qtflex - responsive width adaptation for Qt

Qt widgets don't adapt their labels to available width. qtflex adds a small, cooperating set: a container that measures and broadcasts a width CLASS, and consumers (action bars, tree headers) that adapt to it - CSS-media-query thinking, but content-driven instead of pixel breakpoints. Plus FloorCap: a one-line fix for child widgets that hard-floor your window's minimum size.

Bindings: PySide6 (tested live), PyQt6 (import-smoked), PySide2/PyQt5 (supported by the shim, untested). Zero dependencies beyond your Qt binding.

ResponsiveContainer

A width-broadcasting parent. Emits width_class_changed(str) with 'full' | 'compact' | 'min', classified against the CONTENT (member children's natural width vs available), not magic px:

• full: everything fits at natural width
• compact: fits only when children shrink (>= 60% of natural)
• min: the floor

API: add(w, member=True) (member widths define the breakpoints), add_layout(l), add_stretch(), layout_box(), width_class property.

Implementation note: a Qt container cannot shrink below its children's minimumSizeHint, so the container uses Ignored horizontal size policy and classifies against the resize EVENT width, never self.width().

ResponsiveBar

An action bar that degrades gracefully as width shrinks, in order:

1. PROMOTE: restore wider label tiers while they fit
2. compress spacing (max_spacing -> min_spacing)
3. DEMOTE: the widest button with a shorter tier drops one tier (repeat)
4. SPILL: at the tier floor, lowest-priority buttons hide into a » overflow menu (menu label = shortest tier, click = original handler). The bar is never fully empty - the highest-priority button always stays visible.

API:

• add_button(tiers, tooltip=None, on_click=None, style=None, cursor=True, priority=100) - tiers is a list widest->shortest, e.g. ["Re-read all ({n})", "Re-read {n}", "RR"]; {n} templates update via set_count(btn, n). Lower priority spills first. Returns the QPushButton.
• add_widget(w) - fixed pass-through widget (dropdown, LED), never demoted.
• add_stretch()
• subscribe_to(container) - drive layout from a ResponsiveContainer; bars sharing one container demote in concert. Without it the bar self-measures via its own resizeEvent.

Constructor: min_spacing=1, max_spacing=6, margins=(5, 0, 5, 5), spill=True, demote="staged", compact_counts=False.

• spill=False: buttons stop at their shortest tier, no overflow menu; below the floor they shrink proportionally (elide) rather than paint past the bar's edges.
• demote="staged" (default): buttons demote one step at a time, ordered by the tier FRACTION the step would reach - unequal tier-list lengths degrade proportionally, no button hits its floor while others sit untouched. Promotion mirrors this: the deepest-demoted (by fraction) recovers first, with a hysteresis band so boundary widths never flap. ("uniform" reserved, not yet implemented.)
• compact_counts=True: {n} counts render as 1.1k / 2.3M above 999, keeping label width bounded as counts grow. set_count re-runs the layout, so a growing number can trigger demotion without a resize.

Tier state is tracked internally (never re-derived from button text) - count changes cannot desync the tier machine.

Driving the bar from a parent widget instead of a ResponsiveContainer: set bar._driven = True and call bar._apply_layout(bar.width()) from the parent's resizeEvent. Exactly ONE width source per bar - a bar fed by two sources (own resizeEvent + a parent driver) will oscillate.

ResponsiveHeader

Column collapse for QTreeView/QTreeWidget, same priority vocabulary. ResponsiveHeader(tree, {2: 10, 3: 20}) - lower priority hides first; column 0 is never hidden; unlisted columns default to priority 100. apply(width_class): full = all shown; compact = hide 1; min = hide half. subscribe_to(container) joins the same broadcast.

Wiring

from qtflex import ResponsiveBar, ResponsiveContainer, ResponsiveHeader

cont = ResponsiveContainer()
bar = ResponsiveBar()
cont.add(bar)
bar.subscribe_to(cont)
hdr = ResponsiveHeader(tree, {2: 10, 3: 20})
hdr.subscribe_to(cont)

qtcompat

Internal binding shim (PySide6 > PySide2 > PyQt6 > PyQt5, first importable wins); Signal normalized across PySide/PyQt. qtflex.QT_BINDING names the active binding.

FloorCap - stop child widgets from hard-flooring your window

Qt sums every child's minimumSizeHint into the window's hard minimum; a multi-pane panel can silently block window-edge resize at ~window width. setSizePolicy(Ignored) does NOT shrink the hint - only an override does.

from qtflex import FloorCap, floor_cap

class MyPanel(FloorCap, QWidget):   # mixin form
    FLOOR_W = 200

Capped = floor_cap(SomePanel, w=200)  # wrapper form

License

MIT