v0.46.0: scrollbars lose their arrows; the thumb is embossed like a button

The app style now paints the scrollbars itself: the trough runs the full length with no arrow buttons, and the thumb gets the buttons' 4 px corners and emboss, with rims as tall in pixels as a button's however long the thumb. Bar thickness moved from QSS to the style's pixel metric, since any QSS rule on a scrollbar part makes Qt draw the whole bar, arrows included.
2026-10-10 10:44:05 -07:00
parent c312751c86
commit 617402657f
4 changed files with 223 additions and 13 deletions
@@ -0,0 +1,100 @@
+"""Round 80: scrollbars lose their arrow buttons, and the thumb is a button.
+
+- No arrows: the trough runs the bar's full length and the arrow rects are
+  empty, so nothing paints or hit-tests there.
+- The thumb gets the buttons' corner radius and emboss, with rims as tall in
+  pixels as a button's, however long the thumb.
+- The bar's thickness comes from the UI scale through the style, not QSS
+  (any QSS rule on a scrollbar part makes Qt draw the arrows itself).
+"""
+from PyQt6.QtCore import Qt
+from PyQt6.QtGui import QColor
+from PyQt6.QtWidgets import QPushButton, QScrollBar, QStyle, QStyleOptionSlider
+
+from lintunes import theme
+from lintunes.gui.track_table import ClickToJumpScrollStyle
+
+SC = QStyle.SubControl
+
+
+def _option(bar):
+    opt = QStyleOptionSlider()
+    bar.initStyleOption(opt)
+    return opt
+
+
+def _bar(qapp, orientation=Qt.Orientation.Vertical):
+    bar = QScrollBar(orientation)
+    bar.setStyle(ClickToJumpScrollStyle())
+    bar.setRange(0, 900)
+    bar.setPageStep(100)
+    bar.resize(14, 400) if orientation == Qt.Orientation.Vertical \
+        else bar.resize(400, 14)
+    return bar
+
+
+def test_no_arrow_buttons(qapp):
+    bar = _bar(qapp)
+    style, opt = bar.style(), _option(bar)
+    cc = QStyle.ComplexControl.CC_ScrollBar
+    assert style.subControlRect(cc, opt, SC.SC_ScrollBarAddLine, bar).isEmpty()
+    assert style.subControlRect(cc, opt, SC.SC_ScrollBarSubLine, bar).isEmpty()
+    assert style.subControlRect(cc, opt, SC.SC_ScrollBarGroove, bar) == opt.rect
+
+
+def test_thumb_spans_the_full_trough(qapp):
+    for orientation in (Qt.Orientation.Vertical, Qt.Orientation.Horizontal):
+        bar = _bar(qapp, orientation)
+        style, cc = bar.style(), QStyle.ComplexControl.CC_ScrollBar
+        bar.setValue(0)
+        top = style.subControlRect(cc, _option(bar), SC.SC_ScrollBarSlider, bar)
+        bar.setValue(900)
+        end = style.subControlRect(cc, _option(bar), SC.SC_ScrollBarSlider, bar)
+        if orientation == Qt.Orientation.Vertical:
+            assert top.top() == 0 and end.bottom() == 399
+            assert top.height() == 40           # 100 / (900 + 100) of 400
+        else:
+            assert top.left() == 0 and end.right() == 399
+
+
+def test_tiny_page_keeps_a_grabbable_thumb(qapp):
+    bar = _bar(qapp)
+    bar.setRange(0, 100000)
+    rect = bar.style().subControlRect(QStyle.ComplexControl.CC_ScrollBar,
+                                      _option(bar), SC.SC_ScrollBarSlider, bar)
+    assert rect.height() == ClickToJumpScrollStyle.extent * 2
+
+
+def test_thickness_follows_ui_scale(qapp):
+    class Prefs(dict):
+        def get(self, key, default=None):
+            return "large" if key == "ui_scale" else default
+    before = ClickToJumpScrollStyle.extent
+    try:
+        theme.apply_theme(qapp, Prefs())
+        assert ClickToJumpScrollStyle.extent == theme.UI_SCALES["large"]["scrollbar"]
+        assert "QScrollBar" not in qapp.styleSheet()
+    finally:
+        ClickToJumpScrollStyle.extent = before
+
+
+def test_thumb_rims_match_a_real_button(qapp):
+    qapp.setStyleSheet(theme.button_emboss_qss(QColor("#d0d0d0")))
+    try:
+        button = QPushButton("OK")
+        height = button.sizeHint().height()
+        assert abs(theme.button_rim_px(button.fontMetrics())
+                   - theme.EMBOSS_RIM_WIDTH * height) < 1
+    finally:
+        qapp.setStyleSheet("")
+
+
+def test_thumb_paints(qapp):
+    bar = _bar(qapp)
+    bar.setValue(450)
+    image = bar.grab().toImage()
+    thumb = bar.style().subControlRect(QStyle.ComplexControl.CC_ScrollBar,
+                                       _option(bar), SC.SC_ScrollBarSlider, bar)
+    trough = image.pixelColor(7, 5)
+    middle = image.pixelColor(7, thumb.center().y())
+    assert middle != trough