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lavfi/vf_drawtext: log inferred shaping properties at verbose

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Log the script and direction picked by HarfBuzz, plus codepoint and
glyph counts, so the shaper choice can be verified. Differing
codepoint and glyph counts indicate reordering / ligation /
decomposition.

Codepoints are sampled before hb_shape(), which flips the buffer
content type to GLYPHS.

Signed-off-by: Jun Zhao <barryjzhao@tencent.com>
This commit is contained in:
Jun Zhao
2026-06-02 00:52:03 +00:00
committed by Jun Zhao
co-authored by Jun Zhao
parent 1f9888beb0
commit d092269996
1 changed files with 20 additions and 3 deletions
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libavfilter/vf_drawtext.c
+20 -3
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@@ -1368,8 +1368,11 @@ static int draw_glyphs(AVFilterContext *ctx, AVFrame *frame,
}
// Shapes a line of text using libharfbuzz
static int shape_text_hb(DrawTextContext *s, HarfbuzzData* hb, const char* text, int textLen)
static int shape_text_hb(AVFilterContext *ctx, DrawTextContext *s,
HarfbuzzData *hb, const char *text, int textLen)
{
unsigned codepoints;
hb->buf = hb_buffer_create();
if (!hb_buffer_allocation_successful(hb->buf))
goto fail;
@@ -1382,6 +1385,9 @@ static int shape_text_hb(DrawTextContext *s, HarfbuzzData* hb, const char* text,
hb_buffer_set_direction(hb->buf, HB_DIRECTION_LTR);
hb_buffer_set_language(hb->buf, hb_language_from_string("en", -1));
hb_buffer_guess_segment_properties(hb->buf);
/* Sample the buffer length here, before hb_shape() flips the buffer's
* content type from UNICODE to GLYPHS. */
codepoints = hb_buffer_get_length(hb->buf);
hb->font = hb_ft_font_create_referenced(s->face);
if (hb->font == NULL)
goto fail;
@@ -1389,6 +1395,17 @@ static int shape_text_hb(DrawTextContext *s, HarfbuzzData* hb, const char* text,
hb->glyph_info = hb_buffer_get_glyph_infos(hb->buf, &hb->glyph_count);
hb->glyph_pos = hb_buffer_get_glyph_positions(hb->buf, &hb->glyph_count);
if (av_log_get_level() >= AV_LOG_VERBOSE) {
char script_tag[5] = { 0 };
hb_script_t script = hb_buffer_get_script(hb->buf);
hb_direction_t dir = hb_buffer_get_direction(hb->buf);
hb_tag_to_string(hb_script_to_iso15924_tag(script), script_tag);
av_log(ctx, AV_LOG_VERBOSE,
"shape: script=%s direction=%s codepoints=%u glyphs=%u\n",
script_tag, hb_direction_to_string(dir),
codepoints, hb->glyph_count);
}
return 0;
fail:
hb_buffer_destroy(hb->buf);
@@ -1441,7 +1458,7 @@ continue_on_failed:
// Evaluate the width of the space character if needed to replace tabs
if (s->tab_count > 0 && !s->blank_advance64) {
HarfbuzzData hb_data;
ret = shape_text_hb(s, &hb_data, " ", 1);
ret = shape_text_hb(ctx, s, &hb_data, " ", 1);
if(ret != 0) {
goto done;
}
@@ -1479,7 +1496,7 @@ continue_on_failed2:
TextLine *cur_line = &s->lines[line_count];
HarfbuzzData *hb = &cur_line->hb_data;
cur_line->cluster_offset = line_offset;
ret = shape_text_hb(s, hb, start, len);
ret = shape_text_hb(ctx, s, hb, start, len);
if (ret != 0) {
goto done;
}