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Canvas size and zoom

A MultiTaction Canvus canvas is a working area with a fixed size in canvas pixels. You pan and zoom over it, and Canvus keeps the view inside its edges. The size is a setting, not a hard ceiling: if you need more room, give new canvases a larger size.

Default canvas size

When Canvus Client creates a new canvas, the canvas is 9600 px wide. Canvus works out the height from the shape of the workspace the canvas first opens in, so the canvas has the same proportions as your screen or wall:

Workspace Canvas size with the default setting
16:9 display, for example 3840 x 2160 px 9600 x 5400 px
32:9 wall, for example 7680 x 2160 px 9600 x 2700 px
Portrait 9:16 display 5400 x 9600 px

On a portrait workspace the 9600 px applies to the height, which is the longer side.

Canvases created through the REST API, including canvases created with New canvas in the Canvus Server web UI, use a different default. When no size is given, the canvas is 9600 x 5400 px. The REST API rejects sizes smaller than 1200 x 800 px. See the canvases endpoint in the developer guide.

Canvas size, zoom and memory

In everyday use you do not need to manage the resolution of a canvas. Zoom sets the context: zoom in to work on detail, zoom out to see the whole. Anchors act as pages at a chosen zoom level inside one canvas, and you can nest them, so a main theme can have its own anchors for the zoomed-in parts of it. Canvus scales what you see to the resolution of your wall.

Canvus renders only the pixels that are on screen. Its memory use follows the native resolution of your wall, not the size of the canvas, so a larger canvas does not by itself need more memory or graphics memory.

Change the size of new canvases

Set size in the [canvas] section of mt-canvus.ini. You can also change it on the settings page under the canvas settings.

[canvas]
; Size of new canvases in canvas pixels.
; One number sets the longer edge; the other edge follows the workspace shape.
; Two numbers set the width and the height.
; DEFAULT: 9600
; size=9600
; size=19200 10800
  • One number, for example size=19200, sets the longer edge. Canvus derives the other edge from the workspace, as described above.
  • Two numbers separated by a space, for example size=19200 10800, set the width and the height exactly.
  • Canvus does not enforce an upper limit.
  • If the value cannot be read, Canvus logs a warning and uses 9600.

The setting applies only to canvases created after the change. An existing canvas keeps the size it was created with.

Give large walls a larger canvas

The canvas size is measured in the same pixels as your workspace. A wall that is 11520 px wide is already wider than the default 9600 px canvas, so when you zoom all the way out the whole canvas covers the wall and you cannot zoom out any further. For a wide or high-resolution wall, set size to several times the wall width so people have room to spread content out.

Zoom limits

  • Zooming in stops at 10x: one canvas pixel then covers 10 pixels of the workspace. The same limit applies when Canvus zooms to an item for you, for example with Fit to screen.
  • Zooming out stops when the whole canvas is visible. Canvus compares the canvas with the workspace in both directions and stops when the canvas fits in both, so one pair of canvas edges touches the workspace edges. If you pinch further, the canvas springs back.
  • Panning stops at the edges of the canvas. When the canvas is larger than the view, Canvus moves it back so that no empty space shows beyond an edge.

Because of these limits, the shape of the canvas and the shape of the wall together decide how far out you can zoom. A canvas with the same proportions as the wall fills the wall exactly at the furthest zoom. A canvas with different proportions leaves empty space beside it in one direction at the furthest zoom.

During a presentation the limits are lifted, so a slide can frame any area of the canvas. They return when the presentation ends.

Pan and zoom

  • Touch. Drag an empty part of the canvas to pan. Pinch with two or more fingers to zoom.
  • Mouse. Drag an empty part of the canvas to pan. Use the mouse wheel over an empty part of the canvas to zoom. In pen or eraser mode the wheel changes the pen line width instead.
  • Pin the canvas. Open the main menu and tap Pin canvas to stop the canvas from moving or zooming. Tap it again to unpin. See Pinning content.
  • Fit to screen. Open the main menu and tap Fit to screen. Canvus zooms so that all the items on the canvas fill about 90% of the view.

The view when a canvas opens

These [canvas] settings decide where the view starts when a canvas opens. See Configure default pin and display settings.

  • anchor-viewport=true moves the view to the first anchor. See Anchors and zones.
  • zoom-viewport=true zooms so that all items are visible, as Fit to screen does. Canvus uses it when anchor-viewport is off or the canvas has no anchors.
  • pin-canvas=true pins the canvas when it opens.
  • auto-pin-after pins the canvas after it has not been moved or zoomed for the given number of seconds.