From 23097ee1846946913516475e926ec6fa4d0e40b8 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Mon, 10 Feb 2025 16:31:03 +0530
Subject: [PATCH] Function to easily test decoration rendering

---
 kitty/fast_data_types.pyi |  1 +
 kitty/fonts.c             | 13 +++++++++++++
 kitty/fonts/render.py     | 10 +++++++++-
 3 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/kitty/fast_data_types.pyi b/kitty/fast_data_types.pyi
index 80d50383e..b22e6bd66 100644
--- a/kitty/fast_data_types.pyi
+++ b/kitty/fast_data_types.pyi
@@ -1724,6 +1724,7 @@ def buffer_keys_in_window(os_window_id: int, tab_id: int, window_id: int, enable
 def sprite_idx_to_pos(idx: int, xnum: int, ynum: int) -> tuple[int, int, int]: ...
 def render_box_char(ch: int, width: int, height: int, scale: float = 1.0, dpi_x: float = 96.0, dpi_y: float = 96.0) -> bytes: ...
 def run_at_exit_cleanup_functions() -> None: ...
+def render_decoration(which: str, cell_width: int, cell_height: int, underline_position: int, underline_thickness: int) -> bytes: ...
 
 class MousePosition(TypedDict):
     cell_x: int
diff --git a/kitty/fonts.c b/kitty/fonts.c
index e2e5a420f..6ea6eb6ee 100644
--- a/kitty/fonts.c
+++ b/kitty/fonts.c
@@ -2107,6 +2107,18 @@ alpha_blend(uint32_t fg, uint32_t bg) {
     return (0xff000000) | (r << 16) | (g << 8) | b;
 }
 
+static PyObject*
+render_decoration(PyObject *self UNUSED, PyObject *args) {
+    const char *which;
+    FontCellMetrics fcm = {0};
+    if (!PyArg_ParseTuple(args, "sIIII", &which, &fcm.cell_width, &fcm.cell_height, &fcm.underline_position, &fcm.underline_thickness)) return NULL;
+    PyObject *ans = PyBytes_FromStringAndSize(NULL, fcm.cell_width * fcm.cell_height);
+    if (!ans) return NULL;
+    memset(PyBytes_AS_STRING(ans), 0, PyBytes_GET_SIZE(ans));
+    if (strcmp(which, "curl") == 0) add_curl_underline((uint8_t*)PyBytes_AS_STRING(ans), fcm);
+    return ans;
+}
+
 static PyObject*
 concat_cells(PyObject UNUSED *self, PyObject *args) {
     // Concatenate cells returning RGBA data
@@ -2334,6 +2346,7 @@ static PyMethodDef module_methods[] = {
     METHODB(sprite_map_set_layout, METH_VARARGS),
     METHODB(test_sprite_position_increment, METH_NOARGS),
     METHODB(concat_cells, METH_VARARGS),
+    METHODB(render_decoration, METH_VARARGS),
     METHODB(set_send_sprite_to_gpu, METH_O),
     METHODB(set_allow_use_of_box_fonts, METH_O),
     METHODB(test_shape, METH_VARARGS),
diff --git a/kitty/fonts/render.py b/kitty/fonts/render.py
index 1a20e6cb4..1254d4663 100644
--- a/kitty/fonts/render.py
+++ b/kitty/fonts/render.py
@@ -10,9 +10,11 @@ from typing import TYPE_CHECKING, Any, Literal, Union
 from kitty.constants import fonts_dir, is_macos
 from kitty.fast_data_types import (
     Screen,
+    concat_cells,
     create_test_font_group,
     current_fonts,
     get_fallback_font,
+    render_decoration,
     set_builtin_nerd_font,
     set_font_data,
     set_options,
@@ -319,7 +321,6 @@ def test_render_string(
         size: float = 64.0,
         dpi: float = 96.0
 ) -> None:
-    from kitty.fast_data_types import concat_cells, current_fonts
 
     cell_width, cell_height, cells = render_string(text, family, size, dpi)
     rgb_data = concat_cells(cell_width, cell_height, True, tuple(cells))
@@ -373,3 +374,10 @@ def test_render_codepoint(chars: str = '😺', path: str = '/t/Noto-COLRv1.ttf',
         print('Rendered:', char)
         display_bitmap(bitmap, w, h)
         print('\n')
+
+
+def test_render_decoration(which: Literal['curl'], cell_width: int, cell_height: int, underline_position: int, underline_thickness: int) -> None:
+    buf = render_decoration(which, cell_width, cell_height, underline_position, underline_thickness)
+    cells = buf, buf, buf, buf, buf
+    rgb_data = concat_cells(cell_width, cell_height, False, cells)
+    display_bitmap(rgb_data, cell_width * len(cells), cell_height)