This is an excellent start. Do you need the grid? If yes, then I can add this to Roassal. It is easy to define an interaction that define a grid.
I have added event to signal the beginning and ending of a dragging-and-dropping. Here is an example: -=-=-=-=-=-=-=-= | v e | v := RTView new. e := (RTEllipse new size: 30) element. e @ RTDraggable. v add: e. e when: TRMouseDragStart do: [ :evt | Transcript show: evt printString; cr. evt element trachelShape color: Color red. v signalUpdate ]. e when: TRMouseDragEnd do: [ :evt | Transcript show: evt printString; cr ]. v open -=-=-=-=-=-=-=-= Let me know whether this helps. Cheers, Alexandre -- _,.;:~^~:;._,.;:~^~:;._,.;:~^~:;._,.;:~^~:;._,.;: Alexandre Bergel http://www.bergel.eu ^~:;._,.;:~^~:;._,.;:~^~:;._,.;:~^~:;._,.;:~^~:;. On Aug 1, 2014, at 2:36 PM, Peter Uhnák <i.uh...@gmail.com> wrote: > Hi Alex, > > While the "snap to grid" might be complicated I thought of simpler solution > that might be achievable purely at Roassal level without the need to change > Trachel classes. You can look at Umlet, since I am trying to copy it's grid > behavior here. > Basically you don't move objects with mouse immediately but only after fixed > increments. However I've encountered a problem with TRMouseDragging>>step, > since I would probably need to continuously sum the individual steps and then > reset them when dragging has started. > > Here is a _very_ crude prototype: > --------------------- > "i subclassed RTDraggable and changed initializeElement: method as follows" > initializeElement: element > | sum gridSize | > gridSize := 20. > sum := 0 @ 0. > element > when: TRMouseDragging > do: [ :e | > | d t | > t := RTGroup withAll: groupToDrag. > (t includes: element) > ifFalse: [ t add: element ]. > d := element view canvas camera > distanceFromPixelToSpace: e step. > sum := sum + d. > "move element only in increments of gridSize" > d := gridSize * ((sum x / gridSize) truncated @ (sum y > / gridSize) truncated). > sum := sum - d. > t translateBy: d. > e signalUpdate ] > --------------------- > > and here is a demo utilizing it > > ----------------------------- > | v e1 e2 line gridSize b1 b2 b3 b4 edge | > v := RTView new. > > "draw grid" > gridSize := 20. > > (-20 to: 20) do: [ :i | > b1 := RTBox element. > b2 := RTBox element. > b3 := RTBox element. > b4 := RTBox element. > b1 translateTo: (i * gridSize) @ -1000. "top side" > b2 translateTo: (i * gridSize) @ 1000. "bottom side" > b3 translateTo: -1000 @ (i * gridSize). "left side" > b4 translateTo: 1000 @ (i * gridSize). "right side" > "vertical line" > edge := RTLine edgeFrom: b1 to: b2. > v add: edge. > "horizontal line" > edge := RTLine edgeFrom: b3 to: b4. > v add: edge. > ]. > > e1 := (RTEllipse new size: 30; color: Color magenta) element. > e1 translateTo: -20 @ 0. > e1 @ RGGridDraggable. > > e2 := (RTEllipse new size: 30; color: Color magenta) element. > e2 translateTo: 20 @ 0. > e2 @ RGGridDraggable. > > (line := RTLine edgeFrom: e1 to: e2) shape color:Color black. > > v add: e1; add: e2; add: line. > > v open. > ----------------------------- > > Obviously it needs a lot of fine-tuning and such. Since RTInteraction > (RTDraggable) instances are not created directly the gridSize would have to > be stored probably class side. Also there is a problem with resetting the > "sum" variable when dragging starts. (There is no TRMouseDragStart event as > far as I've seen). And also drawing the grid itself the way I've done is very > brutal and doesn't really work if I want to move the canvas camera (perhaps > image pattern as a background would work better). > > What are your thoughts on this? > > Peter > > > > > On Fri, Aug 1, 2014 at 4:07 PM, Alexandre Bergel <alexandre.ber...@me.com> > wrote: > Hi Peter! > > > While playing with RTMultiLine I thought that it would be nice to have > > option for RTDraggable elements to snap to a grid / move only by fixed > > increments - for example the position could only be divisible by 10 (grid > > size would be 10), so dragging from 20@10 to 26@4 would jump to 30@0. Is > > something like this possible with current implementation? > > > I first thought this would be easy. But actually it is not. > The way to achieve the snap on grid behavior is to have an indirection in the > Trachel classes. Each trachel shape knows its position (the position is > contained in the matrix attached to each shape). The snap-on-grid means you > need to slightly process the matrix coordinate. Maybe there are other way to > do this, but it does not look like. Changing Trachel because of this seems a > bit overkill... > > Cheers, > Alexandre > -- > _,.;:~^~:;._,.;:~^~:;._,.;:~^~:;._,.;:~^~:;._,.;: > Alexandre Bergel http://www.bergel.eu > ^~:;._,.;:~^~:;._,.;:~^~:;._,.;:~^~:;._,.;:~^~:;. > > > > On Jul 31, 2014, at 3:58 PM, Peter Uhnák <i.uh...@gmail.com> wrote: > > > While playing with RTMultiLine I thought that it would be nice to have > > option for RTDraggable elements to snap to a grid / move only by fixed > > increments - for example the position could only be divisible by 10 (grid > > size would be 10), so dragging from 20@10 to 26@4 would jump to 30@0. Is > > something like this possible with current implementation? > > > > The second question is: is it possible for element to subscribe for > > position updates of another element? (I.e. element A watches for movement > > of element B and moves accordingly). I know I could add both of them to a > > composite shape or RTGroup (RTDraggable>>groupToDrag:), however I would > > prefer something more loosely coupled. > > > > In RTDraggable>>initializeElement: i found > > " element when: TRMouseDragging do: [ :e | e element translateBy: e > > step. e signalUpdate ]" > > however it is commented out so perhaps there some other way? > > > > Peter > > >
