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-------- Forwarded Message -------- Subject: Re: [Qgis-developer] Memory Layers - some proposals Date: Thu, 25 Sep 2014 06:04:19 -0800 From: Gary Sherman <gsher...@geoapt.com> Organization: GeoApt LLC To: Matthias Kuhn <matthias.k...@gmx.ch> CC: gsher...@geoapt.com On 9/25/14 1:10 AM, Matthias Kuhn wrote:
Aren't there two different possibilities in which such layers can be used: * As a scratch layer for the user, which he may want to save in the end * As a means for plugins to show information to the user In the first scenario, the user may actually want to save the information because he realized in the process of drawing it, that it's valuable to him (if he would have known from the beginning, he could have started with a permanent layer type). In this case it would be nice to make the user aware of the risk of loosing data and offer him a simple way to save it (to an OGR supported format). In the second scenario, the information may be completely reproducible by the plugin or the information drawn by the user intercepted by the plugin and redirected to suitable places. In such a scenario a "Do you want to permanently save?" dialog would not be appropriate. And therefore there should be a possibility to disable it.
I agree---I have a plugin that uses memory layers to display information abstracted from a database (with no QGIS data provider). This functionality is essential and should not be changed, rather additional features added to support interactive use through the UI.
On the other hand, I also tend to use my /tmp folder on my machine for data I use to play around for the next couple of minutes but that I am completely aware of that it can be lost anytime (and I don't want my computer to ask me: "Hey, you have saved that download to /tmp and I'm going to delete it now, is that ok for you?"). So I tend to disagree with Sandros "why would you want to loose the data?" and answer it with "because it's intermediate, volatile and/or temporary." All in all: there are two scenarios, one with manual operation, one with plugins. The second one needs to be controlled by python, the first one is about awareness. This awareness can be achieved by one or more of the following * Icons * Message bar (e.g. when starting to digitize "You are digitizing on a temporary layer. Do you want to convert it to a permanent layer? Click here.") * Message box when removing the layer from the canvas/closing the app "There is unsaved information, you will loose it unless you donate 5$ to the QGIS project. Click here" Or did I get this wrong? Matthias _______________________________________________ Qgis-developer mailing list Qgis-developer@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/qgis-developer
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