Reader Device Profiles

Valpr Reader features a Device Profiles engine. Unlike conventional readers where typography and layout settings are global, profiles allow you to switch instantly between optimized configurations calibrated for different physical screens, viewing distances, and input ergonomics.

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Built-In Default Profiles

Valpr Reader ships with five profiles: four hardware profiles plus a doom-scroll mode variant. The hardware profiles are intentionally separate because display physics, viewing distance, and ergonomic grip differ fundamentally across device classes:

Profile	ID	Font Size	Line Height	Columns	Margin	Key Differences
PC / Desktop	default-desktop	20px	1.65	Auto (0)	16px	Mouse/keyboard navigation, no tap-edge paging, wake lock off
Mobile / Phone	default-mobile	17px	1.55	1	16px	Closest viewing distance, smaller font, 15px swipe threshold, wake lock on
Mobile / Doom Scroll	default-mobile-scroll	17px	1.60	1	16px	Continuous vertical scroll (horizontal-tb), no tap-edge paging, wake lock on
Tablet	default-tablet	22px	1.70	1	24px	High-DPI LCD, wider 24px thumb bezel margin, wake lock on, 900px column ceiling
E-Reader / E-Ink	default-ereader	20px	1.60	1	10px	E-Ink contrast boost (font weight 500), 20px swipe threshold, forced light theme, pinned header, no tap edge, no mid-sentence breaks

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Engineering & Physical Rationale

Every default value in the profile matrix is mathematically calibrated to device physics:

1. Font Size Hierarchy (Mobile 17px < Desktop 20px = E-Reader 20px < Tablet 22px)

• Phone (~25 cm viewing distance): Handheld close to the face. 17px provides high information density without causing eye strain.
• Desktop (~60–75 cm viewing distance): Fixed monitor distance. 20px ensures kanji radicals remain distinct without leaning forward.
• Tablet (~45 cm viewing distance): Tablets are held further away than phones or placed in lap stands. 22px accommodates the wider visual angle.
• E-Reader (~30–40 cm viewing distance): 20px strikes the ideal balance for 300 DPI E-Ink screens.

2. Font Weight 500 on E-Reader (Stroke Boost)

Standard LCD displays boast contrast ratios exceeding 1000:1 with high-brightness backlights. In contrast, reflective E-Ink Carta panels provide around 15:1 contrast.

• Standard regular font weight (400) can appear thin or washed out under ambient light.
• Setting fontWeight: 500 (Medium) injects extra stroke weight into complex kanji characters, preserving clarity and legibility without needing to crank up battery-draining front lights.

3. Vertical Font Kerning (vkrn) Enabled on All Profiles

Japanese fonts such as Noto Serif JP, Noto Sans JP, and Shippori Mincho contain dedicated OpenType vkrn tables. Modern rendering engines apply these kerning metrics at near-zero CPU cost. This tightens uneven spacing around brackets (「」), full-width punctuation (、, 。), and quotation marks in vertical text.

4. Display Wake Lock on Mobile & Tablet

Reading an intensive page of Japanese literature (300–500 characters plus multiple dictionary lookups) routinely takes 45 to 90 seconds—exceeding the standard 30-second mobile OS screen sleep timer.

• Wake lock is enabled on Mobile and Tablet to prevent screen dimming while reading.
• Wake lock is disabled on Desktop where native OS sleep timers are much longer.

5. Swipe Threshold: 15px vs. 20px

• Mobile & Tablet (15px): 60Hz/120Hz capacitive touchscreens respond instantly, so a nimble 15px swipe threshold feels natural.
• E-Reader (20px): Low-refresh E-Ink panels (~10–15 Hz) exhibit ghosting artifacts during dragging gestures. A higher 20px threshold forces deliberate swipes rather than accidental micro-drags.

6. Margins: Tablet (24px) vs. E-Reader (10px)

• Tablets: Modern slim-bezel tablets leave almost no physical frame for your thumbs. The 24px digital margin prevents thumbs from covering text.
• E-Readers: Devices like Kindle, Kobo, and Boox already feature wide physical plastic bezels. A tight 10px margin maximizes usable screen real estate.

7. Column Height Limit (900px on Tablet)

Without a constraint, full-screen vertical text on a 12.9" tablet would result in lines exceeding 60–70 characters. The secondDimensionMaxValue: 900px setting caps column height to approximately 42 characters, faithfully matching the standard line length of traditional Japanese bunkobon (文庫本) paperbacks.

8. Pinned Header, No Tap Edge, No Mid-Sentence Breaks (E-Reader)

• Pinned header (keepReaderHeaderVisible: true): The auto-hiding top bar floats over the first lines of text, which is especially disruptive on slow-refreshing E-Ink. Pinning keeps the bar permanently visible in its own reserved space so it never overlaps the text. Every full-screen refresh on E-Ink costs a visible flash; a stable header avoids re-compositing surprises. Available per-profile under Settings > Reader > Navigation & Gestures > Keep Reader Header Visible.
• Tap edge off (enableTapEdgeToFlip: false): E-Readers ship with physical page-turn buttons, so the screen-edge tap zones only steal margin space and cause accidental turns.
• Mid-sentence breaks avoided (avoidPageBreak: true): Page turns on E-Ink are expensive full refreshes, so each page should end at a clean sentence boundary rather than stranding half a sentence.

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Managing Profiles

Selecting an Active Profile

1. Navigate to Settings > Reader > Profiles.
2. Click on any profile card to activate it immediately.
3. The reader interface and all reader windows will re-render with the new profile's typography, margins, and controls.

Creating a Custom Profile

1. In the Profiles section, click + New Profile.
2. Choose a starting template (Desktop, Mobile, Doom Scroll, Tablet, or E-Reader).
3. Name your profile and pick an icon.
4. Adjust font size, line height, margins, and custom CSS as desired.

Profile Roaming & Cloud Sync

When cloud synchronization is enabled (Google Drive or OneDrive), custom profiles roam across your devices. You can read on your desktop using your tuned default-desktop configuration and pick up seamlessly on your mobile phone with default-mobile.