From: Jonathan W. <jw...@ph...> - 2008-04-08 02:29:23
|
Hi Hazen > > Having said that, things are as they are because this is the behaviour > > of the current cairo-based devices. Admittedly a pre-existing drawable > > is different from one created by plplot but even so, consistency can > > sometimes be a good thing. The other thing to bear in mind is that > > "clearing to the background colour" will be the usual operational mode I > > would imagine, so an argument could be raised that the "don't clear" > > behaviour should be an opt-in option - possibly set using a new escape > > function or perhaps via a new "flags" option to the PLXcairoDrawableInfo > > structure. If we went with the latter though, PLXcairoDrawableInfo > > really needs to be made available to applications. Currently there's > > only 2 members - the display and the drawable - and it's not too hard > > for users to hack up their own structure to pass in. However, once we > > go beyond this PLXcairoDrawableInfo really must be publically available > > so users can't get it wrong. > > I'd propose making "clearing to the background color" a driver option > so that we can use it with xcairo, memcairo and extcairo. Yep, that would work nicely. > I think that we should make our decision about the clearing default > consistent across these 3 driver options, but I don't have much > preference about whether or not clearing is the default. > > Doug, any thoughts about having clearing be the default? My own personal view is that clearing should be the default with an option to not clear being available. This is because in most cases one will be drawing a plain plot for data display purposes without needing pre-prepared backgrounds to be preserved. For those cases where a background (or any other previously prepared content) needs to be preserved the option is there to cope with it. I also suspect that newcomers to plplot may well expect the drawable/cairo-context to be cleared by the implicit "beginning of page" operation which happens before the first plot At the end of the day though I could live with either decision so long as it's clearly documented. Regards jonathan |
From: Doug H. <dh...@ma...> - 2008-04-08 15:26:30
|
Hi Hazen: For what I use the memcairo driver for, clearing the memory not not the behavior I want. I want to pass in some memory already containing an image and then plot a graph on top of it. To first generate the image and then have plplot clear it would be disappointing, to say the least! I'd vote for adding an option to clear to the background, but not to make it the default. Regards, Doug dh...@uc... Software Engineer III UCAR - COSMIC, Tel. (303) 497-2611 On Mon, 7 Apr 2008, Hazen Babcock wrote: > On Apr 6, 2008, at 9:17 PM, Jonathan Woithe wrote: >> >> Having said that, things are as they are because this is the behaviour of >> the current cairo-based devices. Admittedly a pre-existing drawable is >> different from one created by plplot but even so, consistency can sometimes >> be a good thing. The other thing to bear in mind is that "clearing to the >> background colour" will be the usual operational mode I would imagine, so >> an >> argument could be raised that the "don't clear" behaviour should be an >> opt-in option - possibly set using a new escape function or perhaps via a >> new "flags" option to the PLXcairoDrawableInfo structure. If we went with >> the latter though, PLXcairoDrawableInfo really needs to be made available >> to applications. Currently there's only 2 members - the display and the >> drawable - and it's not too hard for users to hack up their own structure >> to pass in. However, once we go beyond this PLXcairoDrawableInfo really >> must be publically available so users can't get it wrong. > > I'd propose making "clearing to the background color" a driver option so that > we can use it with xcairo, memcairo and extcairo. > > I think that we should make our decision about the clearing default > consistent across these 3 driver options, but I don't have much preference > about whether or not clearing is the default. > > Doug, any thoughts about having clearing be the default? > > best, > -Hazen |
From: Jonathan W. <jw...@ph...> - 2008-04-08 23:21:58
|
Hi guys > Hi Hazen: For what I use the memcairo driver for, clearing the memory not > not the behavior I want. I want to pass in some memory already containing > an image and then plot a graph on top of it. To first generate the image > and then have plplot clear it would be disappointing, to say the least! For sure - I think there's no question that having pre-plot clearing as an option is the way to go. The real question is what the default should be which IMHO comes down to what would be the most common usage pattern. I may be completely wrong here but I would expect that most people using plplot are plotting data of some kind for analysis and/or publication. In this situation one rarely if ever puts such plots over the top of an image. If the "blank background" case is the most common usage it makes a case for clearing to be the default with an option to turn it off for those who do in fact need to prepare a background prior to plotting. I shall now wait for democracy to take its course. :-) Regards jonathan |