[Qgis-user] Ideas for QGIS plugin?

[Martin Dobias]

On Tue, Feb 3, 2009 at 10:33 PM,  <pcreso at pcreso.com> wrote:
> Is it possible to have a second transparent map canvas, analogous to the Mapinfo cosmetic layer.
>
> This would allow, for example, a complex background map to remain static so a gps layer in the new canvas can be quickly refreshed without refreshing the entire map & all the background layers, unless, of couser, the map extent changes.
>
> There are several times I've made simple changes to a small layer & QGIS takes some time to re-render everything, when 99% of the refresh doesn't actually change anything.
>
> This could be accomplished by having two map canvases, so users could add static layers to the bottom one & more dynamic ones to the top one, to suit their needs.

This is already possible. But instead of cosmetic layer we talk about
canvas items: map canvas contains rendered map and optionally any
number of other map canvas items (see QgsMapCanvasItem class). Canvas
items can be updated whenever needed and no re-render of map is
required. Also rubber band (see QgsRubberBand) which is used for
measuring distances and areas is a canvas item.

Martin