C / C++ / MFC

How do I Dynamically Draw Lines with the Mouse

13-Mar-04 22:36

What you are trying to do is basic thing

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Re: start button

Michael P Butler13-Mar-04 22:23

Michael P Butler

13-Mar-04 22:23

Your question is a little vague.

Is this what you are looking for?

http://www.microsoft.com/msj/archive/S274.aspx[^]

Michael

But you know when the truth is told,
That you can get what you want or you can just get old,
Your're going to kick off before you even get halfway through.
When will you realise... Vienna waits for you? - "The Stranger," Billy Joel

Re: start button

gonenb16-Mar-04 21:02

gonenb

16-Mar-04 21:02

ill try to be explain what i need a little better.

im a software engineer in the embedded market working on a multi-media co-processor
during development , we have an evaluation board to test this processor( it has an embedded arm processor), this board is something like a small computer , it can run applications, and has a filesystem, and has many configurations.

my company uses a very ugly interface to test it, and as a side project i wanna rewrite the interface, currently is looks like giant dialog box with many buttons, and is very hard to understand.

my idea was to write a program that will look like windows, the main window will have
a start button, pressing it will open a dialog that will give me choises of the applications + button for control panel to change the different configurations.
one application will be file explorer that will look like windows explorer but the file system will be the one on the evaluation board.

if you got better idea how the interface should look or how can i implement it please help.

Gonen

Re: Console Application

Branislav13-Mar-04 3:48

Branislav

13-Mar-04 3:48

#include "stdafx.h"
#include <windows.h> // Sleep
#include <conio.h> // _getch, kbhit

#include <iostream>
using namespace std;

int main(int argc, char* argv[])
{
int state = 0;
int exit = 0;

while(1)
{
if(kbhit())
{
exit = _getch();
if(exit == 27) // ESC
break;
}

if(state == 0)
cout<< "\n STOP.\n";
else if(state == 1)
cout<< "\n Prepare to GO.\n";
else if(state == 2)
cout<< "\n GO.\n";
else if(state == 3)
cout<< "\n Prepare to STOP.\n";
state++;
if(state == 4) state = 0;
Sleep(1000);
}
return 1;
}

Anonymous12-Mar-04 18:57

Anonymous

12-Mar-04 18:57

I am currently trying to write a simple program that allows the user to click in the "view" to define the start of a line, draw a line from the start to the mouse (where ever the mouse moves to and while it moves) and then complete the line when the user clicks in the view again.

The only hangup that I'm having is that after I click in the view and begin to move the mouse, I end up drawing lines to everywhere the mouse goes and eventually the screen looks a mess with lines all over it. I understand why this happens, I just don't know how not to make it happen.

In psuedocode, my code goes something like this.

OnLButtonDown
CreateStartPoint
GetScreenCoord
OnMouseMove(POINT point)
LineTo(StartPoint, point)
OnLButtonDown
CreateEndPoint
GetScreenCoord
LineTo(StartPoint,EndPoint)

I'm missing something to "brush" over the old mouse position each time OnMouseMove is called. I've looked at some sample code but haven't been able to get it to work.
Other samples have mentioned using Memory DC's and Storing the view as a Bitmap.

Anyone out there got a simple solution?

I'm fairly confident that once someone explains how to accomplish this, I'll be able to figure out the rest.

Thanks

Re: How do I Dynamically Draw Lines with the Mouse

Prakash Nadar12-Mar-04 19:46

Re: How do I Dynamically Draw Lines with the Mouse

12-Mar-04 19:46

There is a sample project called as DRAW that comes with VC installation.
This project will provide all the inputs needed for ur application.

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Anonymous13-Mar-04 19:45

Anonymous

13-Mar-04 19:45

I don't have a "DRAW" sample. I have a "DRAWCLI" sample.
If these are the same then I know what you're talking about. However, the code isn't very portable and is way to complex for what I'm trying to do. The DRAWCLI sample uses OLE and ties the drawtool objects into the drawview cview so tightly that it becomes very difficult to pull just the drawtool object into a project and put it to use. Eventually I suppose I could trim the code down and disect it to where it fit my needs.

Re: How do I Dynamically Draw Lines with the Mouse

Christopher Lloyd13-Mar-04 8:08

Christopher Lloyd

13-Mar-04 8:08

An easy solution is to use an XOR pen. When you draw your line it'll be XORed with whatever is already on the screen. When the mouse moves draw the previous line again using the XORed pen (this will remove the previous line) and then draw the new line, again using the XORed pen.
This works because XOR is it's own inverse.
To actually code this you'll need to use the api function SetROP2 before drawing. This determines how GDI merges pens (and some other drawing objects too) with what's already on the screen.
The only disadvantge is that an XOR pen isn't a solid colour, rather it appears as the inverse of the colour on the screen. Of course, this might actually be a good thing as it ensures your line is always visible no matter what you draw over.
Hope that helps.

CALLBACK

Shi Zhu12-Mar-04 18:01

Shi Zhu

12-Mar-04 18:01

hello,Please tell me what CALLBACK doing?thanks.

human

l a u r e n12-Mar-04 20:21

l a u r e n

12-Mar-04 20:21

callback functions are static functions in your code that the operating system calls to notify you of some condition, such as a timer firing

"there is no spoon"
biz stuff about me

Prakash Nadar12-Mar-04 22:29

12-Mar-04 22:29

l a u r e n wrote:
callback functions are static functions in your code

callback functions are not static functions... It is defined as follows

#define CALLBACK    __stdcall

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Rickard Andersson²⁰12-Mar-04 23:49

12-Mar-04 23:49

Think twice, what about in C++?

Rickard Andersson
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Prakash Nadar13-Mar-04 1:54

13-Mar-04 1:54

Well i did do some RnD before posting tht , as long as it is VC++ i dont think its a static function unless i missed something.
or you could show me something that says its static.

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Prakash Nadar13-Mar-04 3:19

13-Mar-04 3:19

Rickard Andersson19 wrote:
Think twice

surely in VC++ CALLBACK is not a static function at all.

and

Rickard Andersson19 wrote:
what about in C++?

Is VC++ not C++ ??
so really i dont know which C++ compiler you are talking about, but in VC++ callback is not a static function, its only a calling convention.

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Rickard Andersson²⁰13-Mar-04 5:30

13-Mar-04 5:30

Mr.Prakash wrote:
Is VC++ not C++ ??

Sigh | :sigh:

VC++ is a compiler. C++ is a language.

In C++ (the language) you must declare a method as static before you can use as a callback.

Rickard Andersson
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Prakash Nadar13-Mar-04 5:51

13-Mar-04 5:51

Rickard Andersson19 wrote:
VC++ is a compiler. C++ is a language.

VC++ compiles code writen in C++ so If you write something in C++ that VC++ cannot compile then its not a VC++ code.
what ever that meant.

using static functions as callback is one thing and in VC++
CALLBACK is different not callback but CALLBACK (something the original poster has asked the question about).
I hope now its clear.

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Rickard Andersson²⁰13-Mar-04 5:58

13-Mar-04 5:58

Mr.Prakash wrote:
VC++ compiles code writen in C++ so If you write something in C++ that VC++ cannot compile then its not a VC++ code.
what ever that meant.

You can write C code. And LRESULT CALLBACK Name(...) is a callback declaration of a C function callback, not C++. lauren said it's a static function, and because this is a (V)C++ forum C++ is the first hand language so a callback function is a static function (member function actually).

Mr.Prakash wrote:
and in VC++ CALLBACK is different not callback but CALLBACK (something the original poster has asked the question about).
I hope now its clear.

if so, lauren explained what a callback was? not the defination of CALLBACK...

Rickard Andersson
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Sonork: 37318

Prakash Nadar13-Mar-04 14:11

13-Mar-04 14:11

Rickard Andersson19 wrote:
if so, lauren explained what a callback was? not the defination of CALLBACK...

lauren said its a static function, which is wrong(it can be a static function but not neccessary).
lauren said what is callback function, that is correct.

no wonder the author of the post had given a low grade to that ans.

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Rickard Andersson²⁰13-Mar-04 14:17

13-Mar-04 14:17

Mr.Prakash wrote:
lauren said its a static function, which is wrong

In C++ it's not.

Mr.Prakash wrote:
lauren said what is callback function, that is correct.

What do you mean?
Your English is almost impossible to understand sometimes.

Rickard Andersson
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Sonork: 37318

Shi Zhu13-Mar-04 1:15

Shi Zhu

13-Mar-04 1:15

thanks,Would you give me CALLBACK example.

human

Gary R. Wheeler13-Mar-04 5:45

Gary R. Wheeler

13-Mar-04 5:45

A CALLBACK function is a function in your code that Windows calls to tell you about an event or an item of interest.

Here is an example. The Windows API function EnumWindows enumerates the top-level windows. You pass it a pointer to a CALLBACK function. Windows calls that function once for each top-level window:

BOOL CALLBACK MyFunction(HWND hwnd,LPARAM lParam)
{
    //...
    return TRUE;
}

// somewhere else in your code:

    EnumWindows(MyFunction,0);

The function MyFunction is a callback function. When you call EnumWindows, Windows will call MyFunction for each top-level window in the system.

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