Function nextZoomLevel

background_scripts/main.js:210–236

(currentZoom, steps)

}

function nextZoomLevel(currentZoom, steps) {
  // Chrome's default zoom levels.
  const chromeLevels = [0.25, 0.33, 0.5, 0.75, 0.8, 0.9, 1, 1.1, 1.25, 1.5, 1.75, 2, 2.5, 3, 4, 5];
  // Firefox's default zoom levels.
  const firefoxLevels = [0.3, 0.5, 0.67, 0.8, 0.9, 1, 1.1, 1.2, 1.33, 1.5, 1.7, 2, 2.4, 3, 4, 5];

  let zoomLevels = chromeLevels; // Chrome by default
  if (bgUtils.isFirefox()) {
    zoomLevels = firefoxLevels;
  }

  if (steps === 0) { // Nothing
    return currentZoom;
  } else if (steps > 0) { // In
    // Chrome sometimes returns values with floating point errors.
    // Example: Chrome gives 0.32999999999999996 instead of 0.33.
    currentZoom += 0.0000001; // This is needed to solve floating point bugs in Chrome.
    const nextIndex = zoomLevels.findIndex((level) => level > currentZoom);
    const floorIndex = nextIndex == -1 ? zoomLevels.length : nextIndex - 1;
    return zoomLevels[Math.min(zoomLevels.length - 1, floorIndex + steps)];
  } else if (steps < 0) { // Out
    currentZoom -= 0.0000001; // This is needed to solve floating point bugs in Chrome.
    let ceilIndex = zoomLevels.findIndex((level) => level >= currentZoom);
    ceilIndex = ceilIndex == -1 ? zoomLevels.length : ceilIndex;
    return zoomLevels[Math.max(0, ceilIndex + steps)];
  }
}

// These are commands which are bound to keystrokes which must be handled by the background page.
// They are mapped in commands.js.