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select: computed: Relative position fixes #33

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Merged
tlsa merged 1 commit into from
Jul 26, 2026
Merged

select: computed: Relative position fixes #33

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108 changes: 70 additions & 38 deletions src/select/computed.c
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Original file line number Diff line number Diff line change
Expand Up @@ -473,21 +473,30 @@ uint8_t css_computed_top(const css_computed_style *style,
if (position == CSS_POSITION_STATIC) {
/* Static -> auto */
top = CSS_TOP_AUTO;

} else if (position == CSS_POSITION_RELATIVE) {
/* Relative -> follow $9.4.3 */
uint8_t bottom = get_bottom_bits(style);

if (top == CSS_TOP_AUTO && (bottom & 0x3) == CSS_BOTTOM_AUTO) {
/* Both auto => 0px */
*length = 0;
*unit = CSS_UNIT_PX;
} else if (top == CSS_TOP_AUTO) {
/* Top is auto => -bottom */
*length = -style->i.bottom;
*unit = (css_unit) (bottom >> 2);
}
if (top == CSS_TOP_AUTO) {
css_fixed bottom_length;
css_unit bottom_unit;

uint8_t bottom = get_bottom(style,
&bottom_length,
&bottom_unit);

if (bottom == CSS_BOTTOM_SET) {
/* Top is auto, bottom is set, use `-bottom`. */
*length = -bottom_length;
*unit = bottom_unit;
} else {
/* Both auto => 0px */
*length = 0;
*unit = CSS_UNIT_PX;
}

top = CSS_TOP_SET;
top = CSS_TOP_SET;
}
}

return top;
Expand All @@ -503,18 +512,26 @@ uint8_t css_computed_right(const css_computed_style *style,
if (position == CSS_POSITION_STATIC) {
/* Static -> auto */
right = CSS_RIGHT_AUTO;

} else if (position == CSS_POSITION_RELATIVE) {
/* Relative -> follow $9.4.3 */
uint8_t left = get_left_bits(style);

if (right == CSS_RIGHT_AUTO && (left & 0x3) == CSS_LEFT_AUTO) {
/* Both auto => 0px */
*length = 0;
*unit = CSS_UNIT_PX;
} else if (right == CSS_RIGHT_AUTO) {
/* Right is auto => -left */
*length = -style->i.left;
*unit = (css_unit) (left >> 2);
css_fixed left_length;
css_unit left_unit;

uint8_t left = get_left(style,
&left_length,
&left_unit);

if (right == CSS_RIGHT_AUTO) {
if (left == CSS_LEFT_SET) {
/* Right is auto => -left */
*length = -left_length;
*unit = left_unit;
} else {
/* Both auto => 0px */
*length = 0;
*unit = CSS_UNIT_PX;
}
} else {
/** \todo Consider containing block's direction
* if overconstrained */
Expand All @@ -536,19 +553,26 @@ uint8_t css_computed_bottom(const css_computed_style *style,
if (position == CSS_POSITION_STATIC) {
/* Static -> auto */
bottom = CSS_BOTTOM_AUTO;

} else if (position == CSS_POSITION_RELATIVE) {
/* Relative -> follow $9.4.3 */
uint8_t top = get_top_bits(style);
css_fixed top_length;
css_unit top_unit;

if (bottom == CSS_BOTTOM_AUTO && (top & 0x3) == CSS_TOP_AUTO) {
/* Have to get top; if set at all, it overrides bottom */
uint8_t top = get_top(style,
&top_length,
&top_unit);

if (top == CSS_TOP_SET) {
/* Top is set; bottom doesn't matter => -top */
*length = -top_length;
*unit = top_unit;

} else if (bottom == CSS_BOTTOM_AUTO) {
/* Both auto => 0px */
*length = 0;
*unit = CSS_UNIT_PX;
} else if (bottom == CSS_BOTTOM_AUTO ||
(top & 0x3) != CSS_TOP_AUTO) {
/* Bottom is auto or top is not auto => -top */
*length = -style->i.top;
*unit = (css_unit) (top >> 2);
}

bottom = CSS_BOTTOM_SET;
Expand All @@ -567,18 +591,26 @@ uint8_t css_computed_left(const css_computed_style *style,
if (position == CSS_POSITION_STATIC) {
/* Static -> auto */
left = CSS_LEFT_AUTO;

} else if (position == CSS_POSITION_RELATIVE) {
/* Relative -> follow $9.4.3 */
uint8_t right = get_right_bits(style);

if (left == CSS_LEFT_AUTO && (right & 0x3) == CSS_RIGHT_AUTO) {
/* Both auto => 0px */
*length = 0;
*unit = CSS_UNIT_PX;
} else if (left == CSS_LEFT_AUTO) {
/* Left is auto => -right */
*length = -style->i.right;
*unit = (css_unit) (right >> 2);
css_fixed right_length;
css_unit right_unit;

uint8_t right = get_right(style,
&right_length,
&right_unit);

if (left == CSS_LEFT_AUTO) {
if (right == CSS_RIGHT_SET) {
/* Left is auto => -right */
*length = -right_length;
*unit = right_unit;
} else {
/* Both auto => 0px */
*length = 0;
*unit = CSS_UNIT_PX;
}
} else {
/** \todo Consider containing block's direction
* if overconstrained */
Expand Down
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