tweak(credits): Decouple credits scroll timing from render update

[bobtista]

Summary

• Credits screen scrolling now uses frame delta time instead of frame counting
• Credits scroll at consistent speed regardless of frame rate
• Credits won't jump ahead when tabbing out and back in

Changes

• Replaced m_framesSinceStarted frame counter with m_scrollAccumulator for fractional pixel tracking
• Uses TheFramePacer->getUpdateTime() for frame-rate independent timing
• Accumulates fractional scroll progress and moves whole pixels when accumulator >= 1

Test plan

• Verify credits scroll at the same speed at 30fps and higher frame rates
• Verify credits still scroll smoothly without stuttering
• Verify credits don't jump ahead after tabbing out and back in

30FPS
https://github.com/user-attachments/assets/0215fd82-49f7-4c7c-9903-c8b0f53eb239

60FPS
https://github.com/user-attachments/assets/a45a847b-1f9d-4642-8ab3-23e30de25c04

[greptile-apps]

Greptile Overview

Greptile Summary

Replaced frame-based credits scrolling with time-based scrolling using TheFramePacer->getUpdateTime() for frame-rate independence. The new implementation accumulates fractional pixels per frame and scrolls only when at least 1 whole pixel has accumulated, preserving smooth scrolling across different frame rates. Changes are mirrored across both Generals and GeneralsMD codebases.

Key changes:

• Replaced Int m_framesSinceStarted with Real m_scrollAccumulator to track fractional pixel accumulation
• Added Common/FramePacer.h include for delta time access
• Converted frame-based scroll rate to pixels-per-second using SECONDS_PER_LOGICFRAME_REAL
• Scroll logic now accumulates time-weighted pixels and moves by integer amounts
• Clear, informative inline comments explain the accumulator approach

Confidence Score: 5/5

• This PR is safe to merge with no issues found
• Clean refactoring that correctly converts frame-based timing to time-based timing. The math is sound, implementation is identical across both codebases, includes appropriate comments, and has been tested at multiple frame rates per the test plan
• No files require special attention

Sequence Diagram

sequenceDiagram
    participant Game as Game Loop
    participant Credits as CreditsManager::update()
    participant FramePacer as TheFramePacer
    participant Display as Credits Display

    Game->>Credits: Call update()
    Credits->>Credits: Check if finished
    alt Not finished
        Credits->>FramePacer: getUpdateTime()
        FramePacer-->>Credits: deltaTime (seconds)
        Credits->>Credits: Calculate scrollSpeedPixelsPerSec<br/>=scrollRate/(scrollRatePerFrames*SECONDS_PER_LOGICFRAME_REAL)
        Credits->>Credits: Accumulate: m_scrollAccumulator += deltaTime * scrollSpeedPixelsPerSec
        Credits->>Credits: Cast to Int: pixelsToMove = (Int)m_scrollAccumulator
        alt pixelsToMove >= 1
            Credits->>Credits: Subtract moved pixels: m_scrollAccumulator -= pixelsToMove
            Credits->>Display: Update all credit line positions by pixelsToMove
            Credits->>Display: Remove lines that scrolled off-screen
            Credits->>Display: Add new lines if needed
        else pixelsToMove < 1
            Credits-->>Game: Return (skip this frame)
        end
    else Finished
        Credits-->>Game: Return immediately
    end

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[xezon]

Is the Pull Description up-to-date?

[xezon]

Code looks good. Did not test.