GuiLayout.cpp

/****************************************************************************
 * libgui
 * Daryl Borth 2026
 * GuiLayout.cpp
 ***************************************************************************/
 
#include "Gui.h"
#include <cmath>
 
static int roundi(float v)
{
    return (int)floorf(v + 0.5f);
}
 
GuiLayout::GuiLayout() :
    spacingX(0.0f), spacingY(0.0f), justify(LAYOUT_JUSTIFY::START), alignItems(LAYOUT_ALIGN::START),
    userFixedW(0), userFixedH(0), assignedW(0), assignedH(0), naturalW(0), naturalH(0), dirty(true), settled(false)
{
}
 
GuiLayout& GuiLayout::add(GuiElement* e, const GuiItem& item)
{
    if(!e)
        return *this;
 
    this->append(e); // calls remove(e) first, which drops any earlier entry for it
    Entry en;
    en.e = e;
    en.item = item;
    entries.push_back(en);
    dirty = true;
    return *this;
}
 
GuiLayout& GuiLayout::addGap(float size)
{
    Entry en;
    en.gapSize = size < 0.0f ? 0.0f : size;
    entries.push_back(en);
    dirty = true;
    return *this;
}
 
GuiLayout& GuiLayout::addSpace(float weight)
{
    Entry en;
    en.item.grow(weight);
    entries.push_back(en);
    dirty = true;
    return *this;
}
 
GuiLayout& GuiLayout::setPadding(float all)
{
    return setPadding(all, all, all, all);
}
 
GuiLayout& GuiLayout::setPadding(float horizontal, float vertical)
{
    return setPadding(horizontal, vertical, horizontal, vertical);
}
 
GuiLayout& GuiLayout::setPadding(float left, float top, float right, float bottom)
{
    padding = GuiInsets(left, top, right, bottom);
    dirty = true;
    return *this;
}
 
GuiLayout& GuiLayout::setSpacing(float s)
{
    return setSpacing(s, s);
}
 
GuiLayout& GuiLayout::setSpacing(float x, float y)
{
    spacingX = x;
    spacingY = y;
    dirty = true;
    return *this;
}
 
GuiLayout& GuiLayout::setJustify(LAYOUT_JUSTIFY j)
{
    justify = j;
    dirty = true;
    return *this;
}
 
GuiLayout& GuiLayout::setAlignItems(LAYOUT_ALIGN a)
{
    alignItems = a;
    dirty = true;
    return *this;
}
 
GuiLayout& GuiLayout::setFixedSize(int w, int h)
{
    userFixedW = w < 0 ? 0 : w;
    userFixedH = h < 0 ? 0 : h;
    dirty = true;
    return *this;
}
 
void GuiLayout::invalidate()
{
    dirty = true;
}
 
void GuiLayout::clear()
{
    this->removeAll();
    entries.clear();
    dirty = true;
}
 
void GuiLayout::remove(GuiElement* e)
{
    GuiWindow::remove(e);
    for(size_t i = 0; i < entries.size(); i++)
    {
        if(entries[i].e == e)
        {
            entries.erase(entries.begin() + i);
            break;
        }
    }
    dirty = true;
}
 
//Entries follow the window's children: pick up children added with append() directly,
//and drop entries whose child was removed some other way
void GuiLayout::syncEntries()
{
    // Nearly always the entries are exactly the children, in order (gaps aside): confirm that in one
    // pass and skip the searches below, which compare every entry with every child
    size_t next = 0;
    bool inSync = true;
    for(const Entry& en : entries)
    {
        if(!en.e)
            continue;
        if(next >= _elements.size() || _elements[next] != en.e)
        {
            inSync = false;
            break;
        }
        next++;
    }
    if(inSync && next == _elements.size())
        return;
 
    for(size_t i = 0; i < entries.size();)
    {
        if(entries[i].e && !this->find(entries[i].e))
            entries.erase(entries.begin() + i), dirty = true;
        else
            i++;
    }
    for(GuiElement* child : _elements)
    {
        bool known = false;
        for(const Entry& en : entries)
            if(en.e == child) { known = true; break; }
        if(!known)
        {
            Entry en;
            en.e = child;
            entries.push_back(en);
            dirty = true;
        }
    }
}
 
void GuiLayout::layout()
{
    settled = true;
 
    // nested layouts settle first, so their sizes are right when measured below
    for(Entry& en : entries)
        if(en.e)
            en.e->layout();
    this->syncEntries();
 
    std::vector<Entry*>& visible = visibleScratch;
    visible.clear();
    bool changed = dirty;
    for(Entry& en : entries)
    {
        const bool shown = !en.e || en.e->isVisible();
        if(shown != en.lastVisible)
        {
            changed = true;
            en.lastVisible = shown;
        }
        if(!shown)
            continue;
 
        if(en.e)
        {
            int w, h;
            en.e->getNaturalSize(w, h);
            if(en.haveAssigned && w == en.assignedW && h == en.assignedH)
            {
                // still the size layout gave it: its natural size is what it was before
                w = en.baseW;
                h = en.baseH;
            }
            else
            {
                en.baseW = w;
                en.baseH = h;
                en.haveAssigned = false;
            }
            if(w != en.lastW || h != en.lastH)
            {
                changed = true;
                en.lastW = w;
                en.lastH = h;
            }
            en.natW = w;
            en.natH = h;
        }
        visible.push_back(&en);
    }
    if(!changed)
        return;
    dirty = false;
 
    GuiLayoutResult fit = this->solve(visible, (float)userFixedW, (float)userFixedH);
    naturalW = roundi(fit.width);
    naturalH = roundi(fit.height);
 
    GuiLayoutResult res = fit;
    if(assignedW > 0 || assignedH > 0)
        res = this->solve(visible, (float)(assignedW > 0 ? assignedW : userFixedW), (float)(assignedH > 0 ? assignedH : userFixedH));
    width = roundi(res.width);
    height = roundi(res.height);
 
    for(size_t i = 0; i < visible.size() && i < res.rects.size(); i++)
    {
        Entry& en = *visible[i];
        if(!en.e)
            continue;
 
        const GuiRect& r = res.rects[i];
        const int w = roundi(r.w), h = roundi(r.h);
        if(w != en.natW || h != en.natH)
        {
            en.e->setLayoutSize(w, h);
            en.assignedW = w;
            en.assignedH = h;
            en.haveAssigned = true;
            en.e->layout(); // a nested layout re-flows to its new size right away
        }
        else if(en.haveAssigned)
        {
            en.e->setLayoutSize(en.baseW, en.baseH);
            en.haveAssigned = false;
            en.e->layout();
        }
        en.e->setLayoutPosition(roundi(r.x), roundi(r.y));
    }
}
 
// A layout inside another layout is settled by its parent's layout() on the way down, which comes
// just before the parent updates or draws it. Repeating that here would re-measure everything below
// it once more for every level of nesting.
void GuiLayout::draw()
{
    if(!settled)
        this->layout();
    GuiWindow::draw();
    settled = false;
}
 
void GuiLayout::update(InputController * c)
{
    if(!settled)
        this->layout();
    GuiWindow::update(c);
    settled = false;
}
 
void GuiLayout::getNaturalSize(int& w, int& h)
{
    w = naturalW;
    h = naturalH;
}
 
void GuiLayout::setLayoutSize(int w, int h)
{
    assignedW = w < 0 ? 0 : w;
    assignedH = h < 0 ? 0 : h;
    width = assignedW;
    height = assignedH;
    dirty = true;
}
 
void GuiLayout::collectNavigable(std::vector<GuiElement*>& out)
{
    for(GuiElement* child : _elements)
        child->collectNavigable(out);
}
 
GuiRow::GuiRow(int w, int h)
{
    setFixedSize(w, h);
}
 
GuiLayoutResult GuiRow::solve(const std::vector<Entry*>& visible, float fixedW, float fixedH)
{
    GuiStackSpec spec;
    spec.vertical = false;
    spec.padding = padding;
    spec.spacing = spacingX;
    spec.fixedW = fixedW;
    spec.fixedH = fixedH;
    spec.justify = justify;
    spec.alignItems = alignItems;
 
    std::vector<GuiStackItem> items(visible.size());
    for(size_t i = 0; i < visible.size(); i++)
    {
        const Entry& en = *visible[i];
        if(en.e) { items[i].w = (float)en.natW; items[i].h = (float)en.natH; }
        else items[i].w = en.gapSize;
        items[i].grow = en.item.growWeight;
        items[i].useContainerAlign = !en.item.hasAlignV;
        items[i].align = en.item.alignV;
    }
    return GuiSolveStack(spec, items);
}
 
GuiColumn::GuiColumn(int w, int h)
{
    setFixedSize(w, h);
}
 
GuiLayoutResult GuiColumn::solve(const std::vector<Entry*>& visible, float fixedW, float fixedH)
{
    GuiStackSpec spec;
    spec.vertical = true;
    spec.padding = padding;
    spec.spacing = spacingY;
    spec.fixedW = fixedW;
    spec.fixedH = fixedH;
    spec.justify = justify;
    spec.alignItems = alignItems;
 
    std::vector<GuiStackItem> items(visible.size());
    for(size_t i = 0; i < visible.size(); i++)
    {
        const Entry& en = *visible[i];
        if(en.e) { items[i].w = (float)en.natW; items[i].h = (float)en.natH; }
        else items[i].h = en.gapSize;
        items[i].grow = en.item.growWeight;
        items[i].useContainerAlign = !en.item.hasAlignH;
        items[i].align = en.item.alignH;
    }
    return GuiSolveStack(spec, items);
}
 
GuiGrid::GuiGrid(int cols, int w, int h) : columns(cols < 1 ? 1 : cols)
{
    setFixedSize(w, h);
}
 
GuiLayoutResult GuiGrid::solve(const std::vector<Entry*>& visible, float fixedW, float fixedH)
{
    GuiGridSpec spec;
    spec.columns = columns;
    spec.padding = padding;
    spec.spacingX = spacingX;
    spec.spacingY = spacingY;
    spec.fixedW = fixedW;
    spec.fixedH = fixedH;
 
    std::vector<GuiGridItem> items(visible.size());
    for(size_t i = 0; i < visible.size(); i++)
    {
        const Entry& en = *visible[i];
        if(en.e) { items[i].w = (float)en.natW; items[i].h = (float)en.natH; }
        else items[i].w = items[i].h = en.gapSize; // a gap holds a cell open
        if(en.item.hasAlignH) items[i].alignH = en.item.alignH;
        if(en.item.hasAlignV) items[i].alignV = en.item.alignV;
    }
    return GuiSolveGrid(spec, items);
}
 
GuiOverlay::GuiOverlay(int w, int h)
{
    setFixedSize(w, h);
}
 
GuiLayoutResult GuiOverlay::solve(const std::vector<Entry*>& visible, float fixedW, float fixedH)
{
    GuiOverlaySpec spec;
    spec.padding = padding;
    spec.fixedW = fixedW;
    spec.fixedH = fixedH;
 
    std::vector<GuiOverlayItem> items;
    for(size_t i = 0; i < visible.size(); i++)
    {
        const Entry& en = *visible[i];
        GuiOverlayItem it;
        it.w = (float)en.natW;
        it.h = (float)en.natH;
        it.background = en.item.isBackground;
        if(en.item.hasAlignH) it.alignH = en.item.alignH;
        if(en.item.hasAlignV) it.alignV = en.item.alignV;
        items.push_back(it);
    }
    return GuiSolveOverlay(spec, items);
}