Mobile & Touch

Paint Forge runs natively in mobile browsers without a dedicated app — the editor adapts its UI to the screen size and input device. Touch gestures replace many keyboard shortcuts; the toolbar collapses into a configurable hotbar; panels become bottom sheets that swipe away. This page is the reference for everything mobile- specific.

Touch Gestures

Multi-touch on the canvas drives camera + history. Single-finger gestures drive the active tool (drawing, selecting, etc.) so they don't conflict.

Gesture	Action
Two-finger pinch	Zoom canvas (centered between fingers)
Two-finger rotate	Rotate canvas view (1° per gesture tick)
Two-finger tap	Undo (faster than tapping the toolbar button)
Three-finger tap	Redo. Also cancels QuickShape during the snap-to-shape moment.
Hold ½s mid-stroke	QuickShape — freehand input snaps to the closest clean shape (line, ellipse, rect, polygon). The recognized shape's outline shows; release to keep, lift to commit.
Hold ~1.2s after snap	QuickShape vector commit — converts the snapped shape into an editable vector object instead of a raster stroke.
Long-press (500ms) on hotbar slot	Open the tool grid to assign a different tool to that slot.
Swipe down on a panel	Dismiss the panel without reaching for an X button. Works on Layers, Colors, Properties, etc.
Two-finger drag on canvas	Pan the viewport (when not actively zooming/rotating).

Gestures only fire on the canvas. UI panels still scroll naturally with one finger; the multi-touch handlers are scoped to the canvas overlay so swiping inside Layers doesn't accidentally rotate the canvas.

Tool Hotbar

On phones the left toolbar is replaced with a horizontal hotbar at the bottom of the screen. The hotbar shows your most-used tools as quick-access slots; the slot count auto-fits the viewport so tools never get cut off.

Behavior	Detail
Slot count	Auto-computed from viewport width (portrait) or height (landscape). Range: 4-9 slots. Re-fits on orientation change and resize.
Reassign a slot	Long-press the slot for 500ms; tool grid opens; tap any tool to bind it.
Persistence	Slot configuration saves to localStorage (HOTBAR_SLOTS_KEY). Carries across sessions on the same device.
Layout modes	Three options in Preferences > Tools > Mobile Toolbar Mode: Hotbar (default; fixed slots), Scroll (horizontally scrollable strip of every tool), Hybrid (slots + a More-tools popup).

Landscape orientation

In landscape, the hotbar moves to the right edge of the screen as a vertical pill — it stays out of the way of two-handed tablet drawing where left-hand finger gestures on the canvas are the primary input.

Pen Pressure & Tilt

Paint Forge picks up pressure from any device that exposes a PointerEvent with pointerType === 'pen' — Apple Pencil on iPad, S-Pen on Android, Wacom tablets via stylus, Microsoft Surface Pen, etc. Pressure is a value between 0 and 1; mouse input always reports 1.0.

Modulator	What it drives
Pressure → Size	Stroke radius scales with pen pressure. Light touch = thin line, hard press = full size.
Pressure → Opacity	Alpha scales with pen pressure. Light touch = faded, hard press = full opacity. Common for inking.
Tilt → Opacity	Alpha scales with pen tilt magnitude. Perpendicular pen = full alpha; flat pen ≈ 40% — natural pencil-shading behavior. Requires Apple Pencil 2 / S-Pen / similar tilt-aware stylus.
Velocity → Size	Stroke radius scales inversely with drag speed. Slow drag = full width, fast = tapered. Works on mouse and pen.

Toggle each modulator independently from the active brush's options panel. Save a brush preset to capture your preferred combination across sessions. Each modulator respects the per-tool pressure curve (Linear / Soft / Firm / S-Curve / Custom).

Responsive Panels

On phones, the right sidebar (Layers, Colors, Objects, Library, Canvas) becomes a bottom sheet. The active panel slides up from the screen bottom; swipe down to dismiss. Tabs at the top of the sheet switch between panels without closing.

On tablets in landscape, the sidebar reverts to its full-width docked form on the right edge. The breakpoint is determined by viewport width — aim for ≥768px to keep the desktop layout.

Floating Canvas Controls

The mobile canvas surface ships a small floating-pill bar with the most-used controls: Undo, Redo, current Tool indicator (tap to open the tool grid), Color Picker (with active brush color preview), Layer Cycle (tap forward, long-press backward), Fit to Screen, Fullscreen toggle, Delete Selected (when active), Zoom + and − with current zoom %, plus a rotation badge that shows the canvas angle and resets on tap when rotated.

The pill respects the safe-area inset (notch / Dynamic Island on iOS) and the software keyboard height — it stays usable when the on-screen keyboard pushes other content up.

Performance on Mobile

Mobile GPUs and CPUs vary 10× across consumer devices. Paint Forge ships several knobs to tune for slower hardware:

Knob	When to lower
Painting Frame Rate (Preferences > Tools)	Drop from 60fps to 30fps if brush strokes feel laggy on 2-3 year old budget phones. Saves ~50% paint-time CPU.
Canvas dimensions (File > Canvas Resize)	Anything over 4000×4000px starts to chug on midrange Android. 2048×2048 is the comfort floor for most filter operations.
Max Undo Steps (Preferences > General)	Default 50 steps. Dropping to 25 halves the per-frame undo bookkeeping.
Adjustment layer count	Each adjustment layer re-runs its filter on every render. Consider Flatten when an edit chain stops being editable.

On low-power devices, lock screen orientation to landscape in iOS Safari (or Android Chrome). The frequent re-layouts triggered by orientation changes are themselves expensive on weak GPUs.

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