forked from Mirrors/apostrophe
110 lines
3.6 KiB
Python
110 lines
3.6 KiB
Python
import gi
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gi.require_version('WebKit2', '4.0')
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from gi.repository import WebKit2, GLib, GObject
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class WebView(WebKit2.WebView):
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"""A WebView that provides read/write access to scroll.
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It does so using JavaScript, by continuously monitoring it while loaded.
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The alternative is using a WebExtension and C-bindings (see reference), but that is more
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complicated implementation-wise, as well as build-wise until we start building with Meson.
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Reference: https://github.com/aperezdc/webkit2gtk-python-webextension-example
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"""
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GET_SCROLL_SCALE_JS = """
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e = document.documentElement;
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e.scrollHeight > e.clientHeight ? e.scrollTop / (e.scrollHeight - e.clientHeight) : -1;
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"""
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SET_SCROLL_SCALE_JS = """
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scale = {:.16f};
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e = document.documentElement;
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e.scrollTop = (e.scrollHeight - e.clientHeight) * scale;
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"""
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__gsignals__ = {
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"scroll-scale-changed": (GObject.SIGNAL_RUN_LAST, None, (float,)),
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}
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def __init__(self):
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super().__init__()
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self.connect("load-changed", self.on_load_changed)
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self.connect("load-failed", self.on_load_failed)
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self.connect("size-allocate", self.on_size_allocate)
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self.connect("destroy", self.on_destroy)
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self.scroll_scale = 0.0
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self.pending_scroll_scale = None
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self.state_loaded = False
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self.state_load_failed = False
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self.state_waiting = False
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self.timeout_id = None
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def get_scroll_scale(self):
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return self.scroll_scale
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def set_scroll_scale(self, scale):
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self.pending_scroll_scale = scale
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self.state_loop()
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def on_load_changed(self, _web_view, event):
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self.state_loaded = event >= WebKit2.LoadEvent.COMMITTED and not self.state_load_failed
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self.state_load_failed = False
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self.pending_scroll_scale = self.scroll_scale
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self.state_loop()
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def on_load_failed(self, _web_view, _event):
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self.state_loaded = False
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self.state_load_failed = True
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self.state_loop()
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def on_size_allocate(self, *_):
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self.set_scroll_scale(self.scroll_scale)
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def on_destroy(self, _widget):
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self.state_loaded = False
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self.state_loop()
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def read_scroll_scale(self):
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self.state_waiting = True
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self.run_javascript(
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self.GET_SCROLL_SCALE_JS, None, self.sync_scroll_scale)
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def write_scroll_scale(self, scroll_scale):
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self.run_javascript(
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self.SET_SCROLL_SCALE_JS.format(scroll_scale), None, None)
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def sync_scroll_scale(self, _web_view, result):
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self.state_waiting = False
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result = self.run_javascript_finish(result)
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self.state_loop(result.get_js_value().to_double())
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def state_loop(self, scroll_scale=None, delay=16): # 16ms ~ 60hz
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# Remove any pending callbacks
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if self.timeout_id:
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GLib.source_remove(self.timeout_id)
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self.timeout_id = None
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# Set scroll scale if specified, and the state is not dirty
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if scroll_scale not in (None, -1, self.scroll_scale):
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self.scroll_scale = scroll_scale
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self.emit("scroll-scale-changed", self.scroll_scale)
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# Handle the current state
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if not self.state_loaded or self.state_load_failed or self.state_waiting:
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return
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if self.pending_scroll_scale:
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self.write_scroll_scale(self.pending_scroll_scale)
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self.pending_scroll_scale = None
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self.read_scroll_scale()
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elif delay > 0:
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self.timeout_id = GLib.timeout_add(delay, self.state_loop, None, 0)
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else:
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self.read_scroll_scale()
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