render_line: use cells based on bitmap width

[ci skip]

kitty/fonts.c

@@ -1008,12 +1008,25 @@ render_line(FONTS_DATA_HANDLE fg_, Line *line) {
         CPUCell *cpu_cell = line->cpu_cells + i;
         GPUCell *gpu_cell = line->gpu_cells + i;
         ssize_t cell_font_idx = font_for_cell(fg, cpu_cell, gpu_cell);
+
         if (is_private_use(cpu_cell->ch)
                 && cell_font_idx != BOX_FONT
                 && cell_font_idx != MISSING_FONT) {
+            int cells;
+            if (cell_font_idx > 0) {
+                Font *font = (fg->fonts + cell_font_idx);
+                glyph_index glyph_id = glyph_id_for_codepoint(font->face, cpu_cell->ch);
+
+                int width = get_glyph_width(font->face, glyph_id);
+                cells = ceilf((float)width / fg->cell_width);
+            } else {
+                cells = 1;
+            }
+
             int j = 0;
             while ((line->cpu_cells[i+j+1].ch == ' ' || line->cpu_cells[i+j+1].ch == 0)
                     && j < MAX_NUM_EXTRA_GLYPHS_PUA
+                    && j < cells
                     && i + j + 1 < line->xnum) {
                 j++;
                 // We have a private use char followed by space(s), render it as a multi-cell ligature.

kitty/fonts.h

@@ -17,6 +17,7 @@
 // API that font backends need to implement
 typedef uint16_t glyph_index;
 unsigned int glyph_id_for_codepoint(PyObject *, char_type);
+int get_glyph_width(PyObject *, glyph_index);
 bool is_glyph_empty(PyObject *, glyph_index);
 hb_font_t* harfbuzz_font_for_face(PyObject*);
 bool set_size_for_face(PyObject*, unsigned int, bool, FONTS_DATA_HANDLE);

kitty/freetype.c

@@ -294,6 +294,20 @@ is_glyph_empty(PyObject *s, glyph_index g) {
 #undef M
 }
 
+int
+get_glyph_width(PyObject *s, glyph_index g) {
+    Face *self = (Face*)s;
+    if (!load_glyph(self, g, FT_LOAD_DEFAULT)) { PyErr_Print(); return false; }
+    FT_Bitmap *bitmap = &self->face->glyph->bitmap;
+#define M self->face->glyph->metrics
+#define B self->face->glyph->bitmap
+    /* printf("glyph: %u bitmap.width: %d bitmap.rows: %d horiAdvance: %ld horiBearingX: %ld horiBearingY: %ld vertBearingX: %ld vertBearingY: %ld vertAdvance: %ld width: %ld height: %ld\n", */
+    /*         g, B.width, B.rows, M.horiAdvance, M.horiBearingX, M.horiBearingY, M.vertBearingX, M.vertBearingY, M.vertAdvance, M.width, M.height); */
+    return bitmap->width;
+#undef M
+#undef B
+}
+
 hb_font_t*
 harfbuzz_font_for_face(PyObject *self) { return ((Face*)self)->harfbuzz_font; }