if (streq(key, "overline-thickness"))
+        return value_to_pt_or_px(ctx, &conf->overline_thickness);
+
+    else if (streq(key, "overline-offset"))
+        return value_to_pt_or_px(ctx, &conf->overline_offset);
+
     else if (streq(key, "dpi-aware"))
         return value_to_bool(ctx, &conf->dpi_aware);
 
@@ -3476,6 +3482,8 @@ config_load(struct config *conf, const char *conf_path,
         .box_drawings_uses_font_glyphs = false,
         .underline_thickness = {.pt = 0., .px = -1},
         .strikeout_thickness = {.pt = 0., .px = -1},
+        .overline_thickness = {.pt = 0., .px = -1},
+        .overline_offset = {.pt = 0., .px = -1},
         .dpi_aware = false,
         .gamma_correct = false,
         .uppercase_regex_insert = true,

config.h

@@ -273,6 +273,9 @@ struct config {
 
     struct pt_or_px strikeout_thickness;
 
+    struct pt_or_px overline_thickness;
+    struct pt_or_px overline_offset;
+
     bool box_drawings_uses_font_glyphs;
     bool can_shape_grapheme;
 

csi.c

@@ -150,6 +150,9 @@ csi_sgr(struct terminal *term)
         case 28: term->vt.attrs.conceal = false; break;
         case 29: term->vt.attrs.strikethrough = false; break;
 
+        case 53: term->vt.attrs.overline = true; break;
+        case 55: term->vt.attrs.overline = false; break;
+
         /* Regular foreground colors */
         case 30:
         case 31:

doc/foot-ctlseqs.7.scd

@@ -175,6 +175,10 @@ m*.
 :  Disable conceal
 |  29
 :  Disable crossed-out
+|  53
+:  Overline
+|  55
+:  Disable overline
 |  30-37
 :  Select foreground color (using *regularN* in *foot.ini*(5))
 |  38

doc/foot.ini.5.scd

@@ -198,6 +198,29 @@ empty string to be set, but it must be quoted: *KEY=""*)
 
 	Default: _unset_
 
+*overline-thickness*
+	Use a custom thickness (height) for overlines. The thickness is, by
+	default, in _points_.
+
+	To specify a thickness in _pixels_, append *px*:
+	*overline-thickness=1px*.
+
+	If left unset (the default), the font's underline thickness is used.
+
+	Default: _unset_
+
+*overline-offset*
+	Vertical offset of the overline from the top of the cell. The offset is,
+	by default, in _points_.
+
+	To specify an offset in _pixels_, append *px*:
+	*overline-offset=2px*.
+
+	If left unset (the default), the overline is drawn at the absolute top
+	of the cell (offset = 0).
+
+	Default: _unset_ (0)
+
 *gamma-correct-blending*
 	Boolean. When enabled, foot will do gamma-correct blending in
 	linear color space. This is how font glyphs are supposed to be

render.c

@@ -598,6 +598,27 @@ draw_strikeout(const struct terminal *term, pixman_image_t *pix,
             cols * term->cell_width, thickness});
 }
 
+static void
+draw_overline(const struct terminal *term, pixman_image_t *pix,
+              const struct fcft_font *font,
+              const pixman_color_t *color, int x, int y, int cols)
+{
+    const int thickness = term->conf->overline_thickness.px >= 0
+        ? term_pt_or_px_as_pixels(
+            term, &term->conf->overline_thickness)
+        : font->underline.thickness;
+
+    const int offset = term->conf->overline_offset.px >= 0
+        ? term_pt_or_px_as_pixels(
+            term, &term->conf->overline_offset)
+        : 0;
+
+    pixman_image_fill_rectangles(
+        PIXMAN_OP_SRC, pix, color,
+        1, &(pixman_rectangle16_t){
+            x, y + offset, cols * term->cell_width, thickness});
+}
+
 static void
 cursor_colors_for_cell(const struct terminal *term, const struct cell *cell,
                        const pixman_color_t *fg, const pixman_color_t *bg,
@@ -1173,6 +1194,9 @@ render_cell(struct terminal *term, pixman_image_t *pix,
     if (cell->attrs.strikethrough)
         draw_strikeout(term, pix, font, &fg, x, y, cell_cols);
 
+    if (cell->attrs.overline)
+        draw_overline(term, pix, font, &fg, x, y, cell_cols);
+
     if (unlikely(cell->attrs.url)) {
         pixman_color_t url_color = color_hex_to_pixman(
             term->conf->colors_dark.use_custom.url

terminal.h

@@ -57,8 +57,11 @@ struct attributes {
     bool selected:1;
     bool url:1;
     uint32_t bg:24;
+
+    bool overline:1;
+    uint32_t reserved:31;  /* Future attributes? */
 };
-static_assert(sizeof(struct attributes) == 8, "VT attribute struct too large");
+static_assert(sizeof(struct attributes) == 12, "VT attribute struct size mismatch");
 
 /* Last valid Unicode code point is 0x0010FFFFul */
 #define CELL_COMB_CHARS_LO          0x00200000ul
@@ -69,7 +72,7 @@ struct cell {
     char32_t wc;
     struct attributes attrs;
 };
-static_assert(sizeof(struct cell) == 12, "bad size");
+static_assert(sizeof(struct cell) == 16, "bad size");
 
 struct scroll_region {
     int start;