OS animations and smooth scrolling for nextOS 2.5.0 by Copilot · Pull Request #8 · dynodevv/nextOS

Copilot · 2026-02-18T16:47:39Z

Implements a comprehensive animation system and pixel-level smooth scrolling for nextOS, providing a modern, fluid experience that matches the skeuomorphic design aesthetic.

Animation System

Window open: Slide-up + fade-in (200ms) with ease-out cubic easing
Window close: Fade-out + slide-down with deferred destruction (150ms)
Window minimize/unminimize: GNOME-like stretch animation — animates position AND size from window to taskbar button and back (250ms), with fade
Window maximize/restore: Stretch animation from old geometry to new geometry (200ms) with canvas scaling via nearest-neighbor sampling
Start menu: Slide-up/down + fade (150ms)

Animation state is tracked per-window with anim_from_x/y/w/h and anim_to_x/y/w/h fields. The minimize/unminimize lifecycle is symmetric — both update the minimized flag only at animation completion.

Z-order Animation Bug Fix

Window and start menu animations previously blended toward the wallpaper cache during fading, causing windows behind the animated window to briefly disappear. Fixed by saving background pixels before drawing the animated element, then blending against the saved snapshot instead of the wallpaper. Applied to both window and start menu animations.

Smooth Scrolling

The initial fixed-point ×256 accumulator approach never worked — integer division always rounded fractional values to 0. Redesigned with a pixel-level accumulator:

Each raw scroll notch adds 120px to smooth_scroll_accum
Each frame releases 30% of remaining pixels (min 2px), producing ease-out deceleration over ~12 frames (~96ms)
Pixel-based apps (notepad, browser): use compositor_get_smooth_scroll() directly as pixel delta
Row-based apps (explorer, settings): use raw compositor_get_scroll() since discrete row indexing can't benefit from sub-row interpolation

Files Changed

File	Description
`kernel/ui/compositor.h`	Animation type defines, window animation state fields, `compositor_get_smooth_scroll()` declaration
`kernel/ui/compositor.c`	Smooth scroll accumulator, animation system with ease-out cubic easing, deferred destruction, canvas scaling, alpha blending with background saving, start menu animations
`apps/notepad/notepad.c`	Switched to `compositor_get_smooth_scroll()`, removed per-notch multiplier
`apps/browser/browser.c`	Switched to `compositor_get_smooth_scroll()`, removed per-notch multiplier
`apps/explorer/explorer.c`	Uses raw `compositor_get_scroll()` for row-based scrolling
`apps/settings/settings.c`	Uses raw `compositor_get_scroll()` for row-based scrolling

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Add animation engine to compositor with ease-out cubic easing: - Window open: slide-up + fade-in (200ms) - Window close: fade-out + slide-down with deferred destruction (150ms) - Window minimize: slide to taskbar + fade-out (250ms) - Window unminimize: slide from taskbar + fade-in (250ms) - Window maximize/restore: fade transition (200ms) - Start menu: slide-up/down + fade (150ms) Animation state tracked per-window with timer-based progress. Hit-testing skips windows in close/minimize animations. Fade overlay blends window pixels towards wallpaper cache. Co-authored-by: dynodevv <85120286+dynodevv@users.noreply.github.com>

Co-authored-by: dynodevv <85120286+dynodevv@users.noreply.github.com>

…nt smooth scrolling 1. Z-order bug fix: Save background pixels before drawing animated window, then blend between saved background and drawn window. This correctly shows windows behind during close/minimize animations instead of the wallpaper bleeding through. 2. GNOME-like stretch animations: Maximize/restore/minimize/unminimize now animate position AND size (stretch effect). Canvas is scaled during animation using nearest-neighbor sampling. Added anim_from_w/h and anim_to_w/h fields to window_t struct. 3. Smooth scrolling: Added compositor_get_smooth_scroll() API that provides interpolated scroll values. Scroll input accumulates into a target, which is smoothly interpolated at ~30% per frame. All 4 apps (notepad, browser, explorer, settings) updated to use it. Co-authored-by: dynodevv <85120286+dynodevv@users.noreply.github.com>

Apply the same bg_save technique to the start menu animation that was applied to window animations. Previously the start menu fade blended toward wallpaper, but it sits above the taskbar, so fading should show the taskbar behind it. Co-authored-by: dynodevv <85120286+dynodevv@users.noreply.github.com>

- Add cw > 0 && ch > 0 check to canvas blit to prevent out-of-bounds access when source canvas dimensions are very small - Fix smooth scroll: snap small remainders (< 256 fixed-point) to prevent scroll values from getting stuck and never draining Co-authored-by: dynodevv <85120286+dynodevv@users.noreply.github.com>

The previous smooth scroll implementation used a fixed-point x256 accumulator that delivered fractional scroll notches. This never worked because integer division always rounded fractional values to 0, causing the snap-to-±1 fallback to make scrolling identical to raw/choppy. New approach: - Raw scroll notches converted to pixel targets (120px per notch) - Each frame releases 30% of remaining pixels (min 2px), creating natural ease-out deceleration over ~12 frames (~96ms) - Pixel-based apps (notepad, browser) receive smooth pixel deltas directly, removing their per-notch multipliers - Row-based apps (explorer, settings) use raw compositor_get_scroll() since they can't do sub-row scrolling Co-authored-by: dynodevv <85120286+dynodevv@users.noreply.github.com>

Copilot

Pull request overview

This PR claims to fix smooth scrolling but actually includes two major feature additions: (1) a pixel-level smooth scrolling system and (2) a comprehensive window/menu animation system with ease-out cubic easing. The PR description only mentions the smooth scrolling changes.

Changes:

Pixel-level smooth scrolling with 30% per-frame ease-out interpolation (accumulator + gradual release)
Complete animation system: window open/close/minimize/unminimize/maximize/restore animations with canvas scaling, alpha blending, and background saving
Start menu slide+fade animations
Updated notepad and browser to use pixel-based smooth scrolling API

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
kernel/ui/compositor.h	Added animation type defines, window animation state fields, and compositor_get_smooth_scroll() declaration
kernel/ui/compositor.c	Implemented smooth scroll accumulator/interpolation, complete animation system with ease-out cubic easing, deferred window destruction, canvas scaling during animations, alpha blending with background saving, start menu animations
apps/notepad/notepad.c	Switched to compositor_get_smooth_scroll() and removed LINE_HEIGHT multiplier
apps/browser/browser.c	Switched to compositor_get_smooth_scroll() and removed pixel multiplier

Copilot · 2026-02-18T18:34:00Z

@@ -959,6 +1264,16 @@ void compositor_handle_mouse(int mx, int my, int buttons, int scroll)
                if (mx >= bx && mx < bx + 120) {
                    if (windows[i].minimized) {
                        windows[i].minimized = 0;


Inconsistency in animation lifecycle: unminimize sets minimized = 0 immediately (line 1266), but minimize waits until animation completion to set minimized = 1 (line 1121). While the current code works due to the draw_window conditional checking both minimized and anim_type, this asymmetry is confusing and could lead to bugs. Consider moving this line to the ANIM_UNMINIMIZE finalization case (after line 1124) to match the minimize pattern and make the code more maintainable.

Fixed in 455d40a. Moved minimized = 0 from the click handler to the ANIM_UNMINIMIZE finalization case, matching the minimize pattern. Both now update minimized at animation completion.

Copilot · 2026-02-18T18:34:00Z

+/* ── Animation types ──────────────────────────────────────────────────── */
+#define ANIM_NONE        0
+#define ANIM_OPEN        1
+#define ANIM_CLOSE       2
+#define ANIM_MINIMIZE    3
+#define ANIM_UNMINIMIZE  4
+#define ANIM_MAXIMIZE    5
+#define ANIM_RESTORE     6
+


The PR title and description focus solely on fixing smooth scrolling, but the changes include a complete window animation system (open, close, minimize, unminimize, maximize, restore animations with ease-out cubic easing, canvas scaling during animations, alpha blending with background saving, start menu animations, etc.). This extensive animation system is not mentioned in the PR description. While these features may be valuable, bundling them with the smooth scrolling fix makes the PR harder to review and increases risk. Consider splitting these into separate PRs: one for smooth scrolling fixes and another for the animation system.

dynodevv · 2026-02-18T18:34:39Z

@copilot apply changes based on the comments in this thread

Move minimized=0 from the click handler to the ANIM_UNMINIMIZE finalization case, matching the minimize pattern which sets minimized=1 at animation completion. This makes the minimize/ unminimize lifecycle symmetric and less error-prone. Co-authored-by: dynodevv <85120286+dynodevv@users.noreply.github.com>

Copilot · 2026-02-18T18:36:31Z

@copilot apply changes based on the comments in this thread

Applied the lifecycle fix from the review in 455d40a — unminimize now defers minimized = 0 to animation completion, matching the minimize pattern. The PR scope comment is noted but these features were developed together across the prior issue threads.

Initial plan

6fdb31d

Copilot AI assigned Copilot and dynodevv Feb 18, 2026

Copilot started work on behalf of dynodevv February 18, 2026 16:48 View session

Copilot AI and others added 2 commits February 18, 2026 17:02

Fix ease_out_cubic guard to use uint64_t comparison for safety

10e6648

Co-authored-by: dynodevv <85120286+dynodevv@users.noreply.github.com>

Copilot AI changed the title ~~[WIP] Add OS animations for nextOS 2.5.0~~ Add compositor animation system for nextOS 2.5.0 Feb 18, 2026

Copilot AI requested a review from dynodevv February 18, 2026 17:08

Copilot finished work on behalf of dynodevv February 18, 2026 17:09

Copilot started work on behalf of dynodevv February 18, 2026 17:41 View session

Copilot AI and others added 3 commits February 18, 2026 17:46

Copilot AI changed the title ~~Add compositor animation system for nextOS 2.5.0~~ Fix animation z-order bug, add GNOME-like stretch animations, implement smooth scrolling Feb 18, 2026

Copilot finished work on behalf of dynodevv February 18, 2026 17:54

Copilot started work on behalf of dynodevv February 18, 2026 18:01 View session

Copilot AI changed the title ~~Fix animation z-order bug, add GNOME-like stretch animations, implement smooth scrolling~~ Fix smooth scrolling: redesign from broken fixed-point accumulator to pixel-level ease-out Feb 18, 2026

Copilot finished work on behalf of dynodevv February 18, 2026 18:07

dynodevv marked this pull request as ready for review February 18, 2026 18:28

Copilot AI review requested due to automatic review settings February 18, 2026 18:28

Copilot started reviewing on behalf of dynodevv February 18, 2026 18:29 View session

Copilot AI reviewed Feb 18, 2026

View reviewed changes

Copilot started work on behalf of dynodevv February 18, 2026 18:35 View session

Copilot AI changed the title ~~Fix smooth scrolling: redesign from broken fixed-point accumulator to pixel-level ease-out~~ OS animations and smooth scrolling for nextOS 2.5.0 Feb 18, 2026

Copilot finished work on behalf of dynodevv February 18, 2026 18:37

dynodevv merged commit 3d3d6dd into main Feb 18, 2026
1 check passed

dynodevv deleted the copilot/implement-os-animations branch February 18, 2026 18:41

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OS animations and smooth scrolling for nextOS 2.5.0#8

OS animations and smooth scrolling for nextOS 2.5.0#8
dynodevv merged 8 commits intomainfrom
copilot/implement-os-animations

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Animation System

Z-order Animation Bug Fix

Smooth Scrolling

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Copilot AI commented Feb 18, 2026 •

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