# Constants
## Type Aliases
``` python
# Test CardRole type
role: CardRole = "focused"
assert role == "focused"
role = "context"
assert role == "context"
print("CardRole type alias tests passed!")
```
CardRole type alias tests passed!
## Scroll Navigation Constants
Thresholds for converting mouse wheel events into card navigation.
``` python
assert SCROLL_THRESHOLD == 1
assert NAVIGATION_COOLDOWN == 100
assert TRACKPAD_COOLDOWN == 250
print("Scroll constants tests passed!")
```
Scroll constants tests passed!
## Touch Navigation Constants
Thresholds for converting touch gestures into card navigation and scale
adjustments. Touch-and-drag uses the focused slot height as the step
distance; these constants govern the simple-swipe fallback, momentum
decay after a fast swipe, and pinch-to-zoom sensitivity.
``` python
assert TOUCH_SWIPE_THRESHOLD == 30
assert TOUCH_MOMENTUM_MIN_VELOCITY == 0.5
assert TOUCH_MOMENTUM_FRICTION == 0.95
assert TOUCH_PINCH_THRESHOLD == 30
assert TOUCH_VELOCITY_SAMPLES == 5
print("Touch constants tests passed!")
```
Touch constants tests passed!
## localStorage Key Patterns
Key templates for persisting viewport preferences to localStorage. The
prefix is interpolated at runtime to support multi-instance.
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source
### auto_count_storage_key
``` python
def auto_count_storage_key(
prefix:str, # Card stack instance prefix
)->str: # localStorage key for auto card count mode
```
*Generate localStorage key for auto card count mode.*
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source
### card_count_storage_key
``` python
def card_count_storage_key(
prefix:str, # Card stack instance prefix
)->str: # localStorage key for card count
```
*Generate localStorage key for card count.*
------------------------------------------------------------------------
source
### scale_storage_key
``` python
def scale_storage_key(
prefix:str, # Card stack instance prefix
)->str: # localStorage key for card scale
```
*Generate localStorage key for card scale.*
------------------------------------------------------------------------
source
### width_storage_key
``` python
def width_storage_key(
prefix:str, # Card stack instance prefix
)->str: # localStorage key for card width
```
*Generate localStorage key for card width.*
``` python
# Test storage key generation
assert width_storage_key("cs0") == "cs0-card-width"
assert scale_storage_key("cs0") == "cs0-card-scale"
assert card_count_storage_key("cs0") == "cs0-card-count"
assert auto_count_storage_key("cs0") == "cs0-card-count-auto"
# Multi-instance keys are unique
assert width_storage_key("text") != width_storage_key("vad")
assert auto_count_storage_key("text") != auto_count_storage_key("vad")
print("Storage key tests passed!")
```
Storage key tests passed!
## Viewport Defaults
``` python
assert DEFAULT_VISIBLE_COUNT == 1
assert DEFAULT_CARD_WIDTH == 80
assert DEFAULT_CARD_SCALE == 100
print("Viewport default tests passed!")
```