layout_internal.h

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/*
 * Copyright 2003 James Bursa <bursa@users.sourceforge.net>
 *
 * This file is part of NetSurf, http://www.netsurf-browser.org/
 *
 * NetSurf is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; version 2 of the License.
 *
 * NetSurf is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
/**
 * \file
 * HTML layout private interface.
 */
 
#ifndef NETSURF_HTML_LAYOUT_INTERNAL_H
#define NETSURF_HTML_LAYOUT_INTERNAL_H
 
#define AUTO INT_MIN
 
/* Fixed point percentage (a) of an integer (b), to an integer */
#define FPCT_OF_INT_TOINT(a, b) (FIXTOINT(FDIV((a * b), F_100)))
 
/**
 * Layout a block formatting context.
 *
 * \param  block            BLOCK, INLINE_BLOCK, or TABLE_CELL to layout
 * \param  viewport_height  Height of viewport in pixels or -ve if unknown
 * \param  content          Memory pool for any new boxes
 * \return  true on success, false on memory exhaustion
 *
 * This function carries out layout of a block and its children, as described
 * in CSS 2.1 9.4.1.
 */
bool layout_block_context(
                struct box *block,
                int viewport_height,
                html_content *content);
 
/**
 * Layout a table.
 *
 * \param  table            table to layout
 * \param  available_width  width of containing block
 * \param  content          memory pool for any new boxes
 * \return  true on success, false on memory exhaustion
 */
bool layout_table(
                struct box *table,
                int available_width,
                html_content *content);
 
/**
 * Layout a flex container.
 *
 * \param[in] flex             table to layout
 * \param[in] available_width  width of containing block
 * \param[in] content          memory pool for any new boxes
 * \return  true on success, false on memory exhaustion
 */
bool layout_flex(
                struct box *flex,
                int available_width,
                html_content *content);
 
typedef uint8_t (*css_len_func)(
                const css_computed_style *style,
                css_fixed *length, css_unit *unit);
typedef uint8_t (*css_border_style_func)(
                const css_computed_style *style);
typedef uint8_t (*css_border_color_func)(
                const css_computed_style *style,
                css_color *color);
 
/** Array of per-side access functions for computed style margins. */
extern const css_len_func margin_funcs[4];
 
/** Array of per-side access functions for computed style paddings. */
extern const css_len_func padding_funcs[4];
 
/** Array of per-side access functions for computed style border_widths. */
extern const css_len_func border_width_funcs[4];
 
/** Array of per-side access functions for computed style border styles. */
extern const css_border_style_func border_style_funcs[4];
 
/** Array of per-side access functions for computed style border colors. */
extern const css_border_color_func border_color_funcs[4];
 
/** Layout helper: Check whether box is a float. */
static inline bool lh__box_is_float_box(const struct box *b)
{
        return b->type == BOX_FLOAT_LEFT ||
               b->type == BOX_FLOAT_RIGHT;
}
 
/** Layout helper: Check whether box takes part in inline flow. */
static inline bool lh__box_is_inline_flow(const struct box *b)
{
        return b->type == BOX_INLINE ||
               b->type == BOX_INLINE_FLEX ||
               b->type == BOX_INLINE_BLOCK ||
               b->type == BOX_TEXT ||
               b->type == BOX_INLINE_END;
}
 
/** Layout helper: Check whether box takes part in inline flow. */
static inline bool lh__box_is_flex_container(const struct box *b)
{
        return b->type == BOX_FLEX ||
               b->type == BOX_INLINE_FLEX;
}
 
/** Layout helper: Check whether box takes part in inline flow. */
static inline bool lh__box_is_flex_item(const struct box *b)
{
        return (b->parent != NULL) && lh__box_is_flex_container(b->parent);
}
 
/** Layout helper: Check whether box is inline level. (Includes BR.) */
static inline bool lh__box_is_inline_level(const struct box *b)
{
        return lh__box_is_inline_flow(b) ||
               b->type == BOX_BR;
}
 
/** Layout helper: Check whether box is inline level. (Includes BR, floats.) */
static inline bool lh__box_is_inline_content(const struct box *b)
{
        return lh__box_is_float_box(b) ||
               lh__box_is_inline_level(b);
}
 
/** Layout helper: Check whether box is an object. */
static inline bool lh__box_is_object(const struct box *b)
{
        return b->object ||
               (b->flags & (IFRAME | REPLACE_DIM));
}
 
/** Layout helper: Check whether box is replaced. */
static inline bool lh__box_is_replace(const struct box *b)
{
        return b->gadget ||
               lh__box_is_object(b);
}
 
/** Layout helper: Check for CSS border on given side. */
static inline bool lh__have_border(
                enum box_side side,
                const css_computed_style *style)
{
        return border_style_funcs[side](style) != CSS_BORDER_STYLE_NONE;
}
 
static inline bool lh__box_is_absolute(const struct box *b)
{
        return css_computed_position(b->style) == CSS_POSITION_ABSOLUTE ||
               css_computed_position(b->style) == CSS_POSITION_FIXED;
}
 
static inline bool lh__flex_main_is_horizontal(const struct box *flex)
{
        const css_computed_style *style = flex->style;
 
        assert(style != NULL);
 
        switch (css_computed_flex_direction(style)) {
        default:                        /* Fallthrough. */
        case CSS_FLEX_DIRECTION_ROW:    /* Fallthrough. */
        case CSS_FLEX_DIRECTION_ROW_REVERSE:
                return true;
        case CSS_FLEX_DIRECTION_COLUMN: /* Fallthrough. */
        case CSS_FLEX_DIRECTION_COLUMN_REVERSE:
                return false;
        }
}
 
static inline bool lh__flex_direction_reversed(const struct box *flex)
{
        switch (css_computed_flex_direction(flex->style)) {
        default:                             /* Fallthrough. */
        case CSS_FLEX_DIRECTION_ROW_REVERSE: /* Fallthrough. */
        case CSS_FLEX_DIRECTION_COLUMN_REVERSE:
                return true;
        case CSS_FLEX_DIRECTION_ROW: /* Fallthrough. */
        case CSS_FLEX_DIRECTION_COLUMN:
                return false;
        }
}
 
static inline int lh__non_auto_margin(const struct box *b, enum box_side side)
{
        return (b->margin[side] == AUTO) ? 0 : b->margin[side];
}
 
static inline int lh__delta_outer_height(const struct box *b)
{
        return b->padding[TOP] +
               b->padding[BOTTOM] +
               b->border[TOP].width +
               b->border[BOTTOM].width +
               lh__non_auto_margin(b, TOP) +
               lh__non_auto_margin(b, BOTTOM);
}
 
static inline int lh__delta_outer_width(const struct box *b)
{
        return b->padding[LEFT] +
               b->padding[RIGHT] +
               b->border[LEFT].width +
               b->border[RIGHT].width +
               lh__non_auto_margin(b, LEFT) +
               lh__non_auto_margin(b, RIGHT);
}
 
static inline int lh__delta_outer_main(
                const struct box *flex,
                const struct box *b)
{
        if (lh__flex_main_is_horizontal(flex)) {
                return lh__delta_outer_width(b);
        } else {
                return lh__delta_outer_height(b);
        }
}
 
static inline int lh__delta_outer_cross(
                const struct box *flex,
                const struct box *b)
{
        if (lh__flex_main_is_horizontal(flex) == false) {
                return lh__delta_outer_width(b);
        } else {
                return lh__delta_outer_height(b);
        }
}
 
static inline int *lh__box_size_main_ptr(
                bool horizontal,
                struct box *b)
{
        return horizontal ? &b->width : &b->height;
}
 
static inline int *lh__box_size_cross_ptr(
                bool horizontal,
                struct box *b)
{
        return horizontal ? &b->height : &b->width;
}
 
static inline int lh__box_size_main(
                bool horizontal,
                const struct box *b)
{
        return horizontal ? b->width : b->height;
}
 
static inline int lh__box_size_cross(
                bool horizontal,
                const struct box *b)
{
        return horizontal ? b->height : b->width;
}
 
static inline bool lh__box_size_cross_is_auto(
                bool horizontal,
                struct box *b)
{
        css_fixed length;
        css_unit unit;
 
        if (horizontal) {
                return css_computed_height(b->style,
                                &length, &unit) == CSS_HEIGHT_AUTO;
        } else {
                return css_computed_width(b->style,
                                &length, &unit) == CSS_WIDTH_AUTO;
        }
}
 
static inline enum css_align_self_e lh__box_align_self(
                const struct box *flex,
                const struct box *item)
{
        enum css_align_self_e align_self = css_computed_align_self(item->style);
 
        if (align_self == CSS_ALIGN_SELF_AUTO) {
                align_self = css_computed_align_items(flex->style);
        }
 
        return align_self;
}
 
/**
 * Determine width of margin, borders, and padding on one side of a box.
 *
 * \param unit_len_ctx  CSS length conversion context for document
 * \param style    style to measure
 * \param side     side of box to measure
 * \param margin   whether margin width is required
 * \param border   whether border width is required
 * \param padding  whether padding width is required
 * \param fixed    increased by sum of fixed margin, border, and padding
 * \param frac     increased by sum of fractional margin and padding
 */
static inline void calculate_mbp_width(
                const css_unit_ctx *unit_len_ctx,
                const css_computed_style *style,
                unsigned int side,
                bool margin,
                bool border,
                bool padding,
                int *fixed,
                float *frac)
{
        css_fixed value = 0;
        css_unit unit = CSS_UNIT_PX;
 
        assert(style);
 
        /* margin */
        if (margin) {
                enum css_margin_e type;
 
                type = margin_funcs[side](style, &value, &unit);
                if (type == CSS_MARGIN_SET) {
                        if (unit == CSS_UNIT_PCT) {
                                *frac += FIXTOFLT(FDIV(value, F_100));
                        } else {
                                *fixed += FIXTOINT(css_unit_len2device_px(
                                                style, unit_len_ctx,
                                                value, unit));
                        }
                }
        }
 
        /* border */
        if (border) {
                if (lh__have_border(side, style)) {
                        border_width_funcs[side](style, &value, &unit);
 
                        *fixed += FIXTOINT(css_unit_len2device_px(
                                        style, unit_len_ctx,
                                        value, unit));
                }
        }
 
        /* padding */
        if (padding) {
                padding_funcs[side](style, &value, &unit);
                if (unit == CSS_UNIT_PCT) {
                        *frac += FIXTOFLT(FDIV(value, F_100));
                } else {
                        *fixed += FIXTOINT(css_unit_len2device_px(
                                        style, unit_len_ctx,
                                        value, unit));
                }
        }
}
 
/**
 * Adjust a specified width or height for the box-sizing property.
 *
 * This turns the specified dimension into a content-box dimension.
 *
 * \param  unit_len_ctx          Length conversion context
 * \param  box              gadget to adjust dimensions of
 * \param  available_width  width of containing block
 * \param  setwidth         set true if the dimension to be tweaked is a width,
 *                              else set false for a height
 * \param  dimension        current value for given width/height dimension.
 *                              updated to new value after consideration of
 *                              gadget properties.
 */
static inline void layout_handle_box_sizing(
                const css_unit_ctx *unit_len_ctx,
                const struct box *box,
                int available_width,
                bool setwidth,
                int *dimension)
{
        enum css_box_sizing_e bs;
 
        assert(box && box->style);
 
        bs = css_computed_box_sizing(box->style);
 
        if (bs == CSS_BOX_SIZING_BORDER_BOX) {
                int orig = *dimension;
                int fixed = 0;
                float frac = 0;
 
                calculate_mbp_width(unit_len_ctx, box->style,
                                setwidth ? LEFT : TOP,
                                false, true, true, &fixed, &frac);
                calculate_mbp_width(unit_len_ctx, box->style,
                                setwidth ? RIGHT : BOTTOM,
                                false, true, true, &fixed, &frac);
                orig -= frac * available_width + fixed;
                *dimension = orig > 0 ? orig : 0;
        }
}
 
/**
 * Calculate width, height, and thickness of margins, paddings, and borders.
 *
 * \param  unit_len_ctx     Length conversion context
 * \param  available_width  width of containing block
 * \param  viewport_height  height of viewport in pixels or -ve if unknown
 * \param  box              current box
 * \param  style            style giving width, height, margins, paddings,
 *                          and borders
 * \param  width            updated to width, may be NULL
 * \param  height           updated to height, may be NULL
 * \param  max_width        updated to max-width, may be NULL
 * \param  min_width        updated to min-width, may be NULL
 * \param  max_height       updated to max-height, may be NULL
 * \param  min_height       updated to min-height, may be NULL
 * \param  margin           filled with margins, may be NULL
 * \param  padding          filled with paddings, may be NULL
 * \param  border           filled with border widths, may be NULL
 */
static inline void layout_find_dimensions(
                const css_unit_ctx *unit_len_ctx,
                int available_width,
                int viewport_height,
                const struct box *box,
                const css_computed_style *style,
                int *width,
                int *height,
                int *max_width,
                int *min_width,
                int *max_height,
                int *min_height,
                int margin[4],
                int padding[4],
                struct box_border border[4])
{
        struct box *containing_block = NULL;
        unsigned int i;
 
        if (width) {
                enum css_width_e wtype;
                css_fixed value = 0;
                css_unit unit = CSS_UNIT_PX;
 
                wtype = css_computed_width(style, &value, &unit);
 
                if (wtype == CSS_WIDTH_SET) {
                        if (unit == CSS_UNIT_PCT) {
                                *width = FPCT_OF_INT_TOINT(
                                                value, available_width);
                        } else {
                                *width = FIXTOINT(css_unit_len2device_px(
                                                style, unit_len_ctx,
                                                value, unit));
                        }
                } else {
                        *width = AUTO;
                }
 
                if (*width != AUTO) {
                        layout_handle_box_sizing(unit_len_ctx, box,
                                        available_width, true, width);
                }
        }
 
        if (height) {
                enum css_height_e htype;
                css_fixed value = 0;
                css_unit unit = CSS_UNIT_PX;
 
                htype = css_computed_height(style, &value, &unit);
 
                if (htype == CSS_HEIGHT_SET) {
                        if (unit == CSS_UNIT_PCT) {
                                enum css_height_e cbhtype;
 
                                if (css_computed_position(box->style) ==
                                                CSS_POSITION_ABSOLUTE &&
                                                box->parent) {
                                        /* Box is absolutely positioned */
                                        assert(box->float_container);
                                        containing_block = box->float_container;
                                } else if (box->float_container &&
                                        css_computed_position(box->style) !=
                                                CSS_POSITION_ABSOLUTE &&
                                        (css_computed_float(box->style) ==
                                                CSS_FLOAT_LEFT ||
                                         css_computed_float(box->style) ==
                                                CSS_FLOAT_RIGHT)) {
                                        /* Box is a float */
                                        assert(box->parent &&
                                                box->parent->parent &&
                                                box->parent->parent->parent);
 
                                        containing_block =
                                                box->parent->parent->parent;
                                } else if (box->parent && box->parent->type !=
                                                BOX_INLINE_CONTAINER) {
                                        /* Box is a block level element */
                                        containing_block = box->parent;
                                } else if (box->parent && box->parent->type ==
                                                BOX_INLINE_CONTAINER) {
                                        /* Box is an inline block */
                                        assert(box->parent->parent);
                                        containing_block = box->parent->parent;
                                }
 
                                if (containing_block) {
                                        css_fixed f = 0;
                                        css_unit u = CSS_UNIT_PX;
 
                                        cbhtype = css_computed_height(
                                                        containing_block->style,
                                                        &f, &u);
                                }
 
                                if (containing_block &&
                                        containing_block->height != AUTO &&
                                        (css_computed_position(box->style) ==
                                                        CSS_POSITION_ABSOLUTE ||
                                                cbhtype == CSS_HEIGHT_SET)) {
                                        /* Box is absolutely positioned or its
                                         * containing block has a valid
                                         * specified height.
                                         * (CSS 2.1 Section 10.5) */
                                        *height = FPCT_OF_INT_TOINT(value,
                                                containing_block->height);
                                } else if ((!box->parent ||
                                                !box->parent->parent) &&
                                                viewport_height >= 0) {
                                        /* If root element or it's child
                                         * (HTML or BODY) */
                                        *height = FPCT_OF_INT_TOINT(value,
                                                        viewport_height);
                                } else {
                                        /* precentage height not permissible
                                         * treat height as auto */
                                        *height = AUTO;
                                }
                        } else {
                                *height = FIXTOINT(css_unit_len2device_px(
                                                style, unit_len_ctx,
                                                value, unit));
                        }
                } else {
                        *height = AUTO;
                }
 
                if (*height != AUTO) {
                        layout_handle_box_sizing(unit_len_ctx, box,
                                        available_width, false, height);
                }
        }
 
        if (max_width) {
                enum css_max_width_e type;
                css_fixed value = 0;
                css_unit unit = CSS_UNIT_PX;
 
                type = css_computed_max_width(style, &value, &unit);
 
                if (type == CSS_MAX_WIDTH_SET) {
                        if (unit == CSS_UNIT_PCT) {
                                *max_width = FPCT_OF_INT_TOINT(value,
                                                available_width);
                        } else {
                                *max_width = FIXTOINT(css_unit_len2device_px(
                                                style, unit_len_ctx,
                                                value, unit));
                        }
                } else {
                        /* Inadmissible */
                        *max_width = -1;
                }
 
                if (*max_width != -1) {
                        layout_handle_box_sizing(unit_len_ctx, box,
                                        available_width, true, max_width);
                }
        }
 
        if (min_width) {
                enum css_min_width_e type;
                css_fixed value = 0;
                css_unit unit = CSS_UNIT_PX;
 
                type = ns_computed_min_width(style, &value, &unit);
 
                if (type == CSS_MIN_WIDTH_SET) {
                        if (unit == CSS_UNIT_PCT) {
                                *min_width = FPCT_OF_INT_TOINT(value,
                                                available_width);
                        } else {
                                *min_width = FIXTOINT(css_unit_len2device_px(
                                                style, unit_len_ctx,
                                                value, unit));
                        }
                } else {
                        /* Inadmissible */
                        *min_width = 0;
                }
 
                if (*min_width != 0) {
                        layout_handle_box_sizing(unit_len_ctx, box,
                                        available_width, true, min_width);
                }
        }
 
        if (max_height) {
                enum css_max_height_e type;
                css_fixed value = 0;
                css_unit unit = CSS_UNIT_PX;
 
                type = css_computed_max_height(style, &value, &unit);
 
                if (type == CSS_MAX_HEIGHT_SET) {
                        if (unit == CSS_UNIT_PCT) {
                                /* TODO: handle percentage */
                                *max_height = -1;
                        } else {
                                *max_height = FIXTOINT(css_unit_len2device_px(
                                                style, unit_len_ctx,
                                                value, unit));
                        }
                } else {
                        /* Inadmissible */
                        *max_height = -1;
                }
        }
 
        if (min_height) {
                enum css_min_height_e type;
                css_fixed value = 0;
                css_unit unit = CSS_UNIT_PX;
 
                type = ns_computed_min_height(style, &value, &unit);
 
                if (type == CSS_MIN_HEIGHT_SET) {
                        if (unit == CSS_UNIT_PCT) {
                                /* TODO: handle percentage */
                                *min_height = 0;
                        } else {
                                *min_height = FIXTOINT(css_unit_len2device_px(
                                                style, unit_len_ctx,
                                                value, unit));
                        }
                } else {
                        /* Inadmissible */
                        *min_height = 0;
                }
        }
 
        for (i = 0; i != 4; i++) {
                if (margin) {
                        enum css_margin_e type = CSS_MARGIN_AUTO;
                        css_fixed value = 0;
                        css_unit unit = CSS_UNIT_PX;
 
                        type = margin_funcs[i](style, &value, &unit);
 
                        if (type == CSS_MARGIN_SET) {
                                if (unit == CSS_UNIT_PCT) {
                                        margin[i] = FPCT_OF_INT_TOINT(value,
                                                        available_width);
                                } else {
                                        margin[i] = FIXTOINT(css_unit_len2device_px(
                                                        style, unit_len_ctx,
                                                        value, unit));
                                }
                        } else {
                                margin[i] = AUTO;
                        }
                }
 
                if (padding) {
                        css_fixed value = 0;
                        css_unit unit = CSS_UNIT_PX;
 
                        padding_funcs[i](style, &value, &unit);
 
                        if (unit == CSS_UNIT_PCT) {
                                padding[i] = FPCT_OF_INT_TOINT(value,
                                                available_width);
                        } else {
                                padding[i] = FIXTOINT(css_unit_len2device_px(
                                                style, unit_len_ctx,
                                                value, unit));
                        }
                }
 
                /* Table cell borders are populated in table.c */
                if (border && box->type != BOX_TABLE_CELL) {
                        enum css_border_style_e bstyle = CSS_BORDER_STYLE_NONE;
                        css_color color = 0;
                        css_fixed value = 0;
                        css_unit unit = CSS_UNIT_PX;
 
                        border_width_funcs[i](style, &value, &unit);
                        bstyle = border_style_funcs[i](style);
                        border_color_funcs[i](style, &color);
 
                        border[i].style = bstyle;
                        border[i].c = color;
 
                        if (bstyle == CSS_BORDER_STYLE_HIDDEN ||
                                        bstyle == CSS_BORDER_STYLE_NONE)
                                /* spec unclear: following Mozilla */
                                border[i].width = 0;
                        else
                                border[i].width = FIXTOINT(css_unit_len2device_px(
                                                style, unit_len_ctx,
                                                value, unit));
 
                        /* Special case for border-collapse: make all borders
                         * on table/table-row-group/table-row zero width. */
                        if (css_computed_border_collapse(style) ==
                                        CSS_BORDER_COLLAPSE_COLLAPSE &&
                                        (box->type == BOX_TABLE ||
                                         box->type == BOX_TABLE_ROW_GROUP ||
                                         box->type == BOX_TABLE_ROW))
                                border[i].width = 0;
                }
        }
}
 
#endif