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LibWeb: Resolve auto margins on abspos elements in more cases

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Specifically, we now handle cases where all three of `left`, `width`
and `right` are non-`auto`.
This commit is contained in:
Andreas Kling 2023-06-13 16:25:11 +02:00
parent f7dc2742a9
commit 41da9a4231
3 changed files with 64 additions and 10 deletions
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6
Tests/LibWeb/Layout/expected/block-and-inline/abspos-with-auto-margins-in-inline-axis.txt Normal file
View file

@ -0,0 +1,6 @@
Viewport <#document> at (0,0) content-size 800x600 children: not-inline
BlockContainer <html> at (1,1) content-size 798x18 [BFC] children: not-inline
BlockContainer <body> at (10,10) content-size 780x0 children: not-inline
BlockContainer <div#foo> at (350,1) content-size 100x100 positioned [BFC] children: not-inline
BlockContainer <div#bar> at (699,101) content-size 100x100 positioned [BFC] children: not-inline
BlockContainer <div#baz> at (1,201) content-size 100x100 positioned [BFC] children: not-inline

31
Tests/LibWeb/Layout/input/block-and-inline/abspos-with-auto-margins-in-inline-axis.html Normal file
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@ -0,0 +1,31 @@
<!DOCTYPE html><style>
* {
border: 1px solid black;
}
div {
height: 100px;
width: 100px;
position: absolute;
height: 100px;
}
#foo {
margin: auto;
left: 0px;
right: 0px;
top: 0px;
}
#bar {
margin-left: auto;
margin-right: 0px;
left: 0px;
right: 0px;
top: 100px;
}
#baz {
margin-left: 0px;
margin-right: auto;
left: 0px;
right: 0px;
top: 200px;
}
</style><div id=foo></div><div id=bar></div><div id=baz></div>

37
Userland/Libraries/LibWeb/Layout/FormattingContext.cpp
View file

@ -598,8 +598,34 @@ void FormattingContext::compute_width_for_absolutely_positioned_non_replaced_ele
goto Rule3;
}
// If none of the three is auto:
if (!computed_left.is_auto() && !width.is_auto() && !computed_right.is_auto()) {
// FIXME: This should be solved in a more complicated way.
// If both margin-left and margin-right are auto,
// solve the equation under the extra constraint that the two margins get equal values
// FIXME: unless this would make them negative, in which case when direction of the containing block is ltr (rtl), set margin-left (margin-right) to 0 and solve for margin-right (margin-left).
auto size_available_for_margins = width_of_containing_block - border_left - padding_left - width.to_px(box) - padding_right - border_right - right;
if (margin_left.is_auto() && margin_right.is_auto()) {
margin_left = CSS::Length::make_px(size_available_for_margins / 2);
margin_right = CSS::Length::make_px(size_available_for_margins / 2);
return width;
}
// If one of margin-left or margin-right is auto, solve the equation for that value.
if (margin_left.is_auto()) {
margin_left = CSS::Length::make_px(size_available_for_margins);
return width;
}
if (margin_right.is_auto()) {
margin_right = CSS::Length::make_px(size_available_for_margins);
return width;
}
// If the values are over-constrained, ignore the value for left
// (in case the direction property of the containing block is rtl)
// or right (in case direction is ltr) and solve for that value.
// NOTE: At this point we *are* over-constrained since none of margin-left, left, width, right, or margin-right are auto.
// FIXME: Check direction.
right = solve_for_right();
return width;
}
@ -995,9 +1021,7 @@ void FormattingContext::layout_absolutely_positioned_element(Box const& box, Ava
compute_height_for_absolutely_positioned_element(box, available_space, BeforeOrAfterInsideLayout::After);
box_state.margin_left = box.computed_values().margin().left().to_px(box, width_of_containing_block);
box_state.margin_top = box.computed_values().margin().top().to_px(box, width_of_containing_block);
box_state.margin_right = box.computed_values().margin().right().to_px(box, width_of_containing_block);
box_state.margin_bottom = box.computed_values().margin().bottom().to_px(box, width_of_containing_block);
box_state.border_left = box.computed_values().border_left().width;
@ -1015,13 +1039,6 @@ void FormattingContext::layout_absolutely_positioned_element(Box const& box, Ava
box_state.inset_right = computed_right.to_px(box, width_of_containing_block);
box_state.inset_bottom = computed_bottom.to_px(box, height_of_containing_block);
if (computed_left.is_auto() && box.computed_values().width().is_auto() && computed_right.is_auto()) {
if (box.computed_values().margin().left().is_auto())
box_state.margin_left = 0;
if (box.computed_values().margin().right().is_auto())
box_state.margin_right = 0;
}
auto static_position = calculate_static_position(box);
CSSPixelPoint used_offset;