Pan and zoom

An elm-ui component that supports dragging and scrolling with the mouse to pan and zoom.

This is a fork from JohanWinther/elm-pan-and-zoom. All the credit goes to the original author. This fork just adapts the view-function to integrate well with elm-ui.

Component

The component constists of a Viewport that contains a "content box":

╔═════════════════════════╗
║                         ║
║    ┌────────────────────║╌╌┐
║    │                    ║  ┊
║    │                    ║  ┊
║    │        content     ║  ┊
║    │                    ║  ┊
║    │                    ║  ┊
╚═════════════════════════╝  ┊
     └╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┘


╔═══╗
║   ║ = viewport
╚═══╝

┌───┐
│   │ = content box
└───┘

Mouse interactions

Panning

The content box can be moved by dragging anywhere in the viewport with the mouse.

x = mouse pointer

╔═════════════════════════╗
║                  x-->   ║
║    ┌─────────┐-->       ║
║    │         │-->       ║
║    │         │-->       ║
║    │         │-->       ║
║    └─────────┘-->       ║
║                         ║
╚═════════════════════════╝
╔═════════════════════════╗
║                      x  ║
║        ┌─────────┐      ║
║        │         │      ║
║        │         │      ║
║        │         │      ║
║        └─────────┘      ║
║                         ║
╚═════════════════════════╝

The content box can also be moved by dragging the box itself.

╔═════════════════════════╗
║                         ║
║    ┌─────────┐----------╫----->
║    │ x-------┼--------> ║
║    │         │----------╫----->
║    │         │----------╫----->
║    └─────────┘----------╫----->
║                         ║
╚═════════════════════════╝
╔═════════════════════════╗
║                         ║
║                      ┌──║╌╌╌╌╌╌┐
║                      │ x║      ┊
║                      │  ║      ┊
║                      │  ║      ┊
║                      └──║╌╌╌╌╌╌┘
║                         ║
╚═════════════════════════╝

Zooming

The content box can be scaled by scrolling the mouse wheel anywhere in the viewport.

╔═════════════════════════╗
║                         ║
║    x─────────┐          ║
║    │         │          ║
║    │         │          ║
║    │         │          ║
║    └─────────┘          ║
║                         ║
╚═════════════════════════╝
╔═════════════════════════╗
║                         ║
║    x────────────────────║───┐
║    │                    ║   ┊
║    │                    ║   ┊
║    │                    ║   ┊
║    │                    ║   ┊
╚═════════════════════════╝   ┊
     ┊                        ┊
     ┊                        ┊
     ┊                        ┊
     └╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┘

When zooming by scrolling content box will always scale relative to the mouse pointer.

╔═════════════════════════╗
║                         ║
║    ┌─────────┐          ║
║    │         │          ║
║    │         │       x  ║
║    │         │          ║
║    └─────────┘          ║
║                         ║
╚═════════════════════════╝
╔═════════════════════════╗
║                         ║
║                         ║
║          ┌────┐         ║
║          │    │      x  ║
║          └────┘         ║
║                         ║
║                         ║
╚═════════════════════════╝

Programmatic interaction

It is possible to programatically apply transformations with