Hi, I am designing a CAD application using a variation of MVC architecture. My model and view are independent of each other. They communicate through the controller. My problem is if I need to draw an object (say line or polyline) I need a number of input points. What would be the best way to get the points? All the events from the view are subscribed by the controller and controller has to keep the points, then generate the line or polyline and finally add this line to view. But I dont know how capturing the mouse points be done efficiently, because each object will have different number of inputs and different algorithms of input validations. Any help would be highly appreciated.
A:
when designing a CAD software, you must not only think of flexibility and dynamic, but also of speed. You should use some kind of wrapper class that works as a very thin layer between you and the hardware driver, it should return stuff like the pixel array of the screen, the current bpp, etc... This is how I would do it (and did actually). Now in C#, seeing as it is a .NET language, I'm not sure you can go that below, but you can still have someking of handler between the controller and your pen object, can't you?
Ricardo Ferreira
2010-02-23 18:27:46
yes, thats right. But I am using a thrid party tool as the draw control. user will be picking the points on this control and I need to get the points and call the control's method to draw the line. As the controller is listening to the events from the view control, the controller will get the mouse events and has to store the input points. I was asking how this can be done in a better way. Plz ask me if my question is not clear.
CadPro
2010-02-23 18:47:43
+1
A:
I was working in a CAD application 3 years ago, and these are some tips I remembered we have done (BTW: the application is free, you can download it, register your copy, and make use of the features in the Truss Editor):
1- You may add buttons for shape drawing, example: a button for a line, a button for a polyline, a rectangle, ...etc.
2- Create a variable that holds the current state your application (may be an enum): ready, drawing point, drawing line, drawing polyline, drawing circle, ...etc.
3- Wherever the user clicks a drawing button, the system enters a relevant state from those mentioned above.
4- The system returns to the "ready mode" when finished drawing, which can be detected automatically by the expected number of points (1 for point, 2 for line, 3 for ellipse, ...etc) or when the user presses Esc or right-clicked the drawing area (if the expected number of points is unknown, example: polyline). You may also end polyline drawing if the user re-clicked the first point and he has drawn 3+ points.
5- The system may cancel current drawing operation if the user ends the operation before completing the number of expected points.
...
Sameh Serag
2010-02-23 22:10:02