Start work on central widget for main window

src/calibre/gui2/central.py

@@ -0,0 +1,268 @@
+#!/usr/bin/env python
+# License: GPLv3 Copyright: 2023, Kovid Goyal <kovid at kovidgoyal.net>
+
+from enum import Enum, auto
+from qt.core import (
+    QDialog, QLabel, QPalette, QPointF, QSize, QSizePolicy, QStyle, QStyleOption,
+    QStylePainter, Qt, QVBoxLayout, QWidget, pyqtSignal
+)
+
+from calibre.gui2 import Application, config
+
+
+class Placeholder(QLabel):
+    backgrounds = 'yellow', 'lightgreen', 'grey', 'cyan', 'magenta'
+    bgcount = 0
+
+    def __init__(self, text, parent=None):
+        super().__init__(text, parent)
+        bg = self.backgrounds[Placeholder.bgcount]
+        Placeholder.bgcount = (Placeholder.bgcount + 1) % len(self.backgrounds)
+        self.setStyleSheet(f'QLabel {{ background: {bg} }}')
+
+
+class HandleState(Enum):
+    both_visible = auto()
+    only_main_visible = auto()
+    only_side_visible = auto()
+
+
+class SplitterHandle(QWidget):
+
+    drag_started = pyqtSignal()
+    drag_ended = pyqtSignal()
+    dragged_to = pyqtSignal(QPointF)
+    drag_start = None
+
+    def __init__(self, parent: QWidget=None, orientation: Qt.Orientation = Qt.Orientation.Vertical):
+        super().__init__(parent)
+        self.orientation = orientation
+        if orientation is Qt.Orientation.Vertical:
+            self.setCursor(Qt.CursorShape.SplitHCursor)
+        else:
+            self.setCursor(Qt.CursorShape.SplitVCursor)
+
+    @property
+    def state(self) -> HandleState:
+        p = self.parent()
+        if p is not None:
+            try:
+                return p.handle_state(self)
+            except AttributeError as err:
+                raise Exception(str(err)) from err
+        return HandleState.both_visible
+
+    def mousePressEvent(self, ev):
+        super().mousePressEvent(ev)
+        if ev.button() is Qt.MouseButton.LeftButton:
+            self.drag_start = ev.position()
+            self.drag_started.emit()
+
+    def mouseReleaseEvent(self, ev):
+        super().mouseReleaseEvent(ev)
+        if ev.button() is Qt.MouseButton.LeftButton:
+            self.drag_start = None
+            self.drag_started.emit()
+
+    def mouseMoveEvent(self, ev):
+        super().mouseMoveEvent(ev)
+        if self.drag_start is not None:
+            pos = ev.position() - self.drag_start
+            self.dragged_to.emit(self.mapToParent(pos))
+
+    def paintEvent(self, ev):
+        p = QStylePainter(self)
+        opt = QStyleOption()
+        opt.initFrom(self)
+        if self.orientation is Qt.Orientation.Vertical:
+            opt.state |= QStyle.StateFlag.State_Horizontal
+        if self.state is HandleState.only_side_visible:
+            p.fillRect(opt.rect, opt.palette.color(QPalette.ColorRole.Window))
+        else:
+            p.drawControl(QStyle.ControlElement.CE_Splitter, opt)
+        p.end()
+
+
+class Layout(Enum):
+
+    wide = auto()
+    narrow = auto()
+
+
+class WideDesires:
+    tag_browser_width = book_details_width = None
+    cover_browser_height = quickview_height = None
+
+
+class Visibility:
+    tag_browser = book_details = book_list = True
+    cover_browser = quick_view = False
+
+
+class Central(QWidget):
+
+    def __init__(self, parent=None, initial_layout=''):
+        super().__init__(parent)
+        self.setSizePolicy(QSizePolicy.Policy.Expanding, QSizePolicy.Policy.Expanding)
+        self.wide_desires = WideDesires()
+        self.is_visible = Visibility()
+        self.layout = Layout.narrow if (initial_layout or config.get('gui_layout')) == 'narrow' else Layout.wide
+        self.tag_browser = Placeholder('tag browser', self)
+        self.book_list = Placeholder('book list', self)
+        self.cover_browser = Placeholder('cover browser', self)
+        self.book_details = Placeholder('book details', self)
+        self.quick_view = Placeholder('quick view', self)
+
+        def h(orientation: Qt.Orientation = Qt.Orientation.Vertical):
+            ans = SplitterHandle(self, orientation)
+            ans.dragged_to.connect(self.splitter_handle_dragged)
+            return ans
+
+        self.left_handle = h()
+        self.right_handle = h()
+        self.top_handle = h(Qt.Orientation.Horizontal)
+        self.bottom_handle = h(Qt.Orientation.Horizontal)
+
+    def handle_state(self, handle):
+        if self.layout is Layout.wide:
+            return self.wide_handle_state(handle)
+        return self.narrow_handle_state(handle)
+
+    def splitter_handle_dragged(self, pos):
+        handle = self.sender()
+        if self.layout is Layout.wide:
+            self.wide_move_splitter_handle_to(handle, pos)
+        else:
+            self.narrow_move_splitter_handle_to(handle, pos)
+
+    def refresh_after_config_change(self):
+        self.layout = Layout.narrow if config.get('gui_layout') == 'narrow' else Layout.wide
+        self.relayout()
+
+    def resizeEvent(self, ev):
+        super().resizeEvent(ev)
+        self.relayout()
+
+    def relayout(self):
+        self.tag_browser.setVisible(self.is_visible.tag_browser)
+        self.book_details.setVisible(self.is_visible.book_details)
+        self.cover_browser.setVisible(self.is_visible.cover_browser)
+        self.book_list.setVisible(self.is_visible.book_list)
+        self.quick_view.setVisible(self.is_visible.quick_view)
+        if self.layout is Layout.wide:
+            self.do_wide_layout()
+        else:
+            self.do_narrow_layout()
+        self.update()
+
+    # Wide {{{
+    def wide_handle_state(self, handle):
+        if handle is self.left_handle:
+            return HandleState.both_visible if self.is_visible.tag_browser else HandleState.only_main_visible
+        if handle is self.right_handle:
+            return HandleState.both_visible if self.is_visible.book_details else HandleState.only_main_visible
+        if handle is self.top_handle:
+            if self.is_visible.cover_browser:
+                return HandleState.both_visible if self.is_visible.book_list else HandleState.only_side_visible
+            return HandleState.only_main_visible
+        if handle is self.bottom_handle:
+            return HandleState.both_visible if self.is_visible.quick_view else HandleState.only_main_visible
+
+    def do_wide_layout(self):
+        s = self.style()
+        normal_handle_width = int(s.pixelMetric(QStyle.PixelMetric.PM_SplitterWidth, widget=self))
+        available_width = self.width()
+        for h in (self.left_handle, self.right_handle):
+            width = 1
+            hs = h.state
+            if hs is HandleState.both_visible or hs is HandleState.only_side_visible:
+                width = normal_handle_width
+            h.resize(width, self.height())
+            available_width -= width
+        default_width = min(300, (3 * available_width) // 10)
+        tb = self.wide_desires.tag_browser_width or default_width
+        if not self.is_visible.tag_browser:
+            tb = 0
+        bd = self.wide_desires.book_details_width or default_width
+        if not self.is_visible.book_details:
+            bd = 0
+        min_book_list_width = max(200, self.cover_browser.minimumWidth(), available_width // 10)
+        if tb + bd > available_width - min_book_list_width:
+            width_to_share = max(0, available_width - min_book_list_width)
+            tb = int(tb * width_to_share / (tb + bd))
+            bd = width_to_share - tb
+        central_width = available_width - (tb + bd)
+        self.tag_browser.setGeometry(0, 0, tb, self.height())
+        self.left_handle.move(tb, 0)
+        central_x = self.left_handle.x() + self.left_handle.width()
+        self.right_handle.move(tb + central_width + self.left_handle.width(), 0)
+        self.book_details.setGeometry(self.right_handle.x() + self.right_handle.width(), 0, bd, self.height())
+
+        available_height = self.height()
+        for h in (self.top_handle, self.bottom_handle):
+            height = 1
+            hs = h.state
+            if hs is HandleState.both_visible or hs is HandleState.only_side_visible:
+                height = normal_handle_width
+            if h is self.bottom_handle and hs is HandleState.only_main_visible:
+                height = 0
+            h.resize(self.width(), height)
+            available_height -= height
+
+        cb = max(self.cover_browser.minimumHeight(), self.wide_desires.cover_browser_height or (2 * available_height // 5))
+        if not self.is_visible.cover_browser:
+            cb = 0
+        qv = bl = 0
+        if cb >= available_height:
+            cb = available_height
+        else:
+            available_height -= cb
+            min_bl_height = 50
+            if available_height <= min_bl_height:
+                bl = available_height
+            else:
+                qv = min(available_height - min_bl_height, qv)
+                bl = available_height - qv
+        self.cover_browser.setGeometry(central_x, 0, central_width, cb)
+        self.top_handle.move(central_x, cb)
+        self.book_list.setGeometry(central_x, self.top_handle.y() + self.top_handle.height(), central_width, bl)
+        self.bottom_handle.move(central_x, self.book_list.y() + self.book_list.height())
+        self.quick_view.setGeometry(central_x, self.bottom_handle.y() + self.bottom_handle.height(), central_width, qv)
+
+    def wide_move_splitter_handle_to(self, handle: SplitterHandle, pos: QPointF):
+        raise NotImplementedError('TODO: Implement me')
+    # }}}
+
+    # Narrow {{{
+    def narrow_handle_state(self, handle):
+        raise NotImplementedError('TODO: Implement me')
+
+    def narrow_move_splitter_handle_to(self, handle: SplitterHandle, pos: QPointF):
+        raise NotImplementedError('TODO: Implement me')
+
+    def do_narrow_layout(self):
+        raise NotImplementedError('TODO: Implement me')
+    # }}}
+
+    def sizeHint(self):
+        return QSize(800, 600)
+
+
+def develop():
+    app = Application([])
+    class d(QDialog):
+        def __init__(self):
+            super().__init__()
+            l = QVBoxLayout(self)
+            l.setContentsMargins(0, 0, 0, 0)
+            self.central = Central(self)
+            l.addWidget(self.central)
+            self.resize(self.sizeHint())
+
+    d = d()
+    d.show()
+    app.exec()
+
+
+if __name__ == '__main__':
+    develop()