Change the color of a rectangular area on mouse over.

Question

5.00/5 (2 votes)

See more:

I have a rectangle which is drawn in the WM_PAINT message. Now I want to simulate this rectangular portion like a button. When I bring the mouse cursor into the rectangular area its background color should be changed and when i bring the cursor out of it it should be in its original color.

How can I catch this mouse-over event using Win32 API ? I suspect many mouse messages must be used to overcome this. However i am succesful in catching the mouse-in effect as follows:

C++

//The rectangle is just a structure with 4-values(x1, y1, x2, y2).
case WM_MOUSEMOVE:
   int x = LOWORD(lParam);
   int y = HIWORD(lParam);

   if(X_and_Y_are_inside_the_rectangle)
   {
      //get_a_dc
      //paint_the_rectangle_with_another_color
      //release_dc
   }
   else
   {
      //if i uncomment the following line even the mouse-in effect 
      //won't work
      
      //InvalidateRect(hwnd, NULL, TRUE);
   }
return 0;

case WM_PAINT:
    //get_a_dc
    //paint_the_rectangle_with_original_color
    //release_dc
    return 0;

Question in Brief:
How can I catch the mouse-in and mouse-out events of a particular rectangular area in Win32 API ?

The Only problem is with catching these 2 king of messages and not with anything else like the GDI library.

Posted 23-Dec-13 5:12am

Codexzy

Add a Solution

2 solutions

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Codexzy · Accepted Answer · 2013-12-24T21:23:00

C++

#define INSIDE_RECT   1
#define OUTSIDE_RECT -1

static int iHoverRect;

case WM_CREATE:
    iHoverRect = OUTSIDE_RECT;
    return 0;

case WM_MOUSEMOVE:
    int x = LOWORD(lParam);
    int y = HIWORD(lParam);

    if(iHoverRect == OUTSIDE_RECT)
    {
        if(is_points_in_rect)
        {
            iHoverRect = INSIDE_RECT;
            //mouse-in event here
        }
    }
    else
    {
        if(!is_points_in_rect)
        {
            iHoverRect = OUTSIDE_RECT;
            //mouse-out event here
        }
    }

    return 0;

CPallini · Accepted Answer · 2013-12-23T06:54:00

Solution 1

You should draw only inside WM_PAINT message handler. For instance (pseudo-code):

C

case WM_MOUSEMOVE:
   int x = LOWORD(lParam);
   int y = HIWORD(lParam);

   if(X_and_Y_are_inside_the_rectangle)
   {
     if ( colorRect != colorInside)
     {
        colorRect = colorInside;
        InvalidateRect
        UpdateWindow
     }
   }
   else
   {
     if ( colorRect != colorOutside)
     {
        colorRect = colorOutside;
        InvalidateRect
        UpdateWindow
     }
   }
return 0;

case WM_PAINT:
    get_a_dc
    paint the rectangle with colorRect
    release_dc
    return 0;

Posted 23-Dec-13 6:54am

CPallini

Comments

Codexzy 25-Dec-13 3:26am

Thank You. Actually I thought about this method and this works correctly. However I found a more optimized solution. Please see my answer below !

CPallini 25-Dec-13 4:48am

It looks pretty the same. Am I missing something?

Codexzy 28-Dec-13 23:44pm

Yes both are pretty much the same, but there is a slight difference. If I am to hit-test more than one rectangle, you'll see that my method is a little more efficient.