grid with standard page size guides

[herrsimon]

When using Lorien for teaching, notes are commonly exported and then distributed as pdf (which in turn are often printed by students). While converting from svg to pdf is of course trivially possible outside of Lorien (and should also remain outside for simplicity), it would be nice to support grids indicating common papersizes, such as A4 or letter. These size guides could be indicated via slightly bolder lines on top of the existing grid.

[hansemro]

Great idea! Would something like customizable major and minor grid lines help in this case? Prefer having presets for common paper sizes? Or both?

Quick example:

major_minor.mp4

[hansemro]

Test branch: https://github.com/hansemro/Lorien/commits/major-minor-grid

[herrsimon]

Thanks a lot for the rapid prototyping, it looks exactly as I imagined it!

I think that separately configurable major and minor grid lines are reasonable, with the major grid representing some natural boundaries (virtual page sizes) and the minor grid acting as a guide for drawing. Consequently, the user should also be able to manually specify the size of these major guidelines (in addition to predefined standard sizes like A4).

However, thinking about it further, this feature is probably not as trivial to implement as it looks like as one has to take into account the fact that pixels are dimensionless. For viewing an accurate A4 guid, one would need to obtain the current screen's dpi value, so that at zoom level 1 one guide will always cover an area of 210 mm x 297 mm on the screen. Also, at first save the dpi - in the form of assigning some physical distance between two pixels - needs to be stored so that the guides are truly useful (think about reopening a dimensionless file on a screen with a different dpi).

I didn't look at Lorien's code yet and unfortunately also don't know enough about the svg format in order to make useful remarks. Let me know in case you want me to investigate how to solve this standard problem properly and I will look at implementations of tools like inkscape on the coming weekend.

[mbrlabs]

I thought about it for a while and i generally like the idea. But i don't think it has to be that complicated...vector graphics are basically indefinitely scalabe, so in the end it's just about the witdh/height ratio. Making it dependent on the dpi is overkill in my opinion (i'm especially opposed to saving this kind of information in the .lorien file). All it should be is a visual aid (like the squared grid is right now). Also what would happen if you have a 2-monitor setup with different screen resolutions? You just have to zoom in/out depending on your screen resolution when you share .lorien files with other people or work on differenty sized monitors. And you only have to do this once anyway. The exported svg will then always have the correct ratio and you can scale it up/down and render it in any program that supports svg ;)

Oh and the default brush size compared to the A4 grid should by default be sized in a way so that it feels like writing on a real A4 paper. This can be done independent of the screen size.

I also have some ideas for different kinds of grids that can be enabled/disabled at the same time in the settings:

• basic squared grid like right now
• dotted grid (looks even better than squared IMO)
• ISO norms (this proposal)

[herrsimon]

First of all, sorry for the late reply.

I thought about it for a while and i generally like the idea. But i don't think it has to be that complicated...vector graphics are basically indefinitely scalabe, so in the end it's just about the witdh/height ratio. Making it dependent on the dpi is overkill in my opinion (i'm especially opposed to saving this kind of information in the .lorien file). All it should be is a visual aid (like the squared grid is right now).

I'm all ears for keeping things simple, that's the main reason I started using lorien! However, at the moment I don't completely understand what you're actually proposing. Of course vector graphics are essentially dimensionless, but at some point you have to apply some dimension (i.e. say how many pixels a svg coordinate unit/grid rectangle side should map to). Are you intending to make the grid separately zoomable, possibly with some history function so that lorien remembers the last used mapping? Even this would not retain all information needed to properly recover the correct grid sizing (see below).

Also what would happen if you have a 2-monitor setup with different screen resolutions? You just have to zoom in/out depending on your screen resolution when you share .lorien files with other people or work on differenty sized monitors.

That's a valid point I didn't consider.

And you only have to do this once anyway. The exported svg will then always have the correct ratio and you can scale it up/down and render it in any program that supports svg ;)

How are you obtaining the correct dimensions if you only know the ratio? Say you want to draw on a single A4 page and fill an area in the upper left of the virtual page (as given by a grid), which can be captured in a rectangle with the same ratio as the page. If you export this drawing to svg, there is no way to recover the free area anymore, or am I wrong? In other words, you then have to decide if you print this upper left part scaled to a full A4 page, just half a page or any other fraction of the page. Maybe it's my lack of understanding of the svg format, I'm assuming that just the coordinates of existing points are saved, respective to some origin (in the upper left?). However, a way out could be to optionally embed (the four corner pixels of) all grid cells which contain some points into the svg when exporting.

Oh and the default brush size compared to the A4 grid should by default be sized in a way so that it feels like writing on a real A4 paper. This can be done independent of the screen size.

That's a very good idea.

I also have some ideas for different kinds of grids that can be enabled/disabled at the same time in the settings:

• basic squared grid like right now
• dotted grid (looks even better than squared IMO)
• ISO norms (this proposal)

Completely agree to this! Dotted grid is my favorite both virtually and on physical paper.