Refactor InitProgressbarAnimation & avoid style cast issue

[DavidGBrett]

Should close #4348

Bug Fix

Avoids the creation of a new style based on PendingLineStyle as there seems to be a WPF bug in handling cloning of styles containing SystemAccentColors - seemingly the trigger for #4348 and other related issues.
That new style was created to add a trigger to play an animation if the progress bar is visible, so instead I moved that to an event handler.

Refactor

• Generally improved the maintainability and readability of the method by being more explicit and using named variables where possible.
• The length of the progress bar is now calculated based on the existing rect values in the xaml instead of a hardcoded value matching them.
• While effectively the same right now, used the progress bar's actual width instead of the windows for the distance it needs to travel, more explicit and will work better if we want to change that.
• Only start the animation if the progress bar is actually visible on the screen, instead of just when its visibility is set

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Summary by cubic

Refactors the progress bar animation to start/stop based on true visibility and moves style usage to XAML to avoid the style/brush cloning cast issue. Fixes the progress bar styling problem (see #4348) and simplifies the animation logic.

Summary of changes

• Changed: Build a single _progressBarStoryboard with explicit targets; use ProgressBar.ActualWidth and dynamic length; keep animations Freeze()d; set PendingLineStyle in XAML via DynamicResource; use ProgressBar.IsVisible instead of Visibility.
• Added: IsVisibleChanged handler to begin/stop the storyboard only when the bar is truly visible.
• Removed: On-the-fly Style creation with visibility Trigger, BeginStoryboard/StopStoryboard, and storyboard name registration.
• Memory impact: Lower allocations by avoiding per-instance style cloning; one storyboard field retained; frozen animations.
• Security risks: None.
• Unit tests: No new tests (UI animation change).

Release Note
The progress bar animates more reliably and displays correctly, fixing a visual glitch.

^{Written for commit 238162a. Summary will update on new commits.}

[coderabbitai]

📝 Walkthrough

Walkthrough

Refactors progress-bar animation in MainWindow to use a stored Storyboard started/stopped on visibility changes and adds a dynamic PendingLineStyle binding to the ProgressBar Line.

Changes

Progress Bar Animation Control

Layer / File(s)	Summary
Animation initialization and visibility wiring Flow.Launcher/MainWindow.xaml.cs	Adds a private _progressBarStoryboard field; InitProgressbarAnimation now constructs and freezes two DoubleAnimations targeting Line.X1/Line.X2, stores the Storyboard, re-subscribes ProgressBar.IsVisibleChanged, and sets the VM ProgressBarVisibility to Hidden. ProgressBar_IsVisibleChanged begins or stops the stored Storyboard.
ProgressBar style binding Flow.Launcher/MainWindow.xaml	Sets the ProgressBar Line element Style to {DynamicResource PendingLineStyle}.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related issues

• BUG: Intermittent System.InvalidCastException in InitProgressbarAnimation when system colors change #4401: Modifies MainWindow progress-bar storyboard creation/management; likely related to animation lifecycle changes.
• BUG: Unable to cast object of type 'System.Windows.Media.Color' to type 'System.Windows.Expression' #4348: Previously reported casting exception in InitProgressbarAnimation when style/template logic ran; this PR's removal/rework of style/trigger assignment may address that failure.

Possibly related PRs

• Flow-Launcher/Flow.Launcher#4313: Also changes progress-bar initialization/start timing and lifecycle in MainWindow.

Suggested reviewers

• jjw24
• Jack251970

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately summarizes the main changes: refactoring InitProgressbarAnimation and avoiding a style cast issue, which directly matches the PR objectives.
Linked Issues check	✅ Passed	The PR addresses the linked issue #4348 by eliminating runtime style/brush cloning that triggered the InvalidCastException. The changes implement XAML-based style definition and visibility-driven animation control as required.
Out of Scope Changes check	✅ Passed	All changes are focused on refactoring the progress bar animation in MainWindow.xaml and MainWindow.xaml.cs to address the specific casting issue, with no unrelated modifications detected.
Description check	✅ Passed	The PR description clearly describes the bug fix addressing issue #4348 (WPF style cloning issue with SystemAccentColors) and the refactoring changes to the progress bar animation logic, directly relating to the changeset.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix-InitProgressbarAnimation-avoid-style-creation

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[cubic-dev-ai]

1 issue found across 2 files

<sub>Reply with feedback, questions, or to request a fix.

Re-trigger cubic</sub>