Dragging a shape over the screen

> Does anybody have an idea how to drag a (rectangular) shape over the
> whole screen? I'm using this for a drag & drop feature to indicate the
> object's size and exact drop location.
>
> My current implementation goes like this:
>
>        Screen default
>            displayShape: shape
>            at: InputState default mousePoint - offset
>            forMilliseconds: 100.  
> whereby the shape is initialized with aPointArray. This however
> creates really annoying flicker. How can a shape be dragged smoothly?
>
> Any suggestion is appreciated.
>
> Andre
>
>
>

> Sorry for the noise. I just discovered one possible solution myself  
> (see code below).
>
> MyDragDropManager is a subclass of DragDropManager extended by an  
> instance variable bearing the dragged shape. After the drop, the  
> flag "dragging" is reset to false:
>
>
> MyDragDropManager>>dragStartAt: aPoint
>    dragging ifTrue:[ ^nil ].
>    dragging := true.
>    [
>        [ dragging ] whileTrue:[
>            Processor yield.
>            dropSource showDragShape.
>        ].
>    ] forkAt: Processor userBackgroundPriority - 1.
>
> MyDropSource>>showDragShape
>    (shape notNil and:[ offset notNil ]) ifTrue:[
>        Screen default
>            displayShape: shape
>            at: InputState default mousePoint - offset
>            forMilliseconds: 20.          ].
>
> In the previous version, I included a delay in the inner loop of  
> the background process, because other processes were disturbed by  
> drag &drop actions. I didn't realize that I simply needed to reduce  
> the process priority. Removing the delay and lowering the process  
> priority also removed the flicker ;-)
>
> Although the shape is only visible for 20ms, the human eye is too  
> slow to recognize that. The overall impression is a smooth move.
>
> Andre
>
>
> Andre Schnoor wrote:
>> Does anybody have an idea how to drag a (rectangular) shape over  
>> the whole screen? I'm using this for a drag & drop feature to  
>> indicate the object's size and exact drop location.
>>
>> My current implementation goes like this:
>>
>>        Screen default
>>            displayShape: shape
>>            at: InputState default mousePoint - offset
>>            forMilliseconds: 100.  whereby the shape is initialized  
>> with aPointArray. This however creates really annoying flicker.  
>> How can a shape be dragged smoothly?
>>
>> Any suggestion is appreciated.
>>
>> Andre
>>
>>
>>
>
>

> Andre,
>
> are you aware of the library methods for this on the class Screen?
> Their selectors all start with #drag...
>
>
> R
> -
>
>
>
>
> On Jan 20, 2007, at 9:59 AM, Andre Schnoor wrote:
>
>> Sorry for the noise. I just discovered one possible solution myself
>> (see code below).
>>
>> MyDragDropManager is a subclass of DragDropManager extended by an
>> instance variable bearing the dragged shape. After the drop, the flag
>> "dragging" is reset to false:
>>
>>
>> MyDragDropManager>>dragStartAt: aPoint
>>    dragging ifTrue:[ ^nil ].
>>    dragging := true.
>>    [
>>        [ dragging ] whileTrue:[
>>            Processor yield.
>>            dropSource showDragShape.
>>        ].
>>    ] forkAt: Processor userBackgroundPriority - 1.
>>
>> MyDropSource>>showDragShape
>>    (shape notNil and:[ offset notNil ]) ifTrue:[
>>        Screen default
>>            displayShape: shape
>>            at: InputState default mousePoint - offset
>>            forMilliseconds: 20.          ].
>>
>> In the previous version, I included a delay in the inner loop of the
>> background process, because other processes were disturbed by drag
>> &drop actions. I didn't realize that I simply needed to reduce the
>> process priority. Removing the delay and lowering the process
>> priority also removed the flicker ;-)
>>
>> Although the shape is only visible for 20ms, the human eye is too
>> slow to recognize that. The overall impression is a smooth move.
>>
>> Andre
>>
>>
>> Andre Schnoor wrote:
>>> Does anybody have an idea how to drag a (rectangular) shape over the
>>> whole screen? I'm using this for a drag & drop feature to indicate
>>> the object's size and exact drop location.
>>>
>>> My current implementation goes like this:
>>>
>>>        Screen default
>>>            displayShape: shape
>>>            at: InputState default mousePoint - offset
>>>            forMilliseconds: 100.  whereby the shape is initialized
>>> with aPointArray. This however creates really annoying flicker. How
>>> can a shape be dragged smoothly?
>>>
>>> Any suggestion is appreciated.
>>>
>>> Andre
>>>
>>>
>>>
>>
>>
>
>