[autofit] Add GSUB table handling to reverse character map generation.
If HarfBuzz is enabled, the reverse character map generation now considers GSUB entries when looking for glyphs that correspond to a code point. * src/autofit/afadjust.c (af_all_glyph_variants_helper, af_all_glyph_variants) [FT_CONFIG_OPTION_USE_HARFBUZZ]: New functions. (af_reverse_character_map_new) [FT_CONFIG_OPTION_USE_HARFBUZZ]: Call new code.
This commit is contained in:
Craig White
Werner Lemberg
parent
48491c67e5
commit
74d9a996ae
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@ -327,6 +327,349 @@
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}
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#ifdef FT_CONFIG_OPTION_USE_HARFBUZZ
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/*
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Recursive algorithm to find all glyphs that a code point could turn into
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from the 'GSUB' table.
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buffer: a buffer containing only the input code point
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feature_tag_pool: the current list of features under consideration
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current_features: the current list of features being applied
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num_features: length of current_features
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result: the set of glyphs that the input code point can map to
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The algorithm works by running the `hb_ot_shape_glyphs_closure` function
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on different lists of features to check which features map the glyph onto
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something different. This function returns the result of transforming a
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glyph using a list of features as well as all intermediate forms if the
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glyph was transformed multiple times.
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With no features enabled, `hb_ot_shape_glyphs_closure` only returns the
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glyph given by the cmap. This character is the first to be placed into
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the result set.
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Next, the algorithm tests the same lookup enabling one feature at a time
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and check whether any of those features change the result.
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If any new glyph variants are found this way, they are added to the
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result set and the algorithm recurses, trying that feature in combination
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with every other feature to look for further glyph variants.
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Example:
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suppose we have the following features in the GSUB table:
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f1: a -> b
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f2: b -> c
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f3: d -> e
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The algorithm takes the following steps to find all variants of 'a'.
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- Add 'a' to the result.
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- Look up with feature list {f1}, yielding {a, b}.
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=> Add 'b' to the result list, recurse.
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- Look up with feature list {f1, f2}, yielding {a, b, c}.
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=> Add 'c' to the result list, recurse.
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- Look up with feature list {f1, f2, f3}, yielding {a, b, c}.
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=> No new glyphs.
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- Look up with feature list {f1, f3}, yielding {a, b}.
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=> No new glyphs.
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- Look up with feature list {f2}, yielding {a}.
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=> No new glyphs.
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- Look up with feature list {f3}, yielding {a}.
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=> No new glyphs.
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*/
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static FT_Error
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af_all_glyph_variants_helper( hb_font_t *font,
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hb_buffer_t *buffer,
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hb_set_t *feature_tag_pool,
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hb_feature_t *current_features,
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FT_UInt32 num_features,
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hb_set_t* result )
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{
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FT_Error error;
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hb_set_t *baseline_glyphs = NULL;
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hb_set_t *new_glyphs = NULL;
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hb_tag_t feature_tag;
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/* Get the list of glyphs that are created by only transforming, */
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/* based on the features in `current_features`. */
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baseline_glyphs = hb_set_create();
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if ( !hb_set_allocation_successful( baseline_glyphs ) )
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{
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error = FT_Err_Out_Of_Memory;
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goto Exit;
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}
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hb_ot_shape_glyphs_closure( font,
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buffer,
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current_features,
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num_features,
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baseline_glyphs );
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if ( !hb_set_allocation_successful( baseline_glyphs ) )
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{
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error = FT_Err_Out_Of_Memory;
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goto Exit;
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}
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/* Add these baseline glyphs to the result. The baseline glyph set */
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/* contains at least the glyph specified by the cmap. */
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hb_set_union( result, baseline_glyphs );
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if ( !hb_set_allocation_successful( result ) )
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{
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error = FT_Err_Out_Of_Memory;
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goto Exit;
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}
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if ( !hb_set_get_population( feature_tag_pool ) )
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{
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error = FT_Err_Out_Of_Memory;
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goto Exit;
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}
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/* Prepare for adding different features to `current_features` to */
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/* check whether any of them have an effect of the glyphs we get from */
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/* `hb_ot_shape_glyphs_closure`. */
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current_features[num_features].start = HB_FEATURE_GLOBAL_START;
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current_features[num_features].end = HB_FEATURE_GLOBAL_END;
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current_features[num_features].value = 1; /* enable the feature */
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/*
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Quote from the HarfBuzz documentation about the `value` attribute:
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0 disables the feature, non-zero (usually 1) enables the feature.
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For features implemented as lookup type 3 (like 'salt') the value is
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a one-based index into the alternates. This algorithm does not
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handle these lookup type 3 cases fully.
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*/
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new_glyphs = hb_set_create();
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if ( !hb_set_allocation_successful( new_glyphs ) )
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{
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error = FT_Err_Out_Of_Memory;
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goto Exit;
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}
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feature_tag = HB_SET_VALUE_INVALID;
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while ( hb_set_next( feature_tag_pool, &feature_tag ) )
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{
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hb_set_clear( new_glyphs );
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current_features[num_features].tag = feature_tag;
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hb_ot_shape_glyphs_closure ( font,
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buffer,
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current_features,
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num_features + 1,
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new_glyphs );
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if ( !hb_set_allocation_successful( new_glyphs ) )
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{
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error = FT_Err_Out_Of_Memory;
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goto Exit;
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}
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hb_set_subtract( new_glyphs, result );
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/* `new_glyphs` now contains all glyphs that appeared in the result */
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/* of `hb_ot_shape_glyphs_closure` that haven't already been */
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/* accounted for in the result. If this contains any glyphs, we */
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/* also need to try this feature in combination with other features */
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/* by recursing. */
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if ( hb_set_get_population( new_glyphs ) != 0 )
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{
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/* Remove this feature from the feature pool temporarily so that */
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/* a later recursion won't try it. */
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hb_set_del( feature_tag_pool, feature_tag );
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error = af_all_glyph_variants_helper( font,
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buffer,
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feature_tag_pool,
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current_features,
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num_features + 1,
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result );
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if ( error )
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goto Exit;
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/* Add back the feature we removed. */
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hb_set_add( feature_tag_pool, feature_tag );
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if ( !hb_set_allocation_successful( feature_tag_pool ) )
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return FT_Err_Out_Of_Memory;
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}
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}
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Exit:
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hb_set_destroy( baseline_glyphs );
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hb_set_destroy( new_glyphs );
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return FT_Err_Ok;
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}
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static FT_Error
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af_all_glyph_variants( FT_Face face,
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hb_font_t *hb_font,
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FT_UInt32 codepoint,
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hb_set_t* result )
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{
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FT_Error error;
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FT_Memory memory = face->memory;
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hb_face_t *hb_face = hb_font_get_face( hb_font );
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FT_Bool feature_list_done;
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unsigned int start_offset;
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/* The set of all feature tags in the font. */
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hb_set_t *feature_tags = hb_set_create();
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hb_set_t *type_3_lookup_indices = hb_set_create();
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hb_buffer_t *codepoint_buffer = hb_buffer_create();
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hb_codepoint_t *type_3_alternate_glyphs_buffer;
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hb_feature_t *feature_buffer;
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/* List of features containing type 3 lookups. */
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hb_tag_t feature_list[] =
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{
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HB_TAG( 's', 'a', 'l', 't' ),
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HB_TAG( 's', 'w', 's', 'h' ),
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HB_TAG( 'n', 'a', 'l', 't' ),
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HB_TAG_NONE
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};
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hb_codepoint_t lookup_index;
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FT_UInt base_glyph_index;
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if ( !hb_set_allocation_successful( feature_tags ) ||
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!hb_buffer_allocation_successful( codepoint_buffer ) ||
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!hb_set_allocation_successful ( type_3_lookup_indices ) )
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{
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error = FT_Err_Out_Of_Memory;
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goto Exit;
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}
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/* Populate `feature_tags` using the output of */
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/* `hb_ot_layout_table_get_feature_tags`. */
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feature_list_done = 0;
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start_offset = 0;
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while ( !feature_list_done )
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{
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unsigned int feature_count = 20;
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hb_tag_t tags[20];
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unsigned int i;
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hb_ot_layout_table_get_feature_tags( hb_face,
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HB_OT_TAG_GSUB,
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start_offset,
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&feature_count,
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tags );
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start_offset += 20;
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if ( feature_count < 20 )
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feature_list_done = 1;
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for ( i = 0; i < feature_count; i++ )
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hb_set_add( feature_tags, tags[i] );
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if ( !hb_set_allocation_successful( feature_tags ) )
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{
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error = FT_Err_Out_Of_Memory;
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goto Exit;
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}
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}
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/* Make a buffer only consisting of the given code point. */
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if ( !hb_buffer_pre_allocate( codepoint_buffer, 1 ) )
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{
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error = FT_Err_Out_Of_Memory;
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goto Exit;
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}
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hb_buffer_set_direction( codepoint_buffer, HB_DIRECTION_LTR );
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hb_buffer_add( codepoint_buffer, codepoint, 0 );
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/* The array of features that is used by the recursive part has at */
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/* most as many entries as there are features, so make the length */
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/* equal to the length of `feature_tags`. */
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if ( ( error = FT_NEW_ARRAY( feature_buffer,
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hb_set_get_population( feature_tags ) ) ) )
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goto Exit;
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error = af_all_glyph_variants_helper( hb_font,
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codepoint_buffer,
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feature_tags,
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feature_buffer,
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0,
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result );
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if ( error )
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goto Exit;
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/* Add the alternative glyph forms that come from features using
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type 3 lookups.
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This file from gtk was very useful in figuring out my approach:
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https://gitlab.gnome.org/GNOME/gtk/-/blob/40f20fee3d8468749dfb233a6f95921c765c1163/gtk/gtkfontchooserwidget.c#L2100
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*/
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hb_ot_layout_collect_lookups( hb_face,
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HB_OT_TAG_GSUB,
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NULL,
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NULL,
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feature_list,
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type_3_lookup_indices );
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if ( !hb_set_allocation_successful( type_3_lookup_indices ) )
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{
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error = FT_Err_Out_Of_Memory;
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goto Exit;
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}
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#define MAX_ALTERNATES 100 /* ad-hoc value */
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if ( ( error = FT_NEW_ARRAY( type_3_alternate_glyphs_buffer,
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MAX_ALTERNATES ) ) )
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goto Exit;
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lookup_index = HB_SET_VALUE_INVALID;
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base_glyph_index = FT_Get_Char_Index( face, codepoint );
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if ( base_glyph_index )
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{
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while ( hb_set_next( type_3_lookup_indices, &lookup_index ) )
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{
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unsigned alternate_count = MAX_ALTERNATES;
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unsigned i;
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hb_ot_layout_lookup_get_glyph_alternates(
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hb_face,
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lookup_index,
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base_glyph_index,
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0,
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&alternate_count,
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type_3_alternate_glyphs_buffer );
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for ( i = 0; i < alternate_count; i++ )
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hb_set_add( result, type_3_alternate_glyphs_buffer[i] );
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}
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}
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Exit:
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hb_set_destroy( feature_tags );
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hb_buffer_destroy( codepoint_buffer );
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FT_FREE( feature_buffer );
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FT_FREE( type_3_alternate_glyphs_buffer );
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return error;
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}
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#endif /*FT_CONFIG_OPTION_USE_HARFBUZZ*/
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FT_LOCAL_DEF( FT_Error )
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af_reverse_character_map_new( AF_ReverseCharacterMap *map,
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AF_FaceGlobals globals )
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@ -364,6 +707,66 @@
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if ( FT_NEW_ARRAY( ( *map )->entries, capacity ) )
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goto Exit;
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#ifdef FT_CONFIG_OPTION_USE_HARFBUZZ
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{
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hb_font_t *hb_font = globals->hb_font;
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hb_set_t *result_set = hb_set_create();
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FT_ULong i;
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if ( !hb_set_allocation_successful( result_set ) )
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{
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error = FT_Err_Out_Of_Memory;
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goto harfbuzz_path_Exit;
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}
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/* Find all glyph variants of the code points, then make an entry */
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/* from the glyph to the code point for each one. */
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for ( i = 0; i < AF_ADJUSTMENT_DATABASE_LENGTH; i++ )
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{
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FT_UInt32 codepoint = adjustment_database[i].codepoint;
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hb_codepoint_t glyph;
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error = af_all_glyph_variants( face,
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hb_font,
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codepoint,
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result_set );
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if ( error )
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goto harfbuzz_path_Exit;
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glyph = HB_SET_VALUE_INVALID;
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while ( hb_set_next( result_set, &glyph ) )
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{
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FT_Long insert_point;
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error = af_reverse_character_map_expand( *map, &capacity, memory );
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if ( error )
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goto harfbuzz_path_Exit;
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insert_point = ( *map )->length;
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( *map )->length++;
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( *map )->entries[insert_point].glyph_index = glyph;
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( *map )->entries[insert_point].codepoint = codepoint;
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}
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hb_set_clear( result_set );
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}
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harfbuzz_path_Exit:
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hb_set_destroy( result_set );
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if ( error )
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goto Exit;
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}
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#else /* !FT_CONFIG_OPTION_USE_HARFBUZZ */
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{
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FT_UInt i;
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#ifdef FT_DEBUG_LEVEL_TRACE
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@ -395,6 +798,8 @@
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}
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}
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#endif /* !FT_CONFIG_OPTION_USE_HARFBUZZ */
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ft_qsort( ( *map )->entries,
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( *map )->length,
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sizeof ( AF_ReverseMapEntry ),
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