Gaze position
=============

[GazeFeatures](/argaze/#argaze.GazeFeatures) defines a [GazePosition](/argaze/#argaze.GazeFeatures.GazePosition) class to handle point coordinates with a precision value.

``` python
from argaze import GazeFeatures

# Define a basic gaze position
gaze_position = GazeFeatures.GazePosition((123, 456))

# Define a gaze position with a precision value
gaze_position = GazeFeatures.GazePosition((789, 765), precision=10)

# Access to gaze position value and precision
print(f'position: {gaze_position.value}')
print(f'precision: {gaze_position.precision}')

```

## Validity

[GazeFeatures](/argaze/#argaze.GazeFeatures) defines also a [UnvalidGazePosition](/argaze/#argaze.GazeFeatures.UnvalidGazePosition) class that inherits from [GazePosition](/argaze/#argaze.GazeFeatures.GazePosition) to handle case where no gaze position exists because of any specific device reason.

``` python
from argaze import GazeFeatures

# Define a basic unvalid gaze position
gaze_position = GazeFeatures.UnvalidGazePosition()

# Define a basic unvalid gaze position with a message value
gaze_position = GazeFeatures.UnvalidGazePosition("Something bad happened")

# Access to gaze position validity
print(f'validity: {gaze_position.valid}')

```

## Distance

[GazePosition](/argaze/#argaze.GazeFeatures.GazePosition) class provides a **distance** method to calculate the distance to another gaze position instance.

![Distance](../../img/distance.png)

``` python
# Distance between A and B positions
d = gaze_position_A.distance(gaze_position_B)
``` 

## Overlapping

[GazePosition](/argaze/#argaze.GazeFeatures.GazePosition) class provides an **overlap** method to test if a gaze position overlaps another one considering their precisions.

![Gaze overlapping](../../img/overlapping.png)

``` python
# Check that A overlaps B
if gaze_position_A.overlap(gaze_position_B): 

        # Do something if A overlaps B
        ...

# Check that A overlaps B and B overlaps A
if gaze_position_A.overlap(gaze_position_B, both=True): 

        # Do something if A overlaps B AND B overlaps A
        ...
```