INFO: Ginga marker parameters

This is part of a larger effort to collect what parameters do different backends take for markers. I was tasked with Ginga and chose to document my findings as GitHub issue. Luckily Ginga has a way for me to programmatically query such things, for example:

https://github.com/ejeschke/ginga/blob/61e44c23d5210cc953bffec7a0fd488727b17dbf/ginga/canvas/types/basic.py#L36

```python
from ginga.canvas.types import basic

params = basic.TextP.get_params_metadata()
for p in params:
print(f"{p.name} | {p.default} | {p.description}")
```

I did not include canvas objects that don't look like they quality as "markers," e.g., Bezier Curve.

### Point

| Name | Default | Description |
| --- | --- | --- |
| coord | data | Set type of coordinates |
| x | 0.0 | X coordinate of center of object |
| y | 0.0 | Y coordinate of center of object |
| radius | 1.0 | Radius of object |
| style | cross | Style of point (default 'cross') |
| linewidth | 1 | Width of outline |
| linestyle | solid | Style of outline (default solid) |
| color | yellow | Color of outline |
| alpha | 1.0 | Opacity of outline |
| showcap | False | Show caps for this object |

### Crosshair

| Name | Default | Description |
| --- | --- | --- |
| coord | data | Set type of coordinates |
| x | 0.0 | X coordinate of center of object |
| y | 0.0 | Y coordinate of center of object |
| linewidth | 1 | Width of outline |
| linestyle | solid | Style of outline (default solid) |
| color | green | Color of outline |
| alpha | 1.0 | Opacity of outline |
| text | None | Text annotation |
| textcolor | yellow | Color of text annotation |
| font | Sans Serif | Font family for text |
| fontsize | None | Font size of text (default: vary by scale) |
| fontscale | True | Scale font with scale of viewer |
| format | xy | Format for text annotation (default: xy) |

### Box (rectangular)

| Name | Default | Description |
| --- | --- | --- |
| coord | data | Set type of coordinates |
| x | 0.0 | X coordinate of center of object |
| y | 0.0 | Y coordinate of center of object |
| xradius | 1.0 | X radius of object |
| yradius | 1.0 | Y radius of object |
| linewidth | 1 | Width of outline |
| linestyle | solid | Style of outline (default solid) |
| color | yellow | Color of outline |
| alpha | 1.0 | Opacity of outline |
| fill | False | Fill the interior |
| fillcolor | None | Color of fill |
| fillalpha | 1.0 | Opacity of fill |
| showcap | False | Show caps for this object |
| rot_deg | 0.0 | Rotation about center of object |

### SquareBox

| Name | Default | Description |
| --- | --- | --- |
| coord | data | Set type of coordinates |
| x | 0.0 | X coordinate of center of object |
| y | 0.0 | Y coordinate of center of object |
| radius | 1.0 | radius of object |
| linewidth | 1 | Width of outline |
| linestyle | solid | Style of outline (default solid) |
| color | yellow | Color of outline |
| alpha | 1.0 | Opacity of outline |
| fill | False | Fill the interior |
| fillcolor | None | Color of fill |
| fillalpha | 1.0 | Opacity of fill |
| showcap | False | Show caps for this object |
| rot_deg | 0.0 | Rotation about center of object |

### Rectangle

The `Square` class somehow is a direct subclass, so has these same parameters.

| Name | Default | Description |
| --- | --- | --- |
| coord | data | Set type of coordinates |
| x1 | 0.0 | First X coordinate of object |
| y1 | 0.0 | First Y coordinate of object |
| x2 | 0.0 | Second X coordinate of object |
| y2 | 0.0 | Second Y coordinate of object |
| linewidth | 1 | Width of outline |
| linestyle | solid | Style of outline (default solid) |
| color | yellow | Color of outline |
| alpha | 1.0 | Opacity of outline |
| fill | False | Fill the interior |
| fillcolor | None | Color of fill |
| fillalpha | 1.0 | Opacity of fill |
| drawdims | False | Annotate with dimensions of object |
| font | Sans Serif | Font family for text |
| showcap | False | Show caps for this object |

### Triangle

| Name | Default | Description |
| --- | --- | --- |
| coord | data | Set type of coordinates |
| x | 0.0 | X coordinate of center of object |
| y | 0.0 | Y coordinate of center of object |
| xradius | 1.0 | X radius of object |
| yradius | 1.0 | Y radius of object |
| linewidth | 1 | Width of outline |
| linestyle | solid | Style of outline (default solid) |
| color | yellow | Color of outline |
| alpha | 1.0 | Opacity of outline |
| fill | False | Fill the interior |
| fillcolor | None | Color of fill |
| fillalpha | 1.0 | Opacity of fill |
| showcap | False | Show caps for this object |
| rot_deg | 0.0 | Rotation about center of object |

### RightTriangle

| Name | Default | Description |
| --- | --- | --- |
| coord | data | Set type of coordinates |
| x1 | 0.0 | First X coordinate of object |
| y1 | 0.0 | First Y coordinate of object |
| x2 | 0.0 | Second X coordinate of object |
| y2 | 0.0 | Second Y coordinate of object |
| linewidth | 1 | Width of outline |
| linestyle | solid | Style of outline (default solid) |
| color | yellow | Color of outline |
| alpha | 1.0 | Opacity of outline |
| fill | False | Fill the interior |
| fillcolor | None | Color of fill |
| fillalpha | 1.0 | Opacity of fill |
| showcap | False | Show caps for this object |

### Circle

| Name | Default | Description |
| --- | --- | --- |
| coord | data | Set type of coordinates |
| x | 0.0 | X coordinate of center of object |
| y | 0.0 | Y coordinate of center of object |
| radius | 1.0 | Radius of object |
| linewidth | 1 | Width of outline |
| linestyle | solid | Style of outline (default solid) |
| color | yellow | Color of outline |
| alpha | 1.0 | Opacity of outline |
| fill | False | Fill the interior |
| fillcolor | None | Color of fill |
| fillalpha | 1.0 | Opacity of fill |
| showcap | False | Show caps for this object |

### Ellipse

| Name | Default | Description |
| --- | --- | --- |
| coord | data | Set type of coordinates |
| x | 0.0 | X coordinate of center of object |
| y | 0.0 | Y coordinate of center of object |
| xradius | 1.0 | X radius of object |
| yradius | 1.0 | Y radius of object |
| linewidth | 1 | Width of outline |
| linestyle | solid | Style of outline (default solid) |
| color | yellow | Color of outline |
| alpha | 1.0 | Opacity of outline |
| fill | False | Fill the interior |
| fillcolor | None | Color of fill |
| fillalpha | 1.0 | Opacity of fill |
| showcap | False | Show caps for this object |
| rot_deg | 0.0 | Rotation about center of object |

### Annulus

| Name | Default | Description |
| --- | --- | --- |
| coord | data | Set type of coordinates |
| x | 0.0 | X coordinate of center of object |
| y | 0.0 | Y coordinate of center of object |
| radius | 1.0 | Inner radius of annulus |
| width | None | Width of annulus |
| atype | circle | Type of annulus |
| linewidth | 1 | Width of outline |
| linestyle | solid | Style of outline (default solid) |
| color | yellow | Color of outline |
| alpha | 1.0 | Opacity of outline |

### Polygon

| Name | Default | Description |
| --- | --- | --- |
| coord | data | Set type of coordinates |
| linewidth | 1 | Width of outline |
| linestyle | solid | Style of outline (default solid) |
| color | yellow | Color of outline |
| alpha | 1.0 | Opacity of outline |
| fill | False | Fill the interior |
| fillcolor | None | Color of fill |
| fillalpha | 1.0 | Opacity of fill |
| showcap | False | Show caps for this object |

### Line

| Name | Default | Description |
| --- | --- | --- |
| coord | data | Set type of coordinates |
| x1 | 0.0 | First X coordinate of object |
| y1 | 0.0 | First Y coordinate of object |
| x2 | 0.0 | Second X coordinate of object |
| y2 | 0.0 | Second Y coordinate of object |
| linewidth | 1 | Width of outline |
| linestyle | solid | Style of outline (default solid) |
| arrow | none | Arrows at ends (default: none) |
| color | yellow | Color of outline |
| alpha | 1.0 | Opacity of outline |
| showcap | False | Show caps for this object |

### Text

| Name | Default | Description |
| --- | --- | --- |
| coord | data | Set type of coordinates |
| x | 0.0 | X coordinate of lower left of text |
| y | 0.0 | Y coordinate of lower left of text |
| text | EDIT ME | Text to display |
| font | Sans Serif | Font family for text |
| fontsize | None | Font size of text (default: vary by scale) |
| fontsize_min | 6.0 | Minimum font size of text (if not fixed) |
| fontsize_max | None | Maximum font size of text (if not fixed) |
| fontscale | False | Scale font with scale of viewer |
| color | yellow | Color of text |
| alpha | 1.0 | Opacity of text |
| rot_deg | 0.0 | Rotation of text |
| showcap | False | Show caps for this object |

Start with the linked Ginga entry point, ginga/canvas/types/basic.py, and review how get_params_metadata() exposes marker parameters. The issue does not name a destination file, test, or concrete repository change, so confirm where these findings belong before defining completion.

Written by the indexing model from the issue text.