GuiShape.cpp

/****************************************************************************
 * libgui
 * Daryl Borth 2026
 * GuiShape.cpp
 ***************************************************************************/
 
#include "Gui.h"
 
// A change of state blends through this many looks. Each is a mesh the cache can share between
// every shape making the same change, so only the first one to fade pays to build them.
static const int kBlendSteps = 4;
 
GuiShape::GuiShape(int w, int h) :
    kind(SHAPE::RECTANGLE), corners(0.0f), transition(0.12f),
    blend(1.0f), blendStep(kBlendSteps), started(false), dirty(true), meshWidth(-1), meshHeight(-1), meshFeather(-1.0f),
    mesh(nullptr)
{
    width = w;
    height = h;
}
 
GuiShape::~GuiShape()
{
    GuiMeshCache::release(mesh);
    mesh = nullptr;
}
 
void GuiShape::setShape(SHAPE s)
{
    kind = s;
    dirty = true;
}
 
void GuiShape::setCorners(const GuiCorners& c)
{
    corners = c;
    dirty = true;
}
 
void GuiShape::setCapsule()
{
    setCorners(GuiCorners(100000.0f)); // clamped to half the shorter side
}
 
void GuiShape::setStyle(const GuiShapeStyle& s)
{
    style = s;
    started = false; // draw the new look at once, without fading from the old one
}
 
void GuiShape::setPaint(const GuiPaint& p)
{
    setStyle(GuiShapeStyle(p));
}
 
void GuiShape::setTransition(float seconds)
{
    transition = seconds < 0.0f ? 0.0f : seconds;
}
 
static SHAPE_STATE shapeStateFor(STATE s)
{
    switch(s)
    {
        case STATE::SELECTED:
        case STATE::HELD:     return SHAPE_STATE::FOCUSED;
        case STATE::CLICKED:  return SHAPE_STATE::PRESSED;
        case STATE::DISABLED: return SHAPE_STATE::DISABLED;
        default:              return SHAPE_STATE::NORMAL;
    }
}
 
void GuiShape::draw()
{
    if(!this->isVisible())
        return;
 
    const int a = this->getAlpha();
    if(a > 0 && width > 0 && height > 0)
    {
        VideoDriver * video = platform->getVideo();
 
        // choose the paint for the current state, blending toward it when it changes
        const GuiPaint& want = style.forState(shapeStateFor(state));
        if(!started)
        {
            from = to = shown = want;
            blend = 1.0f;
            blendStep = kBlendSteps;
            started = true;
            dirty = true;
        }
        else if(want != to)
        {
            from = shown;
            to = want;
            blend = transition > 0.0f ? 0.0f : 1.0f;
            blendStep = 0;
            if(blend >= 1.0f)
            {
                shown = to;
                blendStep = kBlendSteps;
                dirty = true;
            }
        }
        if(blend < 1.0f)
        {
            blend += video->getDeltaTime() / transition;
            if(blend >= 1.0f)
            {
                blend = 1.0f;
                blendStep = kBlendSteps;
                shown = to;
                dirty = true;
            }
            else
            {
                // Look only changes a few times per blend, so the in-between meshes can be shared
                const float eased = blend * blend * (3.0f - 2.0f * blend);
                const int step = (int)(eased * (float)kBlendSteps + 0.5f);
                if(step != blendStep)
                {
                    blendStep = step;
                    shown = GuiPaint::mix(from, to, (float)step / (float)kBlendSteps);
                    dirty = true;
                }
            }
        }
 
        // look the geometry up again when anything it depends on changed
        const float scale = video->getUIScale();
        const float feather = scale > 0.0f ? 1.0f / scale : 1.0f;
        if(dirty || !mesh || meshWidth != width || meshHeight != height || meshFeather != feather)
        {
            GuiMeshKey key;
            key.kind = kind;
            key.width = width;
            key.height = height;
            key.corners = corners;
            key.paint = shown;
            key.feather = feather;
            key.tolerance = 0.3f * feather; // 0.3 of a physical pixel
            GuiSharedMesh * next = GuiMeshCache::acquire(key); // before releasing, in case it is the same mesh
            GuiMeshCache::release(mesh);
            mesh = next;
            meshWidth = width;
            meshHeight = height;
            meshFeather = feather;
            dirty = false;
        }
 
        // place it like an image: scaled about its own center, at the element's position
        const float sx = this->getScaleX();
        const float sy = this->getScaleY();
        const float hw = width * 0.5f;
        const float hh = height * 0.5f;
        GuiMeshCache::draw(mesh, this->getLeft() + hw - hw * sx, this->getTop() + hh - hh * sy, sx, sy, (uint8_t)a, scratch);
    }
 
    this->updateEffects();
}