Beijer Electronics (formerly QSI Corporation)

Manufacturer of Mobile Data and Human Machine Interface Terminals.
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PostPosted: Fri Jan 26, 2007 2:27 pm 
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Location: Salt Lake City, Utah
I suspect that this is just the tip of the iceberg when it comes to the Qlarity rendering engine, but I wanted to share a couple of thoughts.



This particular scenario is very difficult for customers to code around:



The application is about to perform a time intensive operation and needs to inform the user to expect a delay, perhaps by setting a label's caption, before it begins the operation.



The user has to perform the following steps:

    * Create a custom user message.

    * Set the label's caption.

    * Override the label's Draw() function (assuming that the object he is using has an overridable Draw).

    * In the overriden draw, post a UserDirectMsg somewhere indicating that the draw has completed

    * Handle the custom user message and perform the operation



From a usage standpoint this is a real pain. From a tech support standpoint, this is a pain to describe to even moderately bright users.



At an absolute minimum, we should an API which will force any pending draw messages to complete before it returns. (From a technical standpoint, this shouldn't be much more difficult than the current UserSendMsg API with DoNow set to true).



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Some other things that would be nice from an object design standpoint:

    * An option for an object to not have to start from scratch when it draws (i.e. when MSG_DRAW is called, it already has the results of its last draw in tact, so the object could only draw changes)

    * The ability to "erase" portions of an object during a MSG_DRAW. In effect to opaquely draw the transparent color over the object.

    * Some sort of ability to draw directly to a canvas or a pixmap. We have this very crudely in place with the MSG_DRAW_TO_PIXMAP, but that has a number of limitations (such as cannot be done during a MSG_DRAW).

    * The ability to scale pixmaps & bitmaps

    * For drawing purposes, it might be nice if Area Object's origin were (0,0) instead of (xPos, yPos) -- Ron, do you have some feedback here? Would it be confusing if the object used it's parent's coordinates for placement, and its own zero based coordinates for drawing? Containers already do this.

    * DrawBox (and other APIs) would take a width and height instead of a right and bottom. This is easier for objects, which already track their width and height, but don't usually track their right and bottom position.





Edit 29 Jan: Fixed formatting. Added DrawBox suggestion to suggestions list

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PostPosted: Tue Jan 30, 2007 11:00 am 
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Joined: Thu Mar 02, 2006 2:12 pm
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Location: Salt Lake City, Utah
Yes, its confusing for an internal objects drawing code to not start from 0,0. I also prefer using Width & Height VS. Right and Bottom.

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Ron L.

http://www.beijerelectronicsinc.com/


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