Segment.h

/* SPDX-License-Identifier: MIT OR MPL-2.0 OR LGPL-2.1-or-later OR GPL-2.0-or-later */
/* Copyright 2010, SIL International, All rights reserved. */
#pragma once

#include "graphite2/Types.h"
#include "graphite2/Font.h"

#ifdef __cplusplus
extern "C"
{
#endif

enum gr_break_weight {
    gr_breakNone = 0,
    /* after break weights */
    gr_breakWhitespace = 10,
    gr_breakWord = 15,
    gr_breakIntra = 20,
    gr_breakLetter = 30,
    gr_breakClip = 40,
    /* before break weights */
    gr_breakBeforeWhitespace = -10,
    gr_breakBeforeWord = -15,
    gr_breakBeforeIntra = -20,
    gr_breakBeforeLetter = -30,
    gr_breakBeforeClip = -40
};

enum gr_justFlags {
    /// Indicates that this segment is a complete line
    gr_justCompleteLine = 0,
    /// Indicates that the start of the slot list is not at the start of a line
    gr_justStartInline = 1,
    /// Indicates that the end of the slot list is not at the end of a line
    gr_justEndInline = 2
};

/** Used for looking up slot attributes. Most are already available in other functions **/
enum gr_attrCode {
    /// adjusted glyph advance in x direction in design units
    gr_slatAdvX = 0,
    /// adjusted glyph advance in y direction (usually 0) in design units
    gr_slatAdvY,
    /// returns 0. Deprecated.
    gr_slatAttTo,
    /// This slot attaches to its parent at the given design units in the x direction
    gr_slatAttX,
    /// This slot attaches to its parent at the given design units in the y direction
    gr_slatAttY,
    /// This slot attaches to its parent at the given glyph point (not implemented)
    gr_slatAttGpt,
    /// x-direction adjustment from the given glyph point (not implemented)
    gr_slatAttXOff,
    /// y-direction adjustment from the given glyph point (not implemented)
    gr_slatAttYOff,
    /// Where on this glyph should align with the attachment point on the parent glyph in the x-direction.
    gr_slatAttWithX,
    /// Where on this glyph should align with the attachment point on the parent glyph in the y-direction
    gr_slatAttWithY,
    /// Which glyph point on this glyph should align with the attachment point on the parent glyph (not implemented).
    gr_slatWithGpt,
    /// Adjustment to gr_slatWithGpt in x-direction (not implemented)
    gr_slatAttWithXOff,
    /// Adjustment to gr_slatWithGpt in y-direction (not implemented)
    gr_slatAttWithYOff,
    /// Attach at given nesting level (not implemented)
    gr_slatAttLevel,
    /// Line break breakweight for this glyph
    gr_slatBreak,
    /// Ligature component reference (not implemented)
    gr_slatCompRef,
    /// bidi directionality of this glyph (not implemented)
    gr_slatDir,
    /// Whether insertion is allowed before this glyph
    gr_slatInsert,
    /// Final positioned position of this glyph relative to its parent in x-direction in pixels
    gr_slatPosX,
    /// Final positioned position of this glyph relative to its parent in y-direction in pixels
    gr_slatPosY,
    /// Amount to shift glyph by in x-direction design units
    gr_slatShiftX,
    /// Amount to shift glyph by in y-direction design units
    gr_slatShiftY,
    /// attribute user1
    gr_slatUserDefnV1,
    /// not implemented
    gr_slatMeasureSol,
    /// not implemented
    gr_slatMeasureEol,
    /// Amount this slot can stretch (not implemented)
    gr_slatJStretch,
    /// Amount this slot can shrink (not implemented)
    gr_slatJShrink,
    /// Granularity by which this slot can stretch or shrink (not implemented)
    gr_slatJStep,
    /// Justification weight for this glyph (not implemented)
    gr_slatJWeight,
    /// Amount this slot mush shrink or stretch in design units
    gr_slatJWidth = 29,
    /// SubSegment split point
    gr_slatSegSplit = gr_slatJStretch + 29,
    /// User defined attribute, see subattr for user attr number
    gr_slatUserDefn,
    /// Bidi level
    gr_slatBidiLevel = 56,
    /// Collision flags
    gr_slatColFlags,
    /// Collision constraint rectangle left (bl.x)
    gr_slatColLimitblx,
    /// Collision constraint rectangle lower (bl.y)
    gr_slatColLimitbly,
    /// Collision constraint rectangle right (tr.x)
    gr_slatColLimittrx,
    /// Collision constraint rectangle upper (tr.y)
    gr_slatColLimittry,
    /// Collision shift x
    gr_slatColShiftx,
    /// Collision shift y
    gr_slatColShifty,
    /// Collision margin
    gr_slatColMargin,
    /// Margin cost weight
    gr_slatColMarginWt,
    // Additional glyph that excludes movement near this one:
    gr_slatColExclGlyph,
    gr_slatColExclOffx,
    gr_slatColExclOffy,
    // Collision sequence enforcing attributes:
    gr_slatSeqClass,
    gr_slatSeqProxClass,
    gr_slatSeqOrder,
    gr_slatSeqAboveXoff,
    gr_slatSeqAboveWt,
    gr_slatSeqBelowXlim,
    gr_slatSeqBelowWt,
    gr_slatSeqValignHt,
    gr_slatSeqValignWt,

    /// not implemented
    gr_slatMax,
    /// not implemented
    gr_slatNoEffect = gr_slatMax + 1
};

enum gr_bidirtl {
    /// Underlying paragraph direction is RTL
    gr_rtl = 1,
    /// Set this to not run the bidi pass internally, even if the font asks for it.
    /// This presumes that the segment is in a single direction. Most of the time
    /// this bit should be set unless you know you are passing full paragraphs of text.
    gr_nobidi = 2,
    /// Disable auto mirroring for rtl text
    gr_nomirror = 4
};

typedef struct gr_char_info     gr_char_info;
typedef struct gr_segment       gr_segment;
typedef struct gr_slot          gr_slot;

/** Returns Unicode character for a charinfo.
  *
  * @param p Pointer to charinfo to return information on.
  */
GR2_API unsigned int gr_cinfo_unicode_char(const gr_char_info* p/*not NULL*/);

/** Returns breakweight for a charinfo.
  *
  * @return Breakweight is a number between -50 and 50 indicating the cost of a
  * break before or after this character. If the value < 0, the absolute value
  * is this character's contribution to the overall breakweight before it. If the value
  * > 0, then the value is this character's contribution to the overall breakweight after it.
  * The overall breakweight between two characters is the maximum of the breakweight
  * contributions from the characters either side of it. If a character makes no
  * contribution to the breakweight on one side of it, the contribution is considered
  * to be 0.
  * @param p Pointer to charinfo to return information on.
  */
GR2_API int gr_cinfo_break_weight(const gr_char_info* p/*not NULL*/);

/** Returns the slot index that after this character is after in the slot stream
  *
  * In effect each character is associated with a set of slots and this returns
  * the index of the last slot in the segment this character is associated with.
  *
  * @return after slot index between 0 and gr_seg_n_slots()
  * @param p Pointer to charinfo to return information on.
  */
GR2_API int gr_cinfo_after(const gr_char_info* p/*not NULL*/);

/** Returns the slot index that before this character is before in the slot stream
  *
  * In effect each character is associated with a set of slots and this returns
  * the index of the first slot in the segment this character is associated with.
  *
  * @return before slot index between 0 and gr_seg_n_slots()
  * @param p Pointer to charinfo to return information on.
  */
GR2_API int gr_cinfo_before(const gr_char_info* p/*not NULL*/);

/** Returns the code unit index of this character in the input string
  *
  * @return code unit index between 0 and the end of the string
  * @param p Pointer to charinfo to return information on.
  */
GR2_API size_t gr_cinfo_base(const gr_char_info* p/*not NULL*/);

/** Returns the number of unicode characters in a string.
  *
  * @return number of characters in the string
  * @param enc Specifies the type of data in the string: utf8, utf16, utf32
  * @param buffer_begin The start of the string
  * @param buffer_end Measure up to the first nul or when end is reached, whichever is earliest.
  *            This parameter may be NULL.
  * @param pError If there is a structural fault in the string, the location is returned
  *               in this variable. If no error occurs, pError will contain NULL. NULL
  *               may be passed for pError if no such information is required.
  */
GR2_API size_t gr_count_unicode_characters(enum gr_encform enc, const void* buffer_begin, const void* buffer_end, const void** pError);

/** Creates and returns a segment.
  *
  * @return a segment that needs seg_destroy called on it. May return NULL if bad problems
  *     in segment processing.
  * @param font Gives the size of the font in pixels per em for final positioning. If
  *             NULL, positions are returned in design units, i.e. at a ppm of the upem
  *             of the face.
  * @param face The face containing all the non-size dependent information.
  * @param script This is a tag containing a script identifier that is used to choose
  *               which graphite table within the font to use. Maybe 0. Tag may be 4 chars
  *               NULL padded in LSBs or space padded in LSBs.
  * @param pFeats Pointer to a feature values to be used for the segment. Only one
  *               feature values may be used for a segment. If NULL the default features
  *               for the font will be used.
  * @param enc Specifies what encoding form the string is in (utf8, utf16, utf32)
  * @param pStart Start of the string
  * @param nChars Number of unicode characters to process in the string. The string will
  *               be processed either up to the first NULL or until nChars have been
  *               processed. nChars is also used to initialise the internal memory
  *               allocations of the segment. So it is wise not to make nChars too much
  *               greater than the actual number of characters being processed.
  * @param dir Specifies whether the segment is processed right to left (1) or left to
  *            right (0) and whether to run the internal bidi pass, if a font requests it.
  *            See enum gr_bidirtl for details.
  */
GR2_API gr_segment* gr_make_seg(const gr_font* font, const gr_face* face, gr_uint32 script, const gr_feature_val* pFeats, enum gr_encform enc, const void* pStart, size_t nChars, int dir);

/** Destroys a segment, freeing the memory.
  *
  * @param p The segment to destroy
  */
GR2_API void gr_seg_destroy(gr_segment* p);

/** Returns the advance for the whole segment.
  *
  * Returns the width of the segment up to the next glyph origin after the segment
  */
GR2_API float gr_seg_advance_X(const gr_segment* pSeg/*not NULL*/);

/** Returns the height advance for the segment. **/
GR2_API float gr_seg_advance_Y(const gr_segment* pSeg/*not NULL*/);

/** Returns the number of gr_char_infos in the segment. **/
GR2_API unsigned int gr_seg_n_cinfo(const gr_segment* pSeg/*not NULL*/);

/** Returns a gr_char_info at a given index in the segment. **/
GR2_API const gr_char_info* gr_seg_cinfo(const gr_segment* pSeg/*not NULL*/, unsigned int index/*must be <number_of_CharInfo*/);

/** Returns the number of glyph gr_slots in the segment. **/
GR2_API unsigned int gr_seg_n_slots(const gr_segment* pSeg/*not NULL*/);      //one slot per glyph

/** Returns the first gr_slot in the segment.
  *
  * The first slot in a segment has a gr_slot_prev_in_segment() of NULL. Slots are owned
  * by their segment and are destroyed along with the segment.
  */
GR2_API const gr_slot* gr_seg_first_slot(gr_segment* pSeg/*not NULL*/);    //may give a base slot or a slot which is attached to another

/** Returns the last gr_slot in the segment.
  *
  * The last slot in a segment has a gr_slot_next_in_segment() of NULL
  */
GR2_API const gr_slot* gr_seg_last_slot(gr_segment* pSeg/*not NULL*/);    //may give a base slot or a slot which is attached to another

/** Justifies a linked list of slots for a line to a given width
  *
  * Passed a pointer to the start of a linked list of slots corresponding to a line, as
  * set up by gr_slot_linebreak_before, this function will position the glyphs in the line
  * to take up the given width. It is possible to specify a subrange within the line to process.
  * This allows skipping of line initial or final whitespace, for example. While this will ensure
  * that the subrange fits width, the line will still be positioned with the first glyph of the
  * line at 0. So the resulting positions may be beyond width.
  *
  * @return float   The resulting width of the range of slots justified.
  * @param pSeg     Pointer to the segment
  * @param pStart   Pointer to the start of the line linked list (including skipped characters)
  * @param pFont    Font to use for positioning
  * @param width    Width in pixels in which to fit the line. If < 0. don't adjust natural width, just run justification passes
  *                 to handle line end contextuals, if there are any.
  * @param flags    Indicates line ending types. Default is linked list is a full line
  * @param pFirst   If not NULL, the first slot in the list to be considered part of the line (so can skip)
  * @param pLast    If not NULL, the last slot to process in the line (allow say trailing whitespace to be skipped)
  */
GR2_API float gr_seg_justify(gr_segment* pSeg/*not NULL*/, const gr_slot* pStart/*not NULL*/, const gr_font *pFont, double width, enum gr_justFlags flags, const gr_slot* pFirst, const gr_slot* pLast);

/** Returns the next slot along in the segment.
  *
  * Slots are held in a linked list. This returns the next in the linked list. The slot
  * may or may not be attached to another slot. Returns NULL at the end of the segment.
  */
GR2_API const gr_slot* gr_slot_next_in_segment(const gr_slot* p);

/** Returns the previous slot along in the segment.
  *
  * Slots are held in a doubly linked list. This returns the previos slot in the linked
  * list. This slot may or may not be attached to it. Returns NULL at the start of the
  * segment.
  */
GR2_API const gr_slot* gr_slot_prev_in_segment(const gr_slot* p);

/** Returns the attachment parent slot of this slot.
  *
  * Attached slots form a tree. This returns the parent of this slot in that tree. A
  * base glyph which is not attached to another glyph, always returns NULL.
  */
GR2_API const gr_slot* gr_slot_attached_to(const gr_slot* p);

/** Returns the first slot attached to this slot.
  *
  * Attached slots form a singly linked list from the parent. This returns the first
  * slot in that list. Note that this is a reference to another slot that is also in
  * the main segment doubly linked list.
  *
  * if gr_slot_first_attachment(p) != NULL then gr_slot_attached_to(gr_slot_first_attachment(p)) == p.
  */
GR2_API const gr_slot* gr_slot_first_attachment(const gr_slot* p);

/** Returns the next slot attached to our attachment parent.
  *
  * This returns the next slot in the singly linked list of slots attached to this
  * slot's parent. If there are no more such slots, NULL is returned. If there is
  * no parent, i.e. the passed slot is a cluster base, then the next cluster base
  * in graphical order (ltr, even for rtl text) is returned.
  *
  * if gr_slot_next_sibling_attachment(p) != NULL then gr_slot_attached_to(gr_slot_next_sibling_attachment(p)) == gr_slot_attached_to(p).
  */
GR2_API const gr_slot* gr_slot_next_sibling_attachment(const gr_slot* p);


/** Returns glyph id of the slot
  *
  * Each slot has a glyphid which is rendered at the position given by the slot. This
  * glyphid is the real glyph to be rendered and never a pseudo glyph.
  */
GR2_API unsigned short gr_slot_gid(const gr_slot* p);

/** Returns X offset of glyph from start of segment **/
GR2_API float gr_slot_origin_X(const gr_slot* p);

/** Returns Y offset of glyph from start of segment **/
GR2_API float gr_slot_origin_Y(const gr_slot* p);

/** Returns the glyph advance for this glyph as adjusted for kerning
  *
  * @param p    Slot to give results for
  * @param face gr_face of the glyphs. May be NULL if unhinted advances used
  * @param font gr_font to scale for pixel results. If NULL returns design
  *             units advance. If not NULL then returns pixel advance based
  *             on hinted or scaled glyph advances in the font. face must be
  *             passed for hinted advances to be used.
  */
GR2_API float gr_slot_advance_X(const gr_slot* p, const gr_face* face, const gr_font *font);

/** Returns the vertical advance for the glyph in the slot adjusted for kerning
  *
  * Returns design units unless font is not NULL in which case the pixel value
  * is returned scaled for the given font
  */
GR2_API float gr_slot_advance_Y(const gr_slot* p, const gr_face* face, const gr_font *font);

/** Returns the gr_char_info index before us
  *
  * Returns the index of the gr_char_info that a cursor before this slot, would put
  * an underlying cursor before. This may also be interpretted as each slot holding
  * a set of char_infos that it is associated with and this function returning the
  * index of the char_info with lowest index, from this set.
  */
GR2_API int gr_slot_before(const gr_slot* p/*not NULL*/);

/** Returns the gr_char_info index after us
  *
  * Returns the index of the gr_char_info that a cursor after this slot would put an
  * underlying cursor after. This may also be interpretted as each slot holding a set
  * of char_infos that it is associated with and this function returning the index of
  * the char_info with the highest index, from this set.
  */
GR2_API int gr_slot_after(const gr_slot* p/*not NULL*/);

/** Returns the index of this slot in the segment
  *
  * Returns the index given to this slot during final positioning. This corresponds
  * to the value returned br gr_cinfo_before() and gr_cinfo_after()
  */
GR2_API unsigned int gr_slot_index(const gr_slot* p/*not NULL*/);

/** Return a slot attribute value
  *
  * Given a slot and an attribute along with a possible subattribute, return the
  * corresponding value in the slot. See enum gr_attrCode for details of each attribute.
  */
GR2_API int gr_slot_attr(const gr_slot* p/*not NULL*/, const gr_segment* pSeg/*not NULL*/, enum gr_attrCode index, gr_uint8 subindex); //tbd - do we need to expose this?

/** Returns whether text may be inserted before this glyph.
  *
  * This indicates whether a cursor can be put before this slot. It applies to
  * base glyphs that have no parent as well as attached glyphs that have the
  * .insert attribute explicitly set to true. This is the primary mechanism
  * for identifying contiguous sequences of base plus diacritics.
  */
GR2_API int gr_slot_can_insert_before(const gr_slot* p);

/** Returns the original gr_char_info index this slot refers to.
  *
  * Each Slot has a gr_char_info that it originates from. This is that gr_char_info.
  * The index is passed to gr_seg_cinfo(). This information is useful for testing.
  */
GR2_API int gr_slot_original(const gr_slot* p/*not NULL*/);

/** Breaks a segment into lines.
  *
  * Breaks the slot linked list at the given point in the linked list. It is up
  * to the application to keep track of the first slot on each line.
  */
GR2_API void gr_slot_linebreak_before(gr_slot *p/*not NULL*/);

#ifdef __cplusplus
}
#endif