Solved

Need help with Paint problems with .NET control (PictureBox)

Posted on 2004-10-17
12
661 Views
Last Modified: 2012-08-13
I have a simple application where I'm using GDI+ objects to draw text onto a PictureBox. In the form's Paint method, I've got a call to redraw the text and that works fine when you move a window through the PictureBox.

However, if you move another window on top of the PictureBox, then switch back to my application, the PictureBox redraws that area to the default background colour after my form paint code runs.

What is the proper way to make sure that a control gets repainted when needed?
0
Comment
Question by:tma050898
  • 6
  • 2
  • 2
  • +2
12 Comments
 
LVL 48

Expert Comment

by:Mikal613
ID: 12333876
autoredraw = false
0
 
LVL 3

Author Comment

by:tma050898
ID: 12333934
Where exactly is this property? I don't see any property having to do with drawing on the PictureBox property list.
0
 
LVL 48

Expert Comment

by:Mikal613
ID: 12334106
on the form
0
Resolve Critical IT Incidents Fast

If your data, services or processes become compromised, your organization can suffer damage in just minutes and how fast you communicate during a major IT incident is everything. Learn how to immediately identify incidents & best practices to resolve them quickly and effectively.

 
LVL 28

Expert Comment

by:iboutchkine
ID: 12337510
.NET does not have autoredraw property. VB6 does
0
 
LVL 3

Author Comment

by:tma050898
ID: 12338310
When I looked at  he other person's bio, I kinda figured it was a vb thing. Hopefully, someone here will know the answer for .NET. (Not sure if it matters in terms of winforms, but I'm using Managed C++).
0
 
LVL 96

Expert Comment

by:Bob Learned
ID: 12338782
What does the code for the Paint event look like?

Bob
0
 
LVL 3

Author Comment

by:tma050898
ID: 12338832
private: System::Void Form1_Paint(System::Object *  sender,
                                                   System::Windows::Forms::PaintEventArgs *  e)
{
  PaintText();
}

protected: System::Void PaintText()
{
  if (textToDisplay)
  {
    // Create the font that will be used.
    System::Drawing::Font* font =
      new System::Drawing::Font(S"Times New Roman",
        Convert::ToSingle(fontSize), FontStyle::Regular);

    // Create a Graphics object from the picture box
    Graphics* g = picText->CreateGraphics();

    // Clear the picture box using a white background so that
    // the gradient and hatch text shows up best
    g->Clear(Color::White);

    // Measure the user-supplied text
    SizeF textSize = g->MeasureString(textToDisplay, font);

    // Create the GDI+ brush
    Brush* brush;
    if (TextStyle::Hatch == style)  // if the user selected Hatch
    {
      // GDI+ supplies a HatchBrush object.
      // I'm using the built-in "cross hatch" pattern
      brush = new HatchBrush(HatchStyle::Cross, primaryColour, secondaryColour);
    }
    else if (TextStyle::Gradient == style) // if the user selected Gradient
    {
      // Instantiate a LinearGradientBrush object.
      // I'm using the built-in "forward-diagonal" gradient
      RectangleF* rect = __nogc new RectangleF(PointF(0, 0), textSize);
      brush = new LinearGradientBrush(*rect,  primaryColour, secondaryColour,
                                                        LinearGradientMode::ForwardDiagonal);
    }

    // Now that we have a brush, simply draw the text using DrawString!!
    g->DrawString(textToDisplay, font, brush,
                          (picText->Width - textSize.Width) / 2,
                          (picText->Height - textSize.Height) / 2);
  }
}
0
 
LVL 96

Accepted Solution

by:
Bob Learned earned 500 total points
ID: 12338862
Use the Graphics from the e.Graphics argument (persistent), instead of the CreateGraphics method (non-persistent).

Bob
0
 
LVL 3

Author Comment

by:tma050898
ID: 12339023
Bingo. Here's what I did (for future searches of this help)

1) I changed my button routine to the following
  * setup some internal display variables
  * call picText->Invalidate();
2) Added an event handler for the PictureBox control's (picText) Paint event
3) Moved the form's paint code (that painted the picText control into the picText::Paint method
4) Per "TheLearnedOne's" advice, I then used the PaintEventArgs::Graphics object

Works perfectly. Thanks much.
0
 
LVL 3

Author Comment

by:tma050898
ID: 12339065
One last question. Should I be disposing of these objects at some pt (via obj->Dispose) ?
0
 
LVL 85

Expert Comment

by:Mike Tomlinson
ID: 12343971
To answer your last question:

If YOU create a graphics, brush or pen using CreateGraphics or the NEW keyword, then YOU need to dispose of it.  If you use the supplied graphics in the "e" argument then you DO NOT need need to dispose it.

~IM
0
 
LVL 3

Author Comment

by:tma050898
ID: 12344380
So in this case I should be releasing the Font, then. Thanks!
0

Featured Post

How Do You Stack Up Against Your Peers?

With today’s modern enterprise so dependent on digital infrastructures, the impact of major incidents has increased dramatically. Grab the report now to gain insight into how your organization ranks against your peers and learn best-in-class strategies to resolve incidents.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Summary Displaying images in RichTextBox is a common requirement with limited solutions available. Pasting through clipboard or embedding into RTF content only support static images.  This article describes how to insert Windows control objects int…
The object model of .Net can be overwhelming at times – so overwhelming that quite trivial tasks often take hours of research. In this case, the task at hand was to populate the datagrid from SQL Server database in Visual Studio 2008 Windows applica…

809 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question