Add test for harfbuzz shaping

kitty/fonts.c

@@ -485,7 +485,7 @@ shape_run(Cell *first_cell, index_type num_cells, Font *font) {
     num_glyphs = MIN(info_length, positions_length);
 #if 0
         // You can also generate this easily using hb-shape --show-flags --show-extents --cluster-level=1 --shapers=ot /path/to/font/file text
-        hb_buffer_serialize_glyphs(harfbuzz_buffer, 0, num_glyphs, (char*)canvas, 4 * cell_width * cell_height, NULL, font->hb_font, HB_BUFFER_SERIALIZE_FORMAT_TEXT, HB_BUFFER_SERIALIZE_FLAG_DEFAULT | HB_BUFFER_SERIALIZE_FLAG_GLYPH_EXTENTS | HB_BUFFER_SERIALIZE_FLAG_GLYPH_FLAGS);
+        hb_buffer_serialize_glyphs(harfbuzz_buffer, 0, num_glyphs, (char*)canvas, CELLS_IN_CANVAS * cell_width * cell_height, NULL, font->hb_font, HB_BUFFER_SERIALIZE_FORMAT_TEXT, HB_BUFFER_SERIALIZE_FLAG_DEFAULT | HB_BUFFER_SERIALIZE_FLAG_GLYPH_EXTENTS | HB_BUFFER_SERIALIZE_FLAG_GLYPH_FLAGS);
         printf("\n%s\n", canvas);
         clear_canvas();
 #endif
@@ -498,6 +498,19 @@ shape_run(Cell *first_cell, index_type num_cells, Font *font) {
     }
 }
 
+static PyObject*
+test_shape(PyObject UNUSED *self, Line *line) {
+    index_type num = 0;
+    while(num < line->xnum && line->cells[num].ch) num++;
+    load_hb_buffer(line->cells, num);
+    Font *font = &medium_font;
+    hb_shape_full(font->hb_font, harfbuzz_buffer, NULL, 0, SHAPERS);
+    unsigned int num_glyphs;
+    hb_buffer_get_glyph_infos(harfbuzz_buffer, &num_glyphs);
+    hb_buffer_serialize_glyphs(harfbuzz_buffer, 0, num_glyphs, (char*)canvas, CELLS_IN_CANVAS * cell_width * cell_height, NULL, font->hb_font, HB_BUFFER_SERIALIZE_FORMAT_JSON, HB_BUFFER_SERIALIZE_FLAG_DEFAULT | HB_BUFFER_SERIALIZE_FLAG_GLYPH_EXTENTS | HB_BUFFER_SERIALIZE_FLAG_GLYPH_FLAGS);
+    return Py_BuildValue("s", canvas);
+}
+
 static inline void 
 render_run(Cell *first_cell, index_type num_cells, Font *font, FontType ft) {
     switch(ft) {
@@ -726,6 +739,7 @@ static PyMethodDef module_methods[] = {
     METHODB(test_sprite_position_for, METH_VARARGS),
     METHODB(concat_cells, METH_VARARGS),
     METHODB(set_send_sprite_to_gpu, METH_O),
+    METHODB(test_shape, METH_O),
     METHODB(current_fonts, METH_NOARGS),
     METHODB(test_render_line, METH_VARARGS),
     METHODB(get_fallback_font, METH_VARARGS),

kitty/fonts/render.py

@@ -12,7 +12,7 @@ from kitty.constants import isosx
 from kitty.fast_data_types import (
     Screen, change_wcwidth, get_fallback_font, send_prerendered_sprites,
     set_font, set_font_size, set_logical_dpi, set_send_sprite_to_gpu,
-    sprite_map_set_limits, test_render_line
+    sprite_map_set_limits, test_render_line, test_shape
 )
 from kitty.fonts.box_drawing import render_box_char, render_missing_glyph
 
@@ -187,6 +187,20 @@ def render_string(text, family='monospace', size=11.0, dpi=96.0):
     return cell_width, cell_height, cells
 
 
+def shape_string(text="abcd", family='monospace', size=11.0, dpi=96.0):
+    import json
+    try:
+        sprites, cell_width, cell_height = setup_for_testing(family, size, dpi)
+        s = Screen(None, 1, len(text)*2)
+        line = s.line(0)
+        s.draw(text)
+        data = test_shape(line)
+        return json.loads('[' + data + ']')
+    finally:
+        set_send_sprite_to_gpu(None)
+    return data
+
+
 def test_render_string(text='Hello, world!', family='monospace', size=144.0, dpi=96.0):
     from tempfile import NamedTemporaryFile
     from kitty.fast_data_types import concat_cells, current_fonts

kitty_tests/fonts.py

@@ -10,7 +10,7 @@ from kitty.fast_data_types import (
     sprite_map_set_limits, test_render_line, test_sprite_position_for, wcwidth
 )
 from kitty.fonts.box_drawing import box_chars
-from kitty.fonts.render import prerender, render_string, set_font_family
+from kitty.fonts.render import prerender, render_string, set_font_family, shape_string
 from kitty.utils import get_logical_dpi
 
 from . import BaseTest
@@ -68,3 +68,8 @@ class Rendering(BaseTest):
         sz = sum(map(lambda x: wcwidth(ord(x)), text))
         cells = render_string(text)[-1]
         self.ae(len(cells), sz)
+
+    def test_shaping(self):
+        self.assertEqual(len(shape_string('abcd')), 4)
+        flags = [x.get('fl', 0) for x in shape_string('e\u0347\u0305')]
+        self.assertEqual(flags, [0, 1, 1])