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Diffstat (limited to 'include/cru/ui/render/FlexLayoutRenderObject.h')
| -rw-r--r-- | include/cru/ui/render/FlexLayoutRenderObject.h | 120 |
1 files changed, 120 insertions, 0 deletions
diff --git a/include/cru/ui/render/FlexLayoutRenderObject.h b/include/cru/ui/render/FlexLayoutRenderObject.h new file mode 100644 index 00000000..3a8348f6 --- /dev/null +++ b/include/cru/ui/render/FlexLayoutRenderObject.h @@ -0,0 +1,120 @@ +#pragma once +#include "LayoutRenderObject.h" + +#include <string_view> + +namespace cru::ui::render { +// 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(u"cru::ui::render::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; + + std::u16string_view 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 |