lintunes/lintunes/theme.py

"""App-wide theming: highlight color and UI/text scale, driven by Preferences.

Everything that shows the highlight color (table/sidebar selection, the seek
slider's filled groove, the visualizer bars) reads QPalette.Highlight, so
recoloring is a palette swap. UI scale adjusts the app font, scrollbar
dimensions, and (via MainWindow.apply_ui_metrics) table row heights.
"""
from PyQt6.QtGui import QPalette, QColor, QFontDatabase, QIcon, QPixmap


# The font the now-playing panel wants by default. Not bundled (it's a
# proprietary Monotype face), so it's simply the head of the fallback chain
# below: whatever geometric sans this machine actually has wins, silently.
# Startup never asks — the user can override in Edit ▸ Preferences.
CENTURY_GOTHIC = "Century Gothic"

# Closest-first substitutes for Century Gothic. URW Gothic is the ITC Avant
# Garde clone CG derives from and ships with ghostscript, so it's present on
# most Linux boxes; TeX Gyre Adventor is its TeX-world descendant. Names must
# be spelled exactly as the family is registered — QFontDatabase does no fuzzy
# matching, which is why "Jost*" appears with its asterisk.
NOW_PLAYING_FALLBACKS = (
    CENTURY_GOTHIC,
    "URW Gothic", "URW Gothic L", "URW Gothic Book",
    "TeX Gyre Adventor",
    "Questrial", "Didact Gothic", "Jost*", "Jost", "Josefin Sans",
    "Poppins", "Futura", "Avant Garde", "ITC Avant Garde Gothic",
    "Montserrat", "Nunito Sans", "Nunito",
)


HIGHLIGHT_COLORS = {
    "blue": "#3584E4",
    "marigold": "#F5A623",
    "magenta": "#D6409F",
    "seafoam": "#7FD1AE",
    "gray": "#8A8A8A",
}

UI_SCALES = {
    "small": {"font_pt": 9, "scrollbar": 10, "row_height": 20, "header_strip": 28,
              "status_height": 22},
    "medium": {"font_pt": 11, "scrollbar": 14, "row_height": 24, "header_strip": 34,
               "status_height": 26},
    "large": {"font_pt": 13, "scrollbar": 18, "row_height": 28, "header_strip": 40,
              "status_height": 32},
}

_base_palette = None


# The five user-tunable grayscale surfaces. now-playing bg/text have fixed
# defaults (white/black); the rest default to whatever the base palette uses,
# so an untouched install looks exactly as it did before the feature existed.
_PALETTE_GRAY_ROLE = {
    "color_background": QPalette.ColorRole.Window,
    "color_stripe": QPalette.ColorRole.AlternateBase,
    "color_button": QPalette.ColorRole.AlternateBase,
}
_FIXED_GRAY_DEFAULT = {
    "color_now_playing_bg": 255,
    "color_now_playing_text": 0,
}


def _base() -> QPalette:
    """The app's original palette, captured once, used as the reference for
    highlight/grayscale overrides and for the sliders' 'current' defaults."""
    global _base_palette
    if _base_palette is None:
        from PyQt6.QtWidgets import QApplication
        app = QApplication.instance()
        _base_palette = QPalette(app.palette()) if app is not None else QPalette()
    return _base_palette


def gray(value) -> QColor:
    """A 0..255 lightness as an opaque gray QColor."""
    v = max(0, min(255, int(value)))
    return QColor(v, v, v)


def default_gray(key: str) -> int:
    """The slider's value when this surface hasn't been overridden — i.e. its
    current appearance, so showing the slider doesn't imply a change."""
    if key in _FIXED_GRAY_DEFAULT:
        return _FIXED_GRAY_DEFAULT[key]
    if key == "color_visualizer_gray":
        # Dim-mode bars derive from alternateBase dropped ~12% in lightness
        # (see VisualizerWidget._bar_color); mirror that so the slider shows
        # the current appearance.
        color = _base().color(QPalette.ColorGroup.Active,
                              QPalette.ColorRole.AlternateBase)
        h, s, l, a = color.getHslF()
        color.setHslF(h, s, l * 0.88, a)
    else:
        color = _base().color(QPalette.ColorGroup.Active,
                              _PALETTE_GRAY_ROLE[key])
    return round(0.299 * color.red() + 0.587 * color.green()
                 + 0.114 * color.blue())


def gray_value(prefs, key: str) -> int:
    """The 0..255 value to show/apply for a surface: the saved override, or the
    current default when the user hasn't touched it."""
    saved = prefs.get(key)
    return default_gray(key) if saved is None else max(0, min(255, int(saved)))


def swatch_icon(color_hex: str, size: int = 18) -> QIcon:
    """A flat square of `color_hex` — the icon on a color-choosing control."""
    pixmap = QPixmap(size, size)
    pixmap.fill(QColor(color_hex))
    return QIcon(pixmap)


def highlight_palette(prefs) -> dict:
    """The highlight swatches as this user has them: the stock colors, with
    any slot they repainted (Preferences → a swatch → color picker) in its
    place. Saved in ``highlight_palette`` as {slot name: "#rrggbb"}."""
    palette = dict(HIGHLIGHT_COLORS)
    saved = prefs.get("highlight_palette") or {}
    if isinstance(saved, dict):
        for name, value in saved.items():
            if name in palette and QColor.isValidColorName(str(value)):
                palette[name] = QColor(str(value)).name()
    return palette


def highlight_color(prefs) -> QColor:
    palette = highlight_palette(prefs)
    return QColor(palette.get(prefs.get("highlight"), palette["blue"]))


def scale_metrics(prefs) -> dict:
    return UI_SCALES.get(prefs.get("ui_scale"), UI_SCALES["medium"])


def apply_theme(app, prefs):
    base = _base()

    color = highlight_color(prefs)
    # Black text on light highlights, white on dark
    luminance = (0.299 * color.red() + 0.587 * color.green()
                 + 0.114 * color.blue()) / 255
    text = QColor("black") if luminance > 0.6 else QColor("white")

    palette = QPalette(base)
    groups = (QPalette.ColorGroup.Active, QPalette.ColorGroup.Inactive)
    for group in groups:
        palette.setColor(group, QPalette.ColorRole.Highlight, color)
        palette.setColor(group, QPalette.ColorRole.HighlightedText, text)
        palette.setColor(group, QPalette.ColorRole.Accent, color)
    # User grayscale overrides (None = leave the base color untouched). The
    # button-box color lives in transport.py, not the palette.
    background = prefs.get("color_background")
    if background is not None:
        for group in groups:
            palette.setColor(group, QPalette.ColorRole.Window, gray(background))
    stripe = prefs.get("color_stripe")
    if stripe is not None:
        for group in groups:
            palette.setColor(group, QPalette.ColorRole.AlternateBase, gray(stripe))
    app.setPalette(palette)

    metrics = scale_metrics(prefs)
    font = app.font()
    font.setPointSize(metrics["font_pt"])
    app.setFont(font)

    bar = metrics["scrollbar"]
    button = palette.color(QPalette.ColorRole.Button)
    app.setStyleSheet(f"""
        QScrollBar:vertical {{ width: {bar}px; }}
        QScrollBar:horizontal {{ height: {bar}px; }}
        QScrollBar::handle {{ min-height: {bar * 2}px; min-width: {bar * 2}px; }}
        {button_emboss_qss(button)}
    """)


def emboss_stops(color: QColor, pressed: bool = False) -> list:
    """[(position, QColor)] of the emboss: a crisp lit rim along the top and
    a crisp shaded rim along the bottom, with the face itself nearly flat.
    ``pressed`` flips it — a button sinking in, or a debossed panel. The
    color itself sits at the midpoint, so what the user picked is still
    exactly what the middle shows."""
    rim_top, face_top = color.lighter(EMBOSS_RIM), color.lighter(EMBOSS_LIGHTER)
    face_bottom, rim_bottom = color.darker(EMBOSS_DARKER), color.darker(EMBOSS_RIM)
    if pressed:
        rim_top, face_top, face_bottom, rim_bottom = (
            rim_bottom, face_bottom, face_top, rim_top)
    return [(0, rim_top), (EMBOSS_RIM_WIDTH, face_top), (0.5, color),
            (round(1 - EMBOSS_RIM_WIDTH, 2), face_bottom), (1, rim_bottom)]


def emboss_gradient(color: QColor, pressed: bool = False) -> str:
    """``emboss_stops`` as a style-sheet gradient. Computed from the live
    color, so it follows the palette and the user's grayscale overrides."""
    stops = ", ".join(f"stop:{pos} {c.name()}"
                      for pos, c in emboss_stops(color, pressed))
    return f"qlineargradient(x1:0, y1:0, x2:0, y2:1, {stops})"


# How far the emboss strays from the base color (Qt's lighter/darker factor,
# 100 = unchanged). The face barely moves; the rims are where the shape is.
EMBOSS_LIGHTER = 103
EMBOSS_DARKER = 103
EMBOSS_RIM = 116
EMBOSS_RIM_WIDTH = 0.08     # fraction of the height each rim takes
HOVER_DARKER = 107          # hover: the whole button, slightly darker
PRESSED_DARKER = 112


def emboss_edges(color: QColor) -> str:
    """A defined outline: a touch darker at the bottom, like a lit shape."""
    edge = color.darker(135).name()
    bottom = color.darker(155).name()
    return f"border: 1px solid {edge}; border-bottom-color: {bottom};"


def deboss_edges(color: QColor) -> str:
    """The emboss outline turned over: darker along the top, as a panel set
    into the surface catches shadow there."""
    edge = color.darker(135).name()
    top = color.darker(155).name()
    return f"border: 1px solid {edge}; border-top-color: {top};"


def deboss_qss(selector: str, color: QColor, *, radius: int = 8,
               extra: str = "") -> str:
    """Pushed in, by exactly as much as a button is pushed out: the same
    rims and outline, flipped. For panels that show things rather than do
    things (the now-playing panel, the visualizer)."""
    return (f"{selector} {{ {deboss_edges(color)} border-radius: {radius}px;"
            f" background: {emboss_gradient(color, pressed=True)}; {extra} }}")


def paint_deboss(painter, rect, color: QColor, radius: float):
    """``deboss_qss`` for a widget that paints itself: fills ``rect`` (a
    QRectF) as a debossed rounded panel and returns its path, for clipping."""
    from PyQt6.QtCore import QPointF
    from PyQt6.QtGui import QLinearGradient, QPainterPath, QPen
    path = QPainterPath()
    path.addRoundedRect(rect, radius, radius)
    gradient = QLinearGradient(QPointF(0, rect.top()), QPointF(0, rect.bottom()))
    for pos, stop in emboss_stops(color, pressed=True):
        gradient.setColorAt(pos, stop)
    painter.fillPath(path, gradient)
    painter.setPen(QPen(color.darker(135), 1))
    painter.drawPath(path)
    # the darker top edge
    painter.save()
    painter.setClipRect(rect.adjusted(-1, -1, 1, -rect.height() / 2))
    painter.setPen(QPen(color.darker(155), 1))
    painter.drawPath(path)
    painter.restore()
    return path


def button_face_qss(selector: str, color: QColor, *, radius: int = 4,
                    extra: str = "", checked_color: QColor | None = None,
                    checked_text: str = "") -> str:
    """The one look every button shares: the emboss, the outline, a hover that
    darkens the whole button a little, and a pressed state that sinks in.
    ``extra`` carries per-button layout (padding, margins, corners);
    ``checked_color`` is for toggles like the Library button."""
    hover = color.darker(HOVER_DARKER)
    down = color.darker(PRESSED_DARKER)
    qss = (f"{selector} {{ {emboss_edges(color)} border-radius: {radius}px;"
           f" background: {emboss_gradient(color)}; {extra} }}"
           f"{selector}:hover {{ background: {emboss_gradient(hover)}; }}"
           f"{selector}:pressed {{ background: {emboss_gradient(down, pressed=True)}; }}")
    if checked_color is not None:
        lit = checked_color
        text = f" color: {checked_text};" if checked_text else ""
        qss += (f"{selector}:checked {{ background: {emboss_gradient(lit, pressed=True)};"
                f" {emboss_edges(lit)}{text} }}"
                f"{selector}:checked:hover {{ background:"
                f" {emboss_gradient(lit.darker(HOVER_DARKER), pressed=True)}; }}")
    return qss


def button_emboss_qss(button: QColor) -> str:
    """Global rule for every non-flat QPushButton. Flat buttons (the version
    button, the cancel-transfer ✕) opt out by being flat; the transport's bpm
    button is flat inside a box that carries the look instead."""
    return button_face_qss(
        "QPushButton:!flat", button,
        extra="padding: 3px 12px; min-height: 1.3em;",
        checked_color=button.darker(PRESSED_DARKER)) + \
        "QPushButton:!flat:default { border-color: palette(highlight); }" \
        "QPushButton:!flat:disabled { color: palette(mid); }"


def installed_families() -> set[str]:
    """Families Qt can actually resolve on this machine."""
    return set(QFontDatabase.families())


def auto_now_playing_family() -> str | None:
    """Best available face from NOW_PLAYING_FALLBACKS, or None for the app font.

    Deliberately uncached: a cache would go stale for tests that stub
    QFontDatabase, and for a font installed while the app is running.
    """
    families = installed_families()
    return next((f for f in NOW_PLAYING_FALLBACKS if f in families), None)


def now_playing_font_family(prefs) -> str | None:
    """Family the now-playing panel should use, or None for the app default.

    prefs["now_playing_font"] semantics:
      - missing/None : automatic → best available face from the fallback chain
      - ""           : user chose "same as the app" → always the app default
      - "Family"     : user picked a family → use it, or fall back to automatic
                       if it has since been uninstalled

    Never prompts and never blocks; an unavailable wish quietly becomes the
    nearest thing installed.
    """
    saved = prefs.get("now_playing_font")
    if saved == "":
        return None
    if saved:  # a previously chosen family
        return saved if saved in installed_families() else auto_now_playing_family()
    return auto_now_playing_family()