config: line-height, letter-spacing: values are in pt by default, but we allow px

If the value is specified without a unit, then the value is assumed to
be in points, subject to DPI scaling.

The value can optionally have a ‘px’ suffix, in which case the value
is treated as a raw pixel count.

box-drawing.c

@@ -2064,13 +2064,23 @@ box_drawing(const struct terminal *term, wchar_t wc)
     };
     draw_glyph(wc, &buf);
 
+    const struct config *conf = term->conf;
+
+    int x_ofs = conf->horizontal_letter_offset.px > 0
+        ? conf->horizontal_letter_offset.px
+        : conf->horizontal_letter_offset.pt * term->font_dpi / 72.;
+    int y_ofs = conf->vertical_letter_offset.px > 0
+        ? conf->vertical_letter_offset.px
+        : conf->vertical_letter_offset.pt * term->font_dpi / 72.;
+
+
     struct fcft_glyph *glyph = xmalloc(sizeof(*glyph));
     *glyph = (struct fcft_glyph){
         .wc = wc,
         .cols = 1,
         .pix = pix,
-        .x = -term->conf->horizontal_letter_offset,
-        .y = term->conf->vertical_letter_offset + term->fonts[0]->ascent,
+        .x = -x_ofs,
+        .y = y_ofs + term->fonts[0]->ascent,
         .width = width,
         .height = height,
         .advance = {

config.c

@@ -360,19 +360,6 @@ str_to_bool(const char *s)
         strtoul(s, NULL, 0) > 0;
 }
 
-static bool
-str_to_long(const char *s, int base, long *res)
-{
-    if (s == NULL)
-        return false;
-
-    errno = 0;
-    char *end = NULL;
-
-    *res = strtol(s, &end, base);
-    return errno == 0 && *end == '\0';
-}
-
 static bool
 str_to_ulong(const char *s, int base, unsigned long *res)
 {
@@ -422,6 +409,40 @@ str_to_color(const char *s, uint32_t *color, bool allow_alpha,
     return true;
 }
 
+static bool
+str_to_pt_or_px(const char *s, union pt_or_px *res, struct config *conf,
+                const char *path, int lineno, const char *section, const char *key)
+{
+    size_t len = s != NULL ? strlen(s) : 0;
+    if (len >= 2 && s[len - 2] == 'p' && s[len - 1] == 'x') {
+        errno = 0;
+        char *end = NULL;
+
+        long value = strtol(s, &end, 10);
+        if (!(errno == 0 && end == s + len - 2)) {
+            LOG_AND_NOTIFY_ERR(
+                "%s:%d: [%s]: %s: "
+                "expected an integer directly followed by 'px', got '%s'",
+                path, lineno, section, key, s);
+            return false;
+        }
+        res->pt = 0;
+        res->px = value;
+    } else {
+        double value;
+        if (!str_to_double(s, &value)) {
+            LOG_AND_NOTIFY_ERR(
+                "%s:%d: [%s]: %s: expected a decimal value, got '%s'",
+                path, lineno, section, key, s);
+            return false;
+        }
+        res->pt = value;
+        res->px = 0;
+    }
+
+    return true;
+}
+
 static bool
 parse_section_main(const char *key, const char *value, struct config *conf,
                    const char *path, unsigned lineno)
@@ -572,47 +593,29 @@ parse_section_main(const char *key, const char *value, struct config *conf,
     }
 
     else if (strcmp(key, "line-height") == 0) {
-        unsigned long height;
-        if (!str_to_ulong(value, 10, &height)) {
-            LOG_AND_NOTIFY_ERR(
-                "%s:%d: [default]: line-height: expected an integer, got '%s'",
-                path, lineno, value);
+        if (!str_to_pt_or_px(value, &conf->line_height,
+                             conf, path, lineno, "default", "line-height"))
             return false;
-        }
-        conf->line_height = height;
     }
 
     else if (strcmp(key, "letter-spacing") == 0) {
-        long spacing;
-        if (!str_to_long(value, 10, &spacing)) {
-            LOG_AND_NOTIFY_ERR(
-                "%s:%d: [default]: letter-spacing: expected an integer, got '%s'",
-                path, lineno, value);
+        if (!str_to_pt_or_px(value, &conf->letter_spacing,
+                             conf, path, lineno, "default", "letter-spacing"))
             return false;
-        }
-        conf->letter_spacing = spacing;
     }
 
     else if (strcmp(key, "horizontal-letter-offset") == 0) {
-        long offset;
-        if (!str_to_long(value, 10, &offset)) {
-            LOG_AND_NOTIFY_ERR(
-                "%s:%d: [default]: horizontal-letter-offset: "
-                "expected an integer, got '%s'", path, lineno, value);
+        if (!str_to_pt_or_px(
+                value, &conf->horizontal_letter_offset,
+                conf, path, lineno, "default", "horizontal-letter-offset"))
             return false;
-        }
-        conf->horizontal_letter_offset = offset;
     }
 
     else if (strcmp(key, "vertical-letter-offset") == 0) {
-        long offset;
-        if (!str_to_long(value, 10, &offset)) {
-            LOG_AND_NOTIFY_ERR(
-                "%s:%d: [default]: horizontal-letter-offset: "
-                "expected an integer, got '%s'", path, lineno, value);
+        if (!str_to_pt_or_px(
+                value, &conf->horizontal_letter_offset,
+                conf, path, lineno, "default", "vertical-letter-offset"))
             return false;
-        }
-        conf->vertical_letter_offset = offset;
     }
 
     else if (strcmp(key, "dpi-aware") == 0) {
@@ -2039,10 +2042,10 @@ config_load(struct config *conf, const char *conf_path,
         .bell_action = BELL_ACTION_NONE,
         .startup_mode = STARTUP_WINDOWED,
         .fonts = {tll_init(), tll_init(), tll_init(), tll_init()},
-        .line_height = -1,
-        .letter_spacing = -1,
-        .horizontal_letter_offset = 0,
-        .vertical_letter_offset = 0,
+        .line_height = { .pt = 0, .px = -1, },
+        .letter_spacing = { .pt = 0, .px = 0, },
+        .horizontal_letter_offset = {.pt = 0, .px = 0, },
+        .vertical_letter_offset = {.pt = 0, .px = 0, },
         .dpi_aware = DPI_AWARE_AUTO, /* DPI-aware when scaling-factor == 1 */
         .scrollback = {
             .lines = 1000,

config.h

@@ -54,6 +54,12 @@ struct config_mouse_binding {
     } pipe;
 };
 
+/* If px == -1, neither px nor pt is valid. If px == 0, pt is valid, else px */
+union pt_or_px {
+    int16_t px;
+    float pt;
+};
+
 struct config {
     char *term;
     char *shell;
@@ -85,12 +91,12 @@ struct config {
     config_font_list_t fonts[4];
 
     /* Custom font metrics (-1 = use real font metrics) */
-    int16_t line_height;
-    int16_t letter_spacing;
+    union pt_or_px line_height;
+    union pt_or_px letter_spacing;
 
     /* Adjusted letter x/y offsets */
-    int16_t horizontal_letter_offset;
-    int16_t vertical_letter_offset;
+    union pt_or_px horizontal_letter_offset;
+    union pt_or_px vertical_letter_offset;
 
     struct {
         int lines;

render.c

@@ -256,7 +256,7 @@ color_dim_for_search(pixman_color_t *color)
 static inline int
 font_baseline(const struct terminal *term)
 {
-    return term->conf->vertical_letter_offset + term->fonts[0]->ascent;
+    return term->font_y_ofs + term->fonts[0]->ascent;
 }
 
 static void
@@ -541,7 +541,7 @@ render_cell(struct terminal *term, pixman_image_t *pix,
     pixman_image_t *clr_pix = pixman_image_create_solid_fill(&fg);
 
     if (glyph != NULL) {
-        const int letter_x_ofs = term->conf->horizontal_letter_offset;
+        const int letter_x_ofs = term->font_x_ofs;
 
         if (unlikely(pixman_image_get_format(glyph->pix) == PIXMAN_a8r8g8b8)) {
             /* Glyph surface is a pre-rendered image (typically a color emoji...) */
@@ -1693,7 +1693,7 @@ render_osd(struct terminal *term,
     struct fcft_font *font = term->fonts[0];
     pixman_color_t fg = color_hex_to_pixman(_fg);
 
-    const int x_ofs = term->conf->horizontal_letter_offset;
+    const int x_ofs = term->font_x_ofs;
 
     for (size_t i = 0; i < wcslen(text); i++) {
         const struct fcft_glyph *glyph = fcft_glyph_rasterize(
@@ -2272,7 +2272,7 @@ render_search_box(struct terminal *term)
 
     struct fcft_font *font = term->fonts[0];
     const int x_left = width - visible_width + margin;
-    const int x_ofs = term->conf->horizontal_letter_offset;
+    const int x_ofs = term->font_x_ofs;
     int x = x_left;
     int y = margin;
     pixman_color_t fg = color_hex_to_pixman(term->colors.table[0]);

terminal.c

@@ -629,15 +629,30 @@ term_set_fonts(struct terminal *term, struct fcft_font *fonts[static 4])
     const int old_cell_width = term->cell_width;
     const int old_cell_height = term->cell_height;
 
-    term->cell_width = (term->fonts[0]->space_advance.x > 0
-                        ? term->fonts[0]->space_advance.x
-                        : term->fonts[0]->max_advance.x)
-        + term->conf->letter_spacing;
+    const struct config *conf = term->conf;
 
-    term->cell_height = term->conf->line_height >= 0
-        ? term->conf->line_height
+    term->cell_width =
+        (term->fonts[0]->space_advance.x > 0
+         ? term->fonts[0]->space_advance.x
+         : term->fonts[0]->max_advance.x)
+        + (conf->letter_spacing.px > 0
+           ? conf->letter_spacing.px
+           : conf->letter_spacing.pt * term->font_dpi / 72.);
+
+    term->cell_height = conf->line_height.px >= 0
+        ? (conf->line_height.px > 0
+           ? conf->line_height.px
+           : conf->line_height.pt * term->font_dpi / 72.)
         : max(term->fonts[0]->height,
               term->fonts[0]->ascent + term->fonts[0]->descent);
+
+    term->font_x_ofs = conf->horizontal_letter_offset.px > 0
+        ? conf->horizontal_letter_offset.px
+        : conf->horizontal_letter_offset.pt * term->font_dpi / 72.;
+    term->font_y_ofs = conf->vertical_letter_offset.px > 0
+        ? conf->vertical_letter_offset.px
+        : conf->vertical_letter_offset.pt * term->font_dpi / 72.;
+
     LOG_INFO("cell width=%d, height=%d", term->cell_width, term->cell_height);
 
     if (term->cell_width < old_cell_width ||

terminal.h

@@ -265,6 +265,8 @@ struct terminal {
     struct config_font *font_sizes[4];
     float font_dpi;
     int font_scale;
+    int16_t font_x_ofs;
+    int16_t font_y_ofs;
     enum fcft_subpixel font_subpixel;
 
     /*