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WIP: Display download progress for file downloads
Display a vanilla progress bar for file downloads that simply shows how much of the file has been downloaded so far. A new FileDownloadProgressBar widget replaces the existing animated spinner, and we inject a signal through to the SDK to pass the current progress back to the widget. The widget both displays the overall total progress as a percentage and also calculates the download speed by using an exponential moving average to smooth it out. A timer runs every 100ms to recalculate the speed. A new utils.humanize_speed() is used to translate the raw bytes/second into a human-readable version with a focus on keeping the length of the string roughly consistent so there's less visual shifting. TODO: * Visual alignment issue; need padding on the right side * tests? Fixes #1104.
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,82 @@ | ||
| import math | ||
| import time | ||
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| from PyQt5.QtCore import QTimer, pyqtSignal | ||
| from PyQt5.QtWidgets import QProgressBar | ||
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| from securedrop_client.sdk import ProgressProxy | ||
| from securedrop_client.utils import humanize_speed | ||
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| SMOOTHING_FACTOR = 0.3 | ||
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| class FileDownloadProgressBar(QProgressBar): | ||
| """ | ||
| A progress bar for file downloads. | ||
| It receives progress updates from the SDK and updates the total % downloaded, | ||
| as well as calculating the current speed. | ||
| We use an exponential moving average to smooth out the speed as suggested by | ||
| https://stackoverflow.com/a/3841706; the reported speed is 30% of the current | ||
| speed and 70% of the previous speed. It is updated every 100ms. | ||
| """ | ||
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| signal = pyqtSignal(int) | ||
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| def __init__(self, file_size: int) -> None: | ||
| super().__init__() | ||
| self.setObjectName("FileDownloadProgressBar") | ||
| self.setMaximum(file_size) | ||
| # n.b. we only update the bar's value and let the text get updated by | ||
| # the timer in update_speed | ||
| self.signal.connect(self.setValue) | ||
| self.timer = QTimer(self) | ||
| self.timer.setInterval(100) | ||
| self.timer.timeout.connect(self.update_speed) | ||
| self.timer.start() | ||
| # The most recently calculated speed | ||
| self.speed = 0.0 | ||
| # The last time we updated the speed | ||
| self.last_total_time = 0.0 | ||
| # The number of bytes downloaded the last time we updated the speed | ||
| self.last_total_bytes = 0 | ||
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| def update_display(self) -> None: | ||
| """Update the text displayed in the progress bar.""" | ||
| # Use math.floor so we don't show 100% until we're actually done | ||
| percentage = math.floor((self.value() / self.maximum()) * 100) | ||
| formatted_speed = humanize_speed(self.speed) | ||
| # TODO: localize this? | ||
| if percentage in (0, 100): | ||
| # If haven't started or have finished, don't display a 0B/s speed | ||
| self.setFormat(f"{percentage}%") | ||
| else: | ||
| self.setFormat(f"{percentage}% | {formatted_speed}") | ||
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| def update_speed(self) -> None: | ||
| """Calculate the new speed and trigger updating the display.""" | ||
| now = time.monotonic() | ||
| value = self.value() | ||
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| # If this is the first update we report the speed as 0 | ||
| if self.last_total_time == 0: | ||
| self.last_total_time = now | ||
| self.last_total_bytes = value | ||
| self.speed = 0 | ||
| return | ||
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| time_diff = now - self.last_total_time | ||
| bytes_diff = value - self.last_total_bytes | ||
| if time_diff > 0: | ||
| self.speed = ( | ||
| 1 - SMOOTHING_FACTOR | ||
| ) * self.speed + SMOOTHING_FACTOR * bytes_diff / time_diff | ||
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| self.last_total_time = now | ||
| self.last_total_bytes = value | ||
| self.update_display() | ||
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| def proxy(self) -> ProgressProxy: | ||
| """Get a proxy that updates this widget.""" | ||
| return ProgressProxy(self.signal) |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,15 @@ | ||
| from PyQt5.QtCore import pyqtBoundSignal | ||
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| class ProgressProxy: | ||
| """ | ||
| Relay the current download progress over to the UI; see | ||
| the FileDownloadProgressBar widget. | ||
| """ | ||
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| def __init__(self, inner: pyqtBoundSignal | None) -> None: | ||
| self.inner = inner | ||
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| def set_value(self, value: int) -> None: | ||
| if self.inner: | ||
| self.inner.emit(value) |
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