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#pragma once
#include "LayoutRenderObject.h"
namespace cru::ui::render {
enum class FlexDirection {
Horizontal,
HorizontalReverse,
Vertical,
VertivalReverse
};
using FlexMainAlignment = Alignment;
using FlexCrossAlignment = Alignment;
struct FlexChildLayoutData {
float expand_factor = 0;
float shrink_factor = 1;
// nullopt stands for looking at parent's setting
std::optional<FlexCrossAlignment> cross_alignment = std::nullopt;
};
// Measure Logic (v0.1):
// Cross axis measure logic is the same as stack layout.
//
// 1. Layout all children with unspecified(infinate) max main axis length.
//
// 2. Add up main axis length of children to get total main length.
//
// 2.1. If preferred main axis length of parent is specified, then compare
// total length with it. If bigger, shrink is performed. If smaller, expand is
// performed. And preferred main axis length is used as target length.
//
// 2.2. If preferred main axis length of parent is not specified.
//
// 2.2.1. If max main axis length is specified and total length is bigger
// than max main axis length, shrink is performed and max main axis length is
// used as target length.
//
// 2.2.2. Or if max main axis length is specified and total length is smaller
// than max main axis length and any child has a positive expand factor, then
// expand is performed and max main axis length is used as target length.
//
// 2.2.3. Or if min main axis length is specified and total length is smaller
// than min main axis length, expand is performed and min main axis length is
// used as target length.
//
// 3. If shrink or expand is needed, then
//
// 3.1. Shrink:
//
// 3.1.1. Find out all shrink_factor > 0 children to form a adjusting list.
//
// 3.1.2. Use total main length minus target length to get the total shrink
// length. Add up all shrink_factor in adjusting list to get total shrink
// factor.
//
// 3.1.3. Iterate all children in adjusting list:
//
// 3.1.3.1. Calculate its own shrink length as
// shrink_factor / total_shrink_factor * total_shrink_length .
// Use current main axis length of child minus shrink length to get new
// measure length.
//
// 3.1.3.2. If min main axis length of the child is specified and new
// measure length is less than it, then min main axis length is used as new
// measure length.
//
// 3.1.3.3. Or if new measure length is less than 0, then it is coerced to
// 0.
//
// 3.1.3.4. Call measure with max and preferred main axis length set to new
// measure length. Cross axis length requirement is the same as step 1.
//
// 3.1.3.5. After measure, if it has min main axis length specified and
// actual main axis length is equal to it or its actual main axis length is
// 0, then remove it from adjusting list.
//
// 3.1.4. Add up main axis length of children to update total main length. If
// total main length is less than or equal to target length, goto step 4.
//
// 3.1.4. If adjusting list is not empty, go to step 3.1.2.
//
// 3.2. Expand:
// The same as shrink after you exchange related things except some minor
// things like do not do special things on 0.
//
// 4. If final total main axis length exceeeds the max main axis length (if
// specified), then report an error. And result main axis length is the coerced
// length. If final total main axis length is smaller than min main axis length
// (if specified), then coerce the length to the min value but not report error
// and just fill the rest space with blank.
//
class CRU_UI_API FlexLayoutRenderObject
: public LayoutRenderObject<FlexChildLayoutData> {
CRU_DEFINE_CLASS_LOG_TAG("FlexLayoutRenderObject")
public:
FlexLayoutRenderObject() = default;
FlexLayoutRenderObject(const FlexLayoutRenderObject& other) = delete;
FlexLayoutRenderObject& operator=(const FlexLayoutRenderObject& other) =
delete;
FlexLayoutRenderObject(FlexLayoutRenderObject&& other) = delete;
FlexLayoutRenderObject& operator=(FlexLayoutRenderObject&& other) = delete;
~FlexLayoutRenderObject() override = default;
String GetName() const override;
FlexDirection GetFlexDirection() const { return direction_; }
void SetFlexDirection(FlexDirection direction) {
direction_ = direction;
InvalidateLayout();
}
FlexMainAlignment GetContentMainAlign() const { return content_main_align_; }
void SetContentMainAlign(FlexMainAlignment align) {
content_main_align_ = align;
InvalidateLayout();
}
FlexCrossAlignment GetItemCrossAlign() const { return item_cross_align_; }
void SetItemCrossAlign(FlexCrossAlignment align) {
item_cross_align_ = align;
InvalidateLayout();
}
protected:
Size OnMeasureContent(const MeasureRequirement& requirement,
const MeasureSize& preferred_size) override;
void OnLayoutContent(const Rect& content_rect) override;
private:
FlexDirection direction_ = FlexDirection::Horizontal;
FlexMainAlignment content_main_align_ = FlexMainAlignment::Start;
FlexCrossAlignment item_cross_align_ = FlexCrossAlignment::Center;
};
} // namespace cru::ui::render
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