Crafter.Graphics/interfaces/Crafter.Graphics-UIComponents.cppm

//SPDX-License-Identifier: LGPL-3.0-only
//SPDX-FileCopyrightText: Copyright (C) 2026 Catcrafts®

export module Crafter.Graphics:UIComponents;
import std;
import :UI;
import :Font;
import :FontAtlas;

// Tier 3: stateless presentation functions. These append items to the user's
// QuadItem / GlyphItem buffers — they do NOT dispatch. The user dispatches
// via UIRenderer::DispatchQuads / DispatchText after their onBuild fills
// everything, so a frame stays one quads dispatch + one text dispatch
// regardless of how many components were drawn.
//
// State for components that need it (hovered, pressed, dragging, t01) is the
// USER's responsibility — these functions are pure presentation.
//
// EXTENSION MODEL: each function below is short on purpose. If you want a
// hexagon button, an icon-with-label button, a tristate checkbox — copy the
// function body into your code and modify it. There is no override hook.

export namespace Crafter {
    // Aggregate for the standard item buffers + the optional text-shaping
    // deps. Build one per frame in onBuild and pass it to component calls.
    // Any pointer left null causes the corresponding component to be a no-op
    // (so a frame that doesn't draw images can leave `images` unset).
    struct UIBuffer {
        QuadItem*      quads      = nullptr;
        std::uint32_t* quadCount  = nullptr;
        std::uint32_t  quadCap    = 0;

        GlyphItem*     glyphs     = nullptr;
        std::uint32_t* glyphCount = nullptr;
        std::uint32_t  glyphCap   = 0;

        ImageItem*     images     = nullptr;
        std::uint32_t* imageCount = nullptr;
        std::uint32_t  imageCap   = 0;

        FontAtlas*     atlas      = nullptr;   // for text-emitting components
        UIRenderer*    renderer   = nullptr;   // for ShapeText
    };

    // ─── per-component color blocks ─────────────────────────────────────
    // Inline POD aggregates. Users compose their own application-level theme
    // by holding a few of these together; the library has no Theme type.

    struct ButtonColors {
        std::array<float, 4> bg;
        std::array<float, 4> bgHover;
        std::array<float, 4> bgPressed;
        std::array<float, 4> text;
        std::array<float, 4> border          = {0, 0, 0, 0};
        float                cornerRadius    = 0;
        float                borderThickness = 0;
    };

    struct CheckboxColors {
        std::array<float, 4> bg;
        std::array<float, 4> bgHover;
        std::array<float, 4> check;
        std::array<float, 4> border          = {0, 0, 0, 0};
        float                cornerRadius    = 4;
        float                borderThickness = 1;
        float                checkInset      = 4;     // px on each side
    };

    struct SliderColors {
        std::array<float, 4> track;
        std::array<float, 4> trackFilled;
        std::array<float, 4> thumb;
        std::array<float, 4> thumbHover;
        float                trackHeight     = 4;
        float                thumbRadius     = 8;
    };

    struct ProgressColors {
        std::array<float, 4> bg;
        std::array<float, 4> fill;
        float                cornerRadius    = 0;
    };

    // TextAlign lives in the :UI partition (used by UIRenderer::ShapeText).

    // ─── component functions ───────────────────────────────────────────

    // Background quad (color depends on state) + centered label glyphs.
    void DrawButton(UIBuffer& buf, Rect r, std::string_view label,
                    bool hovered, bool pressed,
                    Font& font, float fontSize,
                    const ButtonColors& c);

    // Outlined quad + a smaller filled inset quad when `checked`.
    void DrawCheckbox(UIBuffer& buf, Rect r, bool checked, bool hovered,
                      const CheckboxColors& c);

    // Thin track quad split at `t01` into filled/empty + a circular thumb
    // (drawn as a quad with cornerRadius = thumbRadius).
    void DrawSlider(UIBuffer& buf, Rect r, float t01, bool dragging,
                    const SliderColors& c);

    // Background quad + a filled quad clipped to t01 of the inner width.
    void DrawProgressBar(UIBuffer& buf, Rect r, float t01,
                         const ProgressColors& c);

    // Single-line text emit. `(x, baselineY)` is the start position; horizontal
    // alignment shifts the run after shaping. Returns the advance width that
    // was written. No line-wrap, no kerning — same shaping rules as
    // UIRenderer::ShapeText (which this calls).
    float DrawText(UIBuffer& buf, std::string_view text,
                   float x, float baselineY,
                   Font& font, float fontSize,
                   std::array<float, 4> color,
                   TextAlign align = TextAlign::Left);

    // Sampled image quad. The texture and sampler must already have heap
    // slots (UIRenderer::RegisterImage / RegisterSampler). `uv` is
    // {u0, v0, u1, v1} into the source texture; defaults to the full image.
    void DrawImage(UIBuffer& buf, Rect r,
                   std::uint32_t textureSlot, std::uint32_t samplerSlot,
                   std::array<float, 4> tint = {1, 1, 1, 1},
                   std::array<float, 4> uv   = {0, 0, 1, 1});
}