Merge branch 'allow-bleeding-glyphs'

CHANGELOG.md

@@ -33,6 +33,9 @@
 
 * `locked-title=no|yes` to `foot.ini`
   (https://codeberg.org/dnkl/foot/issues/386).
+* `tweak.overflowing-glyphs` option, which can be enabled to fix rendering
+  issues with glyphs of any width that appear cut-off
+  (https://codeberg.org/dnkl/foot/issues/592).
 
 
 ### Changed
@@ -45,6 +48,12 @@
 
 ### Deprecated
 ### Removed
+
+* The `tweak.allow-overflowing-double-width-glyphs` and
+  `tweak.pua-double-width` options (which have been superseded by
+  `tweak.overflowing-glyphs`).
+
+
 ### Fixed
 
 * Glyph offset not being taken into account when applying
@@ -69,6 +78,8 @@
 ### Security
 ### Contributors
 
+* [clktmr](https://codeberg.org/clktmr)
+
 
 ## 1.8.1
 

config.c

@@ -2213,16 +2213,10 @@ parse_section_tweak(
         return false;
     }
 
-    else if (strcmp(key, "allow-overflowing-double-width-glyphs") == 0) {
+    else if (strcmp(key, "overflowing-glyphs") == 0) {
-        conf->tweak.allow_overflowing_double_width_glyphs = str_to_bool(value);
+        conf->tweak.overflowing_glyphs = str_to_bool(value);
-        if (!conf->tweak.allow_overflowing_double_width_glyphs)
+        if (!conf->tweak.overflowing_glyphs)
-            LOG_WARN("tweak: disabled overflowing double-width glyphs");
+            LOG_WARN("tweak: disabled overflowing glyphs");
-    }
-
-    else if (strcmp(key, "pua-double-width") == 0) {
-        conf->tweak.pua_double_width = str_to_bool(value);
-        if (conf->tweak.pua_double_width)
-            LOG_WARN("tweak: PUA double width glyphs enabled");
     }
 
     else if (strcmp(key, "damage-whole-window") == 0) {
@@ -2833,7 +2827,7 @@ config_load(struct config *conf, const char *conf_path,
 
         .tweak = {
             .fcft_filter = FCFT_SCALING_FILTER_LANCZOS3,
-            .allow_overflowing_double_width_glyphs = true,
+            .overflowing_glyphs = true,
             .grapheme_shaping = false,
             .grapheme_width_method = GRAPHEME_WIDTH_DOUBLE,
             .delayed_render_lower_ns = 500000,         /* 0.5ms */
@@ -2844,7 +2838,6 @@ config_load(struct config *conf, const char *conf_path,
             .damage_whole_window = false,
             .box_drawing_base_thickness = 0.04,
             .box_drawing_solid_shades = true,
-            .pua_double_width = false,
         },
 
         .notifications = tll_init(),

config.h

@@ -245,7 +245,7 @@ struct config {
 
     struct {
         enum fcft_scaling_filter fcft_filter;
-        bool allow_overflowing_double_width_glyphs;
+        bool overflowing_glyphs;
         bool grapheme_shaping;
         enum {GRAPHEME_WIDTH_WCSWIDTH, GRAPHEME_WIDTH_DOUBLE} grapheme_width_method;
         bool render_timer_osd;
@@ -256,7 +256,6 @@ struct config {
         off_t max_shm_pool_size;
         float box_drawing_base_thickness;
         bool box_drawing_solid_shades;
-        bool pua_double_width;
     } tweak;
 
     user_notifications_t notifications;

doc/foot.ini.5.scd

@@ -847,34 +847,24 @@ any of these options.
 	
 	Default: _lanczos3_.
 
-*allow-overflowing-double-width-glyphs*
+*overflowing-glyphs*
-	Boolean. When enabled, double width glyphs with a character width
+	Boolean. When enabled, glyphs wider than their cell(s) are allowed
-	of 1 are allowed to overflow into the neighbouring cell.
+	to render into one additional neighbouring cell.
 	
-	One use case for this is fonts "icon" characters in the Unicode
+	One use case for this are fonts with wide italic characters that
-	private usage area, e.g. Nerd Fonts, or Powerline Fonts. Without
+	"bend" into the next cell. Without this option, such glyphs will
-	this option, such glyphs will appear "cut off".
+	appear "cut off".
 	
-	Another use case are legacy emoji characters like *WHITE FROWNING
+	Another use case are fonts with "icon" characters in the Unicode
-	FACE*.
+	private usage area, e.g. Nerd Fonts, or Powerline Fonts and legacy
+	emoji characters like *WHITE FROWNING FACE*.
 	
-	Note: this feature uses _heuristics_ to determine *which* glyphs
+	Note: might impact performance depending on the font used.
-	should be allowed to overflow.
+	Especially small font sizes can cause many overflowing glyphs
-	
+	because of subpixel rendering.
-	See also: *pua-double-width*
 	
 	Default: _yes_.
 
-*pua-double-width*
-	Boolean. When enabled, Unicode code points from the private usage
-	area (PUA) are always considered to be double width, regardless of
-	the actual glyph width.
-	
-	Ignored if *allow-overflowing-double-width-glyphs* has been
-	disabled.
-	
-	Default: _no_.
-
 *render-timer*
 	Enables a frame rendering timer, that prints the time it takes to
 	render each frame, in microseconds, either on-screen, to stderr,

render.c

@@ -437,6 +437,20 @@ draw_cursor(const struct terminal *term, const struct cell *cell,
     }
 }
 
+static inline void
+render_cell_prepass(struct terminal *term, struct row *row, int col)
+{
+    for (; col < term->cols - 1; col++) {
+        if (row->cells[col].attrs.confined ||
+            (row->cells[col].attrs.clean == row->cells[col + 1].attrs.clean)) {
+            break;
+        }
+
+        row->cells[col].attrs.clean = 0;
+        row->cells[col + 1].attrs.clean = 0;
+    }
+}
+
 static int
 render_cell(struct terminal *term, pixman_image_t *pix,
             struct row *row, int col, int row_no, bool has_cursor)
@@ -446,6 +460,7 @@ render_cell(struct terminal *term, pixman_image_t *pix,
         return 0;
 
     cell->attrs.clean = 1;
+    cell->attrs.confined = true;
 
     int width = term->cell_width;
     int height = term->cell_height;
@@ -597,51 +612,32 @@ render_cell(struct terminal *term, pixman_image_t *pix,
     cell_cols = max(1, min(cell_cols, cols_left));
 
     /*
-     * Hack!
+     * Determine cells that will bleed into their right neighbor and remember
-     *
+     * them for cleanup in the next frame.
-     * Deal with double-width glyphs for which wcwidth() returns
-     * 1. Typically Unicode private usage area characters,
-     * e.g. powerline, or nerd hack fonts.
-     *
-     * Users can enable a tweak option that lets this glyphs
-     * overflow/bleed into the neighbouring cell.
-     *
-     * We only apply this workaround if:
-     *  - the user has explicitly enabled this feature
-     *  - the *character* width is 1
-     *  - the *glyph* width is at least 1.5 cells
-     *  - the *glyph* width is less than 3 cells
-     *  - *this* column isn’t the last column
-     *  - *this* cells is followed by an empty cell, or a space
      */
-    if (term->conf->tweak.allow_overflowing_double_width_glyphs &&
+    int render_width = cell_cols * width;
-        glyph_count > 0 &&
+    if (term->conf->tweak.overflowing_glyphs &&
-        cell_cols == 1 &&
+        glyph_count > 0)
-        col < term->cols - 1 &&
-        ((glyphs[0]->x + glyphs[0]->width >= term->cell_width * 15 / 10 &&
-          glyphs[0]->x + glyphs[0]->width < 3 * term->cell_width) ||
-         (term->conf->tweak.pua_double_width &&
-          ((base >= 0x00e000 && base <= 0x00f8ff) ||
-           (base >= 0x0f0000 && base <= 0x0ffffd) ||
-           (base >= 0x100000 && base <= 0x10fffd)))) &&
-        (row->cells[col + 1].wc == 0 || row->cells[col + 1].wc == L' '))
     {
-        cell_cols = 2;
+        int glyph_width = 0, advance = 0;
+        for (size_t i = 0; i < glyph_count; i++) {
+            glyph_width = max(glyph_width,
+                              advance + glyphs[i]->x + glyphs[i]->width);
+            advance += glyphs[i]->advance.x;
+        }
 
-        /*
+        if (glyph_width > render_width) {
-         * Ensure the cell we’re overflowing into gets re-rendered, to
+            render_width = min(glyph_width, render_width + width);
-         * ensure it is erased if *this* cell is erased. Note that we
+
-         * do *not* mark the row as dirty - we don’t need to re-render
+            for (int i = 0; i < cell_cols; i++)
-         * the cell if nothing else on the row has changed.
+                row->cells[col + i].attrs.confined = false;
-         */
+        }
-        row->cells[col].attrs.clean = 0;
-        row->cells[col + 1].attrs.clean = 0;
     }
 
     pixman_region32_t clip;
     pixman_region32_init_rect(
         &clip, x, y,
-        cell_cols * term->cell_width, term->cell_height);
+        render_width, term->cell_height);
     pixman_image_set_clip_region32(pix, &clip);
 
     /* Background */
@@ -771,6 +767,10 @@ static void
 render_row(struct terminal *term, pixman_image_t *pix, struct row *row,
            int row_no, int cursor_col)
 {
+    if (term->conf->tweak.overflowing_glyphs)
+        for (int col = term->cols - 1; col >= 0; col--)
+            render_cell_prepass(term, row, col);
+
     for (int col = term->cols - 1; col >= 0; col--)
         render_cell(term, pix, row, col, row_no, cursor_col == col);
 }
@@ -1192,8 +1192,10 @@ render_sixel(struct terminal *term, pixman_image_t *pix,
                         (last_col_needs_erase && last_col))
                     {
                         render_cell(term, pix, row, col, term_row_no, cursor_col == col);
-                    } else
+                    } else {
                         cell->attrs.clean = 1;
+                        cell->attrs.confined = 1;
+                    }
                 }
             }
         }

terminal.h

@@ -42,11 +42,12 @@ struct attributes {
     uint32_t fg:24;
 
     bool clean:1;
+    bool confined:1;
     bool have_fg:1;
     bool have_bg:1;
     uint32_t selected:2;
     bool url:1;
-    uint32_t reserved:2;
+    uint32_t reserved:1;
     uint32_t bg:24;
 };
 static_assert(sizeof(struct attributes) == 8, "VT attribute struct too large");